349 28 Lab-manual Lab-manual Op Amp 3e LabManual

Operational Amplifiers & Linear Ics, 3/e

David A. Bell

Laboratory Manual for

Operational Amplifiers and Linear ICs Third Edition

David A. Bell Lambton College of Applied Arts and Technology, Sarnia, Ontario, Canada

© Oxford University Press 2011


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Preface This laboratory manual is designed to support the theory explained in my book Operational Amplifiers and Linear ICs. A total of twenty-one laboratory investigations are offered involving the construction and testing of circuits discussed in the text book. Each investigation consists of: . a title . an introduction that briefly describes the investigation . a list of required equipment and components . circuit diagrams and connection diagrams . a step-by-step procedure to be followed . a laboratory record sheet for recording data . an analysis section for processing the data Each laboratory investigation can normally be completed within a two hour period. The procedures contain some references to the textbook; however, all necessary circuit and connection diagrams are provided in the manual, so the investigations can be performed without using the textbook. David Bell.



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Contents 1

Basic Op-amp Circuits

2

Op-amp Parameters

3

Direct Coupled Amplifiers

4

Summing and Difference Circuits

5

Instrumentation Amplifier

6

Capacitor Coupled Voltage Followers

7

Capacitor Coupled Amplifiers

8

Use of Single-Polarity Supplies

9

Amplifier Bandwidth and Compensation

10

Slew Rate Effects

11

Schmitt Trigger Circuits

12

Differentiation and Integration

13

Precision Rectification, Clipping, and Clamping

14

Astable and Monostable Multivibrators

15

Triangular Waveform Generator

16

Timer Astable and Monostable Circuits

17

Sinusoidal Oscillators

18

Low-Pass and High-Pass Filters

19

Band-Pass Filters

20

Series Voltage Regulators

21

Power Amplifier


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Laboratory Investigation 1

BASIC OP-AMP CIRCUITS Introduction Three basic op-amp circuits are investigated: a voltage follower, a noninverting amplifier, and an inverting amplifier. Each circuit is tested with dc input voltages, and then with ac inputs. The output voltage levels are measured, and the amplitude and phase relationships between input and output are noted. Equipment Plus-minus DC Power Supply—(0 to ±30 V, 50 mA) DC Power Supply—(0 to 12 V, 50 mA) Two DC Voltmeters Oscilloscope Sinusoidal Signal Generator—(1 kHz, ±5 V) Circuit Board Op-amp—741 or similar alternative 0.25 W resistors—(2 × 56 kΩ), 8.2 kΩ, 270 Ω, 150 Ω, (2 × 68 Ω)

Procedure 1 Voltage Follower 1-1 Connect an op-amp as a voltage follower as shown in Fig. 1-1. Connect the power supply, dc voltage source, voltmeters, and oscilloscope, as illustrated. 1-2 Set the power supply voltage to ±12 V, and adjust the voltmeters as necessary to monitor the op-amp dc input and output voltage levels.



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Figure 1-1 Voltage follower circuit and connection diagram.

1-3 Adjust the input voltage to +1 V, +2 V, and +3 V in turn. In each case, record the output voltage on the laboratory record sheet. 1-4 Repeat Procedure 1-3 using levels of –1 V, –2 V, and –3 V. 1-5 Disconnect the dc source, substitute the signal generator in its place, and apply a ±5 V, 1 kHz sinusoidal input signal. Adjust the oscilloscope to monitor the ac input and output of the circuit. 1-6 Measure the circuit ac output voltage and the input/output phase relationship. 1-7 Adjust the signal amplitude to ±2 V and ±3 V in turn, and measure the output in each case. Record the results on the laboratory record sheet. Procedure 2 Noninverting Amplifier 2-1 Connect an op-amp as a noninverting amplifier as shown in Fig. 1-2. Connect the power supply, dc voltage source, voltmeters, and oscilloscope as illustrated. 2-2 Set the power supply voltage to ±12 V. Note that the resistors are R1 = 8.2 kΩ and R2 = 150 Ω, as in the first part of Example 1-3 in the text book. 2-3 Adjust the input voltage to +50 mV and 75 mV in turn. In each case, record the output voltage on the laboratory record sheet, and calculate the voltage gain. 2-4 Repeat Procedure 2-3 using input levels of –50 mV and –75 mV. 2-5 Disconnect the dc source, and substituting the signal generator in its place, apply a ±25 mV, 1 kHz sinusoidal input signal. 2-6 Record the circuit output voltage and the input/output phase relationship. 2-7 Adjust the input voltage to ±50 mV. Record the output amplitude and calculate the voltage gain.



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2-8 Change R3 to approximately 111 Ω (use two series-connected 56 Ω resistors), as in the second part of Example 1-3 in the text book. 2-9 Repeat Procedure 2-7.

Figure 1-2 Noninverting amplifier circuit and connection diagram.

Procedure 3 Inverting Amplifier 3-1 Connect an op-amp as an inverting amplifier as shown in Fig. 1-3. Connect the power supply, dc voltage source, voltmeters, and oscilloscope as illustrated. 3-2 Set the power supply voltage to ±12 V. Note that the resistors are R1 = 8.2 kΩ and R2 = 270 kΩ, as in the first part of Example 1-4 in the text book. 3-3 to 3-7 Repeat Procedure 2-3 through 2-7. 3-8 Change R2 to approximately 137 Ω (use two series-connected 68 Ω resistors), as in the second part of Example 1-4 in the text book. 3-9 Repeat Procedure 2-7.



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Figure 1-3 Inverting amplifier circuit and connection diagram.

Analysis 1 2

3

Discuss the voltage follower input and output voltage amplitudes and phase relationships. Discuss the noninverting amplifier input and output voltage amplitudes and phase relationships. Compare the experimental results to the calculated values in Example 1-3 in the text book. Discuss the inverting amplifier input and output voltage amplitudes and phase relationships. Compare the experimental results to the calculated values in Example 1-4 in the text book.



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OP-AMP PARAMETERS Introduction An op-amp is connected to function as an inverting amplifier with its input grounded. The output offset voltage is measured and the input offset voltage is calculated. With the op-amp connected as a voltage follower, the process of output offset nulling is investigated. The input bias current is determined by inserting a resistor in series with each input terminal, in turn, and measuring the resultant output voltage change. Input and output voltage ranges are checked by increasing the amplitude of a sinusoidal input signal until peak clipping occurs. The op-amp open-loop gain is determined by us of a modified inverting amplifier circuit. Equipment Plus-minus DC Power Supply—(0 to ±30 V, 50 mA) DC Power Supply—(0 to 12 V, 50 mA) Two DC Voltmeters Oscilloscope Sinusoidal Signal Generator—(100 Hz, ±15 V) Circuit Board Op-amp—741 or similar alternative 0.25 W resistors—10 Ω, 100 Ω, 1.5 kΩ, 5.6 kΩ, 10 kΩ, (2 × 100 kΩ), 1 MΩ Potentiometer—10 kΩ

Procedure 1 Offset Voltage Measurement 1-1 Connect an op-amp as an inverting amplifier with the input grounded as shown in Fig. 2-1. Connect the power supply and voltmeter as illustrated. 1-2 Set the power supply to ±12 V, record the measured output offset voltage on the laboratory record sheet, and calculate the input offset voltage. 1-3 Calculate the input offset voltage due to the specified maximum input bias current: (IB(max) × 10 Ω). Compare this to the input offset voltage determined from the measurements to check that it does not introduce a significant error.



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Figure 2-1 Circuit and connection diagram for offset voltage measurement.

Procedure 2 Input Bias Current and Offset Currents 2-1 Connect a 741 op-amp as a voltage follower with a nulling potentiometer and the input grounded as shown in Fig. 2-2. Connect the power supply and voltmeters as illustrated.

Figure 2-2 Circuit and connection diagram for offset nulling investigation.



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2-2 Set the power supply voltage to ±12 V, and adjust the nulling potentiometer to give zero output voltage. If the output cannot be completely nulled, record the Vo level. 2-3 Switch off the supply, remove the grounding connection from the op-amp noninverting input terminal, and reconnect it to ground via a 1 MΩ resistor. 2-4 Switch the supply on again, and note the change in output voltage ∆Vo (from the Vo nulled level). Calculate the input bias current at the op-amp noninverting terminal. 2-5 Switch off the supply, remove the connection from the op-amp inverting input to the output, and reconnect it to the output via a 1 MΩ resistor. Ground the noninverting input directly once again. 2-6 Switch the supply on again, and note the change in output voltage ∆Vo (from the nulled level). Calculate the input bias current at the op-amp inverting input. 2-7 Calculate the input offset current.

Procedure 3 Input and Output Voltage Ranges 3-1 Connect an op-amp voltage follower circuit as in Fig. 2-3 using 100 kΩ resistors in series with each input terminal, as illustrated. Set the power supply voltage to ±9 V. 3-2 Connect a sinusoidal signal generator to the voltage follower input, and an oscilloscope to monitor the input and output as shown. Note that the oscilloscope is connected right at the op-amp noninverting input terminal. 3-3 Apply a 100 Hz sine wave input and increase its amplitude until the output waveform peaks just begin to flatten.

Figure 2-3 Circuit and connection diagram for input voltage range investigation.



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3-4 Measure the input wave positive and negative peak levels to determine the op-amp input voltage range. 3-5 Reconnect the op-amp as an inverting amplifier as in Fig. 2-4 using R1 = 10 kΩ, R2 = 100 kΩ, and a ±9 V supply. 3-6 Apply a 100 Hz sine wave input and increase its amplitude until the output waveform peaks just begin to flatten. 3-7 Measure the output wave positive and negative peak levels to determine the op-amp output voltage range.

Figure 2-4 Circuit and connection diagram for output voltage range investigation.

Procedure 4 Open-Loop Voltage Gain 4-1 Construct the op-amp circuit illustrated in Fig. 2-5 using the components shown. Connect the ±12 V supply and voltmeters to monitor Vo and V3. 4-2 Adjust the dc voltage source at the circuit input to give an op-amp output of Vo = – 10 V. 4-3 Record the V3 voltage level, and calculate the op-amp differential input. 4-4 Calculate the op-amp open-loop voltage gain.



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Figure 2-5 Circuit and connection diagram for determining the open-loop gain.

Analysis 1

2

3

Compare the measured input offset voltage to the specified input offset voltage for the op-amp. Comment on the input offset voltage due to the maximum input bias current. Compare the measured input bias current and the measured input offset current to the quantities specified for the op-amp. Calculate the maximum resistance value that should be used at the input terminals of the op-amp. Compare the measured input and output voltage ranges to the op-amp specified ranges. Briefly explain the cause of the limits on the input and output voltage swings.



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Compare the experimentally determined open-loop voltage gain with the quantities specified for the op-amp. Briefly explain the operation of the circuit in Fig. 2-5.



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DIRECT COUPLED AMPLIFIERS Introduction Several direct-coupled noninverting and inverting amplifier circuits designed in examples in the text book are investigated. Tests are performed to determine the input/output voltage relationships and to check input and output impedances. Equipment Plus-minus DC Power Supply—(0 to ±15 V, 50 mA) Oscilloscope Sinusoidal Signal Generator—(1 kHz, ±15 mV) Circuit Board Op-amp—741, LF353 (or alternatives with similar specifications) 0.25 W resistors—100 Ω, (2 × 270 Ω), (3 × 1 kΩ), (2 × 15 kΩ), (2 × 18 kΩ), 47 kΩ, (2 × 1 MΩ), Capacitors—20 µF

Procedure 1 Direct-Coupled Noninverting Amplifier 1-1 Construct the 741 noninverting amplifier shown in Fig. 3-1 using the component values determined in Example 3-3 in the text book. Connect the power supply, signal generator, and oscilloscope as illustrated. 1-2 Set the power supply voltage to ±15 V, and adjust the signal generator to produce a ±15 mV, 1 kHz sinusoidal input to the amplifier. 1-3 Measure the amplitudes of the input and output waveforms, record the measured quantities on the laboratory record sheet, and calculate the amplifier closed-loop voltage gain. 1-4 Connect a 1 MΩ resistor in series with the amplifier input. Check that the output voltage is unaffected, to demonstrate that Zin >> 1 MΩ. 1-5 Capacitor-couple a 100 Ω resistor in parallel with the op-amp output using a 20 µF capacitor. Check that the output voltage is unaffected, to show that Zout << 100 Ω. 1-6 Construct the LF353 noninverting amplifier shown in Fig. 3-2 using the component values determined in Example 3-4 in the text book. (Note that the pin connections for the 353 are different from those for the 741.) 1-7 Repeat Procedures 1-2 through 1-5.



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Figure 3-1 Noninverting amplifier using a 741 op-amp.



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Figure 3-2 Noninverting amplifier using an LF353 op-amp.

Procedure 2 Direct-Coupled Inverting Amplifier 2-1 Construct the 741 inverting amplifier shown in Fig. 3-3 using the component values determined in Example 3-6 in the text book. Connect the power supply, signal generator, and oscilloscope as illustrated. 2-2 Set the power supply voltage to ±15 V, and adjust the signal generator to produce a ±2.5 V, 1 kHz sinusoidal output from the amplifier. 2-3 Measure and record the amplitude of the input waveform, and calculate the amplifier closed-loop voltage gain. 2-4 Connect a 1 kΩ resistor in series with the amplifier input. Note that the output voltage is halved, to show that Zin = R1. 2-5 Remove the series-connected resistor at the input and capacitor-couple a 100 Ω resistor in parallel with the output using a 20 µF capacitor. Check that the output voltage is unaffected, to show that Zout << 100 Ω. 2-6 Construct the LF353 noninverting amplifier shown in Fig. 3-4 using the component values determined in Example 3-7 in the text book. 2-7 Repeat Procedures 2-2 and 2-3.



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2-8 Connect an 18 kΩ resistor in series with the amplifier input. Note that the output voltage is halved, to show that Zin = R1. 2-9 Repeat Procedure 2-5.

Figure 3-3 Inverting amplifier using an 741 op-amp.



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Figure 3-4 Inverting amplifier using an LF353 op-amp.

Analysis Compare the performance of each of the amplifiers investigated to the design objectives in the appropriate text book examples.



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SUMMING AND DIFFERENCE CIRCUITS Introduction A summing circuit and a difference amplifier are investigated, both designed in text book examples. In each case various input voltages are applied and the output is monitored to check the input/output relationships. Equipment Plus-minus DC Power Supply—(0 to ±15 V, 50 mA) Three DC Power Supplies—(0 to 12 V, 50 mA) Three DC Voltmeters Circuit Board Op-amp—741, LF353 (or alternatives with similar specifications) 0.25 W resistors—560 Ω, (3 × 1.8 kΩ), 18 kΩ, (2 × 27 kΩ), (2 × 1 MΩ) Procedure 1 Direct-Coupled Summing Circuits 1-1 Construct the inverting summing circuit shown in Fig. 4-1, using a 741 op-amp and the component values determined in Example 3-9 in the text book. 1-2 Connect the power supply, adjustable dc voltage sources, and voltmeters, as illustrated, and set the power supply to ±15 V. 1-3 Set V1 and V2 to the voltage levels shown for Procedure 1-3 on the laboratory record sheet, and record the output voltages in each case. 1-4 Change R3 to 18 kΩ and repeat the process using the levels listed for Procedure 1-4 on the laboratory record sheet

Figure 4-1 Two-input inverting summing circuit.



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Figure 4-2 Difference amplifier.

Procedure 2 Direct-Coupled Difference Amplifier 2-1 Construct the difference amplifier shown in Fig. 4-2 using an LF353 op-amp and the component values determined in Example 3-10 in the text book. 1-2 Connect the power supply, adjustable dc voltage sources, and voltmeters, as illustrated, and set the power supply to ±15 V. 2-3 Set V1 and V2 to the voltage levels shown for Procedure 2-3 on the laboratory record sheet, and record the output voltages in each case. 2-4 Ground the two input terminals and connect an adjustable dc bias source (VB) between R4 and ground, as illustrated in Fig. 4-3(a). 2-5 Investigate the adjustable dc bias source as a level shifter, recording its voltage level and the resultant output voltage. 2-6 Remove the dc source and voltmeter from R4, ground R4 once again. Connect the two input terminals together and connect the adjustable dc source (as a commonmode input) to both inputs, as illustrated in Fig. 4-3(b). 2-7 Set the common mode input to 10 V, record the output voltage level, and calculate the common mode gain.



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Figure 4-3 Difference amplifier modifications to investigate output level shifting and common mode gain.



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Analysis 1 2 3

Use Eq. 3-10 in the text book to calculate the output voltage levels for each set of inputs for the summing circuit. Compare the calculated and measured quantities. Use Eq. 3-12 in the text book to calculate the output voltage levels for each set of inputs for the difference amplifier. Compare the calculated and measured quantities. Discuss the measured common mode gain for the difference amplifier.



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INSTRUMENTATION AMPLIFIER Introduction An instrumentation amplifier is constructed and tested. Common mode gain, differential gain, common mode nulling, and output level shifting are all investigated. Each stage gain is checked with various input voltages. Equipment Plus-minus DC Power Supply—(0 to ±15 V, 50 mA) Two DC Power Supplies—(0 to 12 V, 50 mA) Two DC Power Voltmeters—(0 to ±15 V) Oscilloscope Sinusoidal Signal Generator—(1 kHz, ±15 mV) Circuit Board Op-amps—(3 × 741) Resistors—(2 × 27 kΩ), (3 × 12 kΩ) Potentiometers—350 Ω, 10 kΩ

Procedure 1 Common Mode Voltage Gain and Level Shifting 1-1 Construct the instrumentation amplifier circuit shown in Fig. 5-1 using a ±15 V supply and the component values determined in Example 3-12 in the text book. (Note the use of decoupling capacitors C1 and C2 to ensure circuit stability.) 1-2 Set R2 and R7 for maximum resistance, and set the dc offset voltage (VB) to zero. 1-3 Temporarily disconnect R4 and R6 from the outputs of A1 and A2, connect them together, and apply a 5 V input. Adjust R7 to produce 0 V dc output from A3. 1-4 Disconnect the 5 V input from R4 and R6 and reconnect the resistors to A1 and A2 once again. Do not alter R7 or VB. 1-5 Ground the A1 and A2 noninverting inputs, and record the level of Vo from A3. 1-6 Adjust VB to +1 V, +2 V, and +3 V in turn, and record the A3 output voltage in each case. 1-7 Adjust VB to set Vo3 to zero, reversing the polarity of VB if necessary. Record the level of VB. 1-8 Apply a +5 V common mode input to the A1 and A2 noninverting inputs, and record the output voltage from each op-amp.



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Figure 5-1 Instrumentation amplifier



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Procedure 2 Differential Gain Ground the A2 noninverting input terminal and apply +10 mV to the A1 input. Adjust R2 until Vo3 = 4 V. Record the op-amp output voltages (Vo1, Vo2, and Vo3.). Reverse the polarity of the A1 input voltage, and record Vo1, Vo2, and Vo3. Ground the A1 noninverting input terminal and apply +10 mV to the A2 input. Record Vo1, Vo2, and Vo3. 2-5 Reverse the polarity of the A2 input voltage, and record Vo1, Vo2, and Vo3. 2-6 Apply +5 mV to the A1 input and –5 mV to the A2 input and note the new levels of Vo1, Vo2, and Vo3. 2-7 Switch of the supply voltage, and disconnect R2 without altering its setting. Measure and record the R2 resistance.

2-1 2-2 2-3 2-4

Figure 5-2 AC testing.

Procedure 3 AC Operation 3-1 Reconnect R2, ground R7 and the A2 input, and connect a sinusoidal signal generator and oscilloscope as illustrated in Fig. 5-2. 3-2 Apply a 100 Hz, 10 mV peak sine wave input. Measure and record the peak output voltage from A1, A2, and A3.

Analysis 1

Compare the slew rate determined in Procedure 1-3 with that specified for a 741 opamp.



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From the results of Procedure 1-8, Calculate the common mode gain for the circuit. From the Procedure 2-2 and 2-3 results, calculate each stage gain and the overall differential gain. Compare these to the quantities in Example 3-12 in the text book. Discuss the results of Procedures 2-4 through 2-6. Compare the measured resistance of R2 with the calculated value in Example 3-12 in the text book. Determine the common mode rejection ratio for the circuit. Explain the results of the ac measurements made in Procedure 3-2.



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CAPACITOR COUPLED VOLTAGE FOLLOWERS Introduction Two capacitor-coupled voltage follower circuits designed in examples in the text book are constructed and tested. Both circuits are tested for operation at 1 kHz, then the lower cutoff frequency is determined. The input impedances of the circuits are also investigated. Equipment Plus-minus DC Power Supply—(0 to ±15 V, 50 mA) Oscilloscope Sinusoidal Signal Generator—(10 Hz to 10 kHz) Circuit Board Op-amp—741 Resistors—3.9 kΩ, (2 × 68 kΩ), (2 × 120 kΩ), 1 MΩ Capacitors—0.27 µF, (2 × 0.5 µF), 0.39 µF, 0.82 µF

Procedure 1 Capacitor Coupled Voltage Follower 1-1 Construct the capacitor coupled voltage follower circuit shown in Fig. 6-1 using the component values determined in Example 4-1 in the text book. Connect the power supply, signal generator, and oscilloscope as illustrated. 1-2 Set the power supply voltage to ±15 V, and adjust the signal generator to produce a ±1 V, 1 kHz sinusoidal input to the amplifier. Record the output voltage amplitude on the laboratory record sheet and calculate the voltage gain. 1-3 Maintaining the input voltage constant, reduce the signal frequency until vo ≈ 0.707 vi. Record the lower cutoff frequency (f1). 1-4 Return the signal frequency to 1 kHz. Connect a 120 kΩ in series with the amplifier input. Check the effect on the output voltage and calculate Zin. 1-5 Remove the 120 kΩ resistor and replace C2 with a 0.39 µF capacitor. Repeat Procedure 1-3.

Procedure 2 High Zin Capacitor Coupled Voltage Follower 2-1 Construct the high input impedance capacitor coupled voltage follower circuit shown in Fig. 6-2 using the component values determined in Example 4-3 in the text book. Connect the power supply, signal generator, and oscilloscope as illustrated. 2-2 Repeat Procedures 1-2 and 1-3.



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2-3 Return the signal frequency to 1 kHz. Connect a 1 MΩ in series with the amplifier input. Check that the output voltage is unaffected, to demonstrate that Zin >> 1 MΩ.

Figure 6-1 Capacitor coupled voltage follower.



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Figure 6-2 High input impedance capacitor coupled voltage follower.

Analysis 1

2 3

Discuss the performance of each circuit in relation to the specified performance in the design examples. Consider the effect of component tolerance on the lower cutoff frequency. Explain the result of Procedure 1-5. Calculate the new capacitor values for the circuit of Fig. 6-1 if C1 is to set the lower cutoff frequency. Briefly explain how capacitor C2 in Fig. 6-2 affects the circuit input impedance.



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CAPACITOR COUPLED AMPLIFIERS Introduction Three capacitor-coupled amplifier circuits are constructed and tested: a noninverting amplifier, a high input impedance noninverting amplifier, and an inverting amplifier. All three circuits are tested for voltage gain, input impedance, and lower cutoff frequency. The upper cutoff frequency of the inverting amplifier is also investigated. Equipment Plus-minus DC Power Supply—(0 to ±15 V, 50 mA) Oscilloscope Sinusoidal Signal Generator—(10 Hz to 10 kHz) Circuit Board Op-amp—741, LF353 (or alternatives with similar specifications) Resistors—27 Ω, 220 Ω, 270 Ω, 1 kΩ, 2.2 kΩ, 4.7 kΩ, 12 kΩ, 18 kΩ, 47 kΩ, 120 kΩ, (3 × 1 MΩ) Capacitors—680 pF, 0.1 µF, 0.12 µF, 0.18 µF, 0.68 µF, 75 µF, 180 µF

Procedure 1 Capacitor Coupled Noninverting Amplifier 1-1 Construct the capacitor coupled noninverting amplifier circuit shown in Fig. 7-1 using the component values determined in Example 3-3 and 4-4 in the text book. Connect the power supply, signal generator, and oscilloscope as illustrated.



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Figure 7-1 Capacitor coupled noninverting amplifier.

1-2 Set the power supply voltage to ±15 V, and adjust the signal generator to produce a ±50 mV, 1 kHz sinusoidal input (vi) to the amplifier. Record the output voltage amplitude (vo) on the laboratory record sheet and calculate the amplifier gain. 1-3 Maintaining the input voltage constant, reduce the signal frequency until vo approximately equals 0.707 of the vo level at f = 1 kHz. Record the lower cutoff frequency (f1). 1-4 Return the signal frequency to 1 kHz. Connect a 120 kΩ in series with the amplifier input. Check the effect on the output voltage and calculate Zin.

Procedure 2 High Zin Capacitor Coupled Noninverting Amplifier 2-1 Construct the noninverting amplifier circuit shown in Fig. 7-2 using the component values determined in Example 4-5 in the text book. Connect the power supply, signal generator, and oscilloscope as illustrated. (It may be necessary to connect a 20 pF capacitor in parallel with R2 for circuit stability.) 2-2 Repeat Procedures 1-2 and 1-3 using a 15 mV signal amplitude. 2-3 Return the signal frequency to 1 kHz. Connect a 1 MΩ in series with the amplifier input. Check that the output voltage is unaffected, to demonstrate that Zin >> 1 MΩ.



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Figure 7-2 High input impedance capacitor coupled noninverting amplifier.

Procedure 3 Capacitor Coupled Inverting Amplifier 3-1 Construct the inverting amplifier circuit shown in Fig. 7-3 using the component values determined in Examples 3-6 and 4-6 in the text book. Connect the power supply, signal generator, and oscilloscope as illustrated. 3-2 Repeat Procedures 1-2 and 1-3. 3-3 Still maintaining the input voltage constant, increase the signal frequency until vo approximately equals 0.707 of the vo level at f = 1 kHz. Record the upper cutoff frequency (f2). 3-4 Return the signal frequency to 100 Hz. Connect a 1 kΩ in series with the amplifier input. Check the effect on the output voltage and calculate Zin.



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Figure 7-3 Capacitor coupled inverting amplifier.

Analysis 1

2

Discuss the performance of each of the noninverting amplifiers in relation to the specified performance in the design examples. Consider the effect of component tolerance on the lower cutoff frequency. Calculate the new capacitor values for the circuit of Fig. 7-1 if C1 is to set the lower cutoff frequency.



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Discuss the result of Procedure 2-3. Briefly explain how capacitor C2 in Fig. 7-2 affects the circuit input impedance. Discuss the performance of the inverting amplifier in relation to the specified performance in the design examples.



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USE OF SINGE-POLARITY SUPPLIES Introduction An inverting and a noninverting amplifier, both using single-polarity supply voltages, are tested for voltage gain and frequency response. The effect of input bias voltage change is also investigated. Equipment Plus-minus DC Power Supply—(0 to 30 V, 50 mA) Oscilloscope Sinusoidal Signal Generator—(10 Hz to 10 kHz) Circuit Board Op-amp—741 Resistors—250 Ω, 1 kΩ, 5.6 kΩ, 47 kΩ, (3 × 100 kΩ), (3 × 220 kΩ) Capacitors—680 pF, 0.2 µF, 2.2 µF, 3.9 µF, 75 µF, 180 µF

Procedure 1 Inverting Amplifier 1-1 Construct the inverting amplifier circuit shown in Fig. 8-1 using the component values determined in Example 3-6 and 4-6 in the text book. Use a +30 V supply and R3 = R4 = 100 kΩ. 1-2 Connect the signal generator, and oscilloscope as illustrated.



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Figure 8-1 Inverting amplifier circuit using a single-polarity supply.

1-3 Adjust the signal generator to produce a ±50 mV, 1 kHz sinusoidal input (vi) to the amplifier. Record the output voltage amplitude (vo) on the laboratory record sheet and calculate the amplifier gain.



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1-4 Maintaining the input voltage constant, reduce the signal frequency until vo approximately equals 0.707 of the vo level at f = 1 kHz. Record the lower cutoff frequency (f1). 1-5 Still maintaining the input voltage constant, increase the signal frequency until vo approximately equals 0.707 of the vo level at f = 1 kHz. Record the upper cutoff frequency (f2). 1-6 Set the signal voltage to zero, then use the oscilloscope to measure the dc voltage level at the junction of R3 and R4 and at the op-amp output. 1-7 Connect another 100 kΩ resistor in parallel with R4 to alter the bias voltage at the op-amp noninverting input terminal. 1-8 Repeat Procedure 1-6. 1-9 Repeat procedure 1-3. Procedure 2 High Zin Capacitor Coupled Noninverting Amplifier 2-1 Construct the noninverting amplifier circuit shown in Fig. 8-2 using the component values determined in Example 4-7 in the text book. Use a +24 V supply. 2-2 Connect the signal generator, and oscilloscope as illustrated. 2-3 Apply a 1 kHz sinusoidal input and adjust its amplitude to give a 5 V peak output. Record the input voltage amplitude (vi) on the laboratory record sheet and calculate the amplifier gain.



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Figure 8-2 Noninverting amplifier circuit using a single-polarity supply.



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2-4 Maintaining the input voltage constant, reduce the signal frequency until vo approximately equals 0.707 of the vo level at f = 1 kHz. Record the lower cutoff frequency (f1). 2-5 Set the signal voltage to zero, then use the oscilloscope to measure the dc voltage level at the junction of R1 and R2 and at the op-amp output. 2-6 Connect another 220 kΩ resistor in parallel with R2 to alter the bias voltage at the op-amp noninverting input terminal. 2-7 Repeat Procedure 2-5. 2-8 Repeat procedure 2-3.

Analysis 1 2 3 4

Discuss the voltage gain and cutoff frequencies for the inverting amplifier in relation to the specified performance in the design examples. Comment on the dc level measurements made for Procedures 1-5 through 1-8, and on the effect of changing the bias voltage. Discuss the voltage gain and cutoff frequencies for the noninverting amplifier in relation to the specified performance in the design examples. Comment on the dc level measurements made for Procedures 2-5 through 2-7, and on the effect of changing the bias voltage.



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AMPLIFIER BANDWIDTH AND COMPENSATION Introduction Three inverting amplifiers using three different op-amps are investigated for voltage gain and bandwidth. Equipment Plus-minus DC Power Supply—(0 to ±15 V, 50 mA) Oscilloscope Sinusoidal Signal Generator—(100 Hz to 1 MHz) Circuit Board Op-amps—LM 108, 741, LF353 (or alternatives with similar specifications) Resistors—(2 × 1 kΩ), 100 kΩ Capacitors—3 pF, 30 pF

Procedure 1 Bandwidth of an Amplifier Using an LM108 1-1 Construct the inverting amplifier circuit shown in Fig. 9-1. Use a ±15 V supply, and connect the signal generator, power supply, and oscilloscope as illustrated.



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Figure 9-1 Inverting amplifier circuit using an LM108 op-amp.

1-2 Adjust the signal generator to produce a 1 kHz sinusoidal input and adjust it to give a 100 mV peak output. Record the input voltage amplitude on the laboratory record sheet and calculate the amplifier gain. 1-3 Maintaining the input voltage constant, increase the signal frequency until vo approximately equals 0.707 of the vo level at f = 1 kHz. Record the upper cutoff frequency (f2). 1-4 Change Cf to 30 pF and repeat procedures 1-2 and 1-3.

Procedure 2 Bandwidth of an Amplifier Using a 741 2-1 Replace the LM108 in Fig. 9-1(b) with a 741, and remove capacitor Cf. 2-2 Repeat procedures 1-2 and 1-3. 2-3 Change resistor R2 to 47 kΩ, and repeat procedures 1-3 and 1-4 once again.

Procedure 3 Bandwidth of an Amplifier Using an LF353 3-1 Construct the inverting amplifier circuit shown in Fig. 9-2. Use a ±15 V supply, and connect the signal generator, power supply, and oscilloscope as illustrated. 3-2 Repeat procedures 1-2 and 1-3.



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Figure 9-2 Inverting amplifier using an LF353 op-amp.

Analysis 1 2 3

4

Comment on the measured mid-frequency voltage gains for all three amplifiers. Compare the LM108 circuit upper cutoff frequencies measured for Procedures 1-2 and 1-4 with those determined in Example 5-5 in the text book. Referring to Fig. 5-9 in the text book, estimate the cutoff frequencies for the 741 op-amp circuit for ACL = –100 and for ACL = –47. Compare to the measured results for Procedures 2-2 and 2-3. Using the LF353 circuit cutoff frequency determined for Procedure 3-3, calculate the op-amp GBW, and compare it to the specified GBW for an LF353.



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SLEW RATE EFFECTS Introduction A 741 voltage follower is constructed and tested to determine slew rate, small signal cutoff frequency, and slew rate limited cutoff frequency. Two noninverting amplifier, one using a 741 and one using a 353, are constructed and tested for the same quantities. Equipment Plus-minus DC Power Supply—(0 to ±15 V, 50 mA) Oscilloscope Function Generator (sine and square wave)—(100 Hz to 1 MHz) Circuit Board Op-amps—LM 108, 741, LF353 (or alternatives with similar specifications) Resistors—(2 × 1 kΩ), (2 × 10 kΩ), 47 kΩ, (2 × 100 kΩ), 1 MΩ

Procedure 1 Slew Rate Effects on a 741 Voltage Follower 1-1 Construct the inverting amplifier circuit shown in Fig. 10-1. Use a ±15 V supply, and connect the signal generator, power supply, and oscilloscope as illustrated.

Figure 10-1 Voltage follower circuit using a 741 op-amp.

1-2 Adjust the signal generator to produce a 10 kHz, ±5 V square wave.



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1-3 Measure the rise time (tr) of the circuit output waveform. Record tr on the laboratory record sheet, and calculate the slew rate. 1-4 Replace the square wave with a 1 kHz sinusoidal wave, and adjust the sine wave amplitude to give a 100 mV peak-to-peak output. 1-5 Maintaining the input voltage constant, increase the signal frequency until vo equals 70.7 mV p-to-p at the circuit upper cutoff frequency (f2). Record f2. 1-6 Reset the signal frequency to 1 kHz, and adjust the sine wave amplitude to give a ±5 V output. 1-7 Maintaining the input voltage constant, increase the signal frequency until vo falls to ±(0.707 × 5 V) at the slew rate limited cutoff frequency (fS). Record fS.

Figure 10-2 Noninverting amplifier using a 741 op-amp.

Procedure 2 Slew Rate Effects on a 741 Noninverting Amplifier 2-1 Construct the 741 noninverting amplifier circuit shown in Fig. 10-2. Use a ±15 V supply, and connect the signal generator, power supply, and oscilloscope as illustrated.



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2-2 Apply a 5 kHz square wave input, and adjust its amplitude to produce a ±5 V circuit output. 2-3 Measure the rise time (tr) of the circuit output waveform. Record tr on the laboratory record sheet, and calculate the slew rate. 2-4 Replace the square wave with a 1 kHz sinusoidal wave, and adjust the sine wave amplitude to give a 100 mV p-to-p output. 2-5 Maintaining the input voltage constant, increase the signal frequency until vo equals 70.7 mV p-to-p at the circuit upper cutoff frequency (f2). Record f2. 2-6 Reset the signal frequency to 1 kHz, and adjust the sine wave amplitude to give a ±10 V output. 2-7 Maintaining the input voltage constant, increase the signal frequency until vo falls to ±7.07 V at the slew rate limited cutoff frequency (fS). Record fS. 2-2 Change resistor R2 to 47 kΩ, and repeat procedures 2-4 through 2-7.

Figure 10-3 Noninverting amplifier using an LF353 op-amp.



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Procedure 3 Slew Rate Effects on an LF353 Noninverting Amplifier 3-1 Construct the LF353 noninverting amplifier circuit shown in Fig. 10-3. Use a ±15 V supply, and connect the signal generator, power supply, and oscilloscope as illustrated. 3-2 Apply a 100 kHz square wave input, and adjust its amplitude to produce a ±5 V circuit output. 3-3 Measure the rise time (tr) of the circuit output waveform. Record tr on the laboratory record sheet, and calculate the slew rate. 3-4 Replace the square wave with a 1 kHz sinusoidal wave, and adjust the sine wave amplitude to give a 100 mV p-to-p output. 3-5 Maintaining the input voltage constant, increase the signal frequency until vo equals 70.7 mV p-to-p at the circuit upper cutoff frequency (f2). Record f2. 2-6 Reset the signal frequency to 1 kHz, and adjust the sine wave amplitude to give a ±10 V output. 2-7 Maintaining the input voltage constant, increase the signal frequency until vo falls to ±7.07 V at the slew rate limited cutoff frequency (fS). Record fS.

Analysis 1 2 3 4 5

6 7 8 9

10

Compare the slew rate determined in Procedure 1-3 with that specified for a 741 opamp. Estimate the cutoff frequency for a 741 small signal voltage follower, and compare it to the f2 measured in Procedure 1-5. Calculate the slew rate limited cutoff frequency for the 741 voltage follower with a ±5 V output, and compare it to the measured result for Procedure 1-7. Compare the slew rate determined in Procedure 2-3 with that from Procedure 1-3. Estimate the cutoff frequency for the 741 noninverting amplifier from gain/frequency response Fig. 5-9 in the text book. Compare it to the cutoff frequency determined in Procedure 2-5. Calculate the slew rate limited cutoff frequency for the 741 noninverting amplifier with a ±10 V output, and compare it to the measured result for Procedure 2-7. Discuss the f2 and fS frequencies measured in Procedure 2-9. Compare the slew rate determined in Procedure 3-3 with that specified for an LF353 op-amp. Estimate the cutoff frequency for the LF353 noninverting amplifier from GBW specified on the op-amp data sheet. Compare it to the cutoff frequency determined in Procedure 3-5. Calculate the slew rate limited cutoff frequency for the LF353 noninverting amplifier with a ±10 V output, and compare it to the measured result for Procedure 2-7.



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SCHMITT TRIGGER CIRCUITS Introduction An inverting Schmitt trigger circuit is constructed and tested for upper and lower trigger points, and the output waveform is investigated. The circuit is modified by including a diode, then tested once again. A noninverting Schmitt trigger circuit is constructed and similarly investigated. Equipment Plus-minus DC Power Supply—(0 to ±15 V, 50 mA) Oscilloscope Function Generator (sine and triangular wave)—(1 kHz, ±8 V) Circuit Board Op-amps—741 Resistors—39 kΩ, 56 kΩ, 150 kΩ, 180 kΩ, 220 kΩ Diodes—(2 × 1N914)

Procedure 1 Inverting Schmitt Trigger 1-1 Construct the inverting Schmitt trigger circuit shown in Fig. 11-1(a) and (b) using the component values determine in Example 8-3 in the text book. Use a ±15 V supply, and connect the signal generator, power supply, and oscilloscope as illustrated. 1-2 Adjust the signal generator to produce a 1 kHz, ±5 V triangular wave input. 1-3 Sketch the input and output waveforms on the laboratory record sheet, and record the upper and lower trigger point voltages. 1-4 Adjust the amplitude of the input waveforms to ±6 V and ±5 V in turn. Measure and record the trigger point voltages in each case. 1-5 Change the input to a 1 kHz, ±5 V sinusoidal waveform. Once again sketch the input and output waveforms, and record the trigger voltages. 1-6 Modify the input by including diode D1 in series with R1, as in Fig 11-1(c). 1-7 Repeat Procedures 1-2 through 1-4.



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Figure 11-1 Inverting Schmitt trigger circuit.



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Figure 11-2 Noninverting Schmitt trigger circuit.



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Procedure 2 Noninverting Schmitt Trigger Circuit. 2-1 Construct the noninverting Schmitt trigger circuit shown in Fig. 11-2 using the component values from Fig. 8-15(b) in the text book. Use a ±15 V supply, and connect the signal generator, power supply, and oscilloscope as illustrated. 2-2 Adjust the signal generator to produce a 1 kHz, ±7 V triangular wave input. 2-3 Sketch the input and output waveforms on the laboratory record sheet, and record the upper and lower trigger point voltages. 2-4 Adjust the amplitude of the input waveforms to ±8 V and ±6 V in turn. Measure and record the trigger point voltages in each case. 2-5 Change the input to a 1 kHz, ±7 V sinusoidal waveform. Once again sketch the input and output waveforms, and record the trigger voltages.

Analysis 1 2 3 4 5

Compare the upper and lower trigger point voltages measured in Procedures 1-3 through 1-5 to the triggering levels used in Example 8-3 in the text book. Discuss the shape of the output waveforms obtained for Procedures 1-3 and 1-5. Discuss the output waveforms and triggering voltages obtained for Procedure 1-7. Compare the upper and lower trigger point voltages measured in Procedures 2-3 through 2-5 with the triggering levels determined in Example 8-4 in the text book. Discuss the shape of the output waveforms obtained for Procedures 2-3 through 2-5.



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DIFFERENTIATION AND INTEGRATION Introduction Differentiating and integrating circuits are constructed and tested for response to various input waveforms. The circuits use component values determined in Examples in the text book, so that their performances may be compared to the expected performances. Equipment Plus-minus DC Power Supply—(0 to ±15 V, 50 mA) Oscilloscope Triangular Wave Generator—(5 kHz, ±0.5 V) Square Wave Generator—(100 Hz to 500 Hz, ±0.5 to ±5 V) Sinusoidal Wave Generator—(100 Hz to 500 Hz, ±0.5) Circuit Board Op-amps—741, LF353 (or alternatives with similar specifications) Resistors—470 Ω, (2 × 10 kΩ), (2 × 12 kΩ), 270 kΩ Capacitors—0.05 µF, 0.1 µF

Procedure 1 Differentiating Circuit 1-1 Construct the differentiating circuit shown in Fig. 12-1 using the component values determine in Example 8-7 in the text book. Use a ±15 V supply, and connect the signal generator, power supply, and oscilloscope as illustrated. 1-2 Adjust the signal generator to produce a 5 kHz, ±0.5 V triangular wave input. 1-3 Sketch the input and output waveforms on the laboratory record sheet, and record the positive and negative peak voltage levels. 1-4 Replace the triangular wave input with a 100 Hz, ±0.5 V square wave. 1-5 Sketch the input and output waveforms on the laboratory record sheet, and record the positive and negative peak voltage levels. If possible, alter the rise and fall times of the square wave input and note the effect on the output. 1-6 Replace the square wave input with a 100 Hz, ±0.5 V sine wave. 1-7 Observe the input and output waveforms and note the phase relationship. 1-8 Slowly increase the sine wave frequency to discover the approximate frequency that causes the output to shift by 3° from the correctly differentiated output wave.



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Figure 12-1 Differentiating circuit.

Figure 12-2 Integrating circuit.



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Procedure 2 Integrating Circuit. 2-1 Construct the integrating circuit shown in Fig. 12-2 using the component values determined in Example 8-9 in the text book. Use a ±15 V supply, and connect the signal generator, power supply, and oscilloscope as illustrated. 2-2 Adjust the signal generator to produce a 500 Hz, ±5 V square wave input. 2-3 Sketch the input and output waveforms on the laboratory record sheet, and record the positive and negative peak voltage levels. 2-4 Replace the square wave input with a 500 Hz, ±0.5 V sinusoidal wave. 2-5 Observe the input and output waveforms and note the phase relationship. 2-6 Slowly reduce the sine wave frequency to discover the approximate frequency that causes the output to shift by 3° from the correctly differentiated output wave

Analysis 1 2 3 4

5

Compare the waveforms obtained for Procedures 1-3 to the waveforms in Fig. 825(a) in the text book. Compare the waveforms obtained for Procedures 1-5 to the waveforms in Fig. 825(b) and (c) in the text book. Comment on the input-output sine wave phase relationship observed for Procedure 1-7, and on the maximum differentiating frequency determined for Procedure 1-8. Compare the waveforms obtained for Procedures 2-3 to the waveforms in Fig. 8-31 in the text book. Compare the peak output voltage levels to the design levels in Example 8-8 in the text book. Comment on the input-output sine wave phase relationship observed for Procedure 2-5, and on the minimum integrating frequency determined for Procedure 2-6.



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PRECISION RECTIFICATION, CLIPPING, AND CLAMPING Introduction Saturating and nonsaturating precision half-wave rectifier circuits are constructed and tested. A precision clipping circuit with an adjustable clipping level is investigated, and a precision clamping circuit is tested for response to square wave inputs. Equipment Plus-minus DC Power Supply—(0 to ±15 V, 50 mA) Oscilloscope Sinusoidal Wave Generator—(1 kHz, ±15 mV) Square Wave Generator—(10 kHz, ±5 V) Circuit Board Op-amps—741, LF353 (or alternatives with similar specifications) Resistors—(2 × 470 Ω), 820 Ω, 1 kΩ, 1.5 kΩ, 2.2 kΩ, 3.9 kΩ, (2 × 22 kΩ) Capacitors—200 pF, 5000 pF, 0.5 µF Potentiometer—1 kΩ Diodes—(2 × 1N914) Zener Diodes—(2 × 1N749)

Procedure 1 Precision Half-wave Rectifiers 1-1 Construct the saturating precision rectifier circuit shown in Fig. 13-1. Use a ±15 V supply, and connect the sinusoidal signal generator, power supply, and oscilloscope as illustrated. 1-2 Adjust the signal generator to produce a 100 Hz, ±2 V sinusoidal wave input. Observe the half-wave rectified output waveform, and record its peak amplitude. 1-3 Switch the dc supply off, reverse the diode polarity, then switch the supply on again. 1-4 Repeat procedure 1-2. 1-5 Increase the signal frequency until the output becomes distorted. Record the frequency at which the rectifier circuit is still operating satisfactorily. 1-6 Construct the nonsaturating precision rectifier circuit shown in Fig. 13-2 using the component values determined in Example 9-1 in the text book. Use a ±15 V supply, and connect the sinusoidal signal generator, power supply, and oscilloscope as illustrated. 1-7 Repeat Procedure 1-2. 1-8 Switch the dc supply off, reverse the polarity of both diodes, then switch the supply on again. 1-9 Repeat Procedure 1-2.



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1-10 Repeat Procedure 1-5.

Figure 13-1 Saturating precision half-wave rectifier circuit.

Figure 13-2 Nonsaturating precision half-wave rectifier circuit.



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Procedure 2 Clipping Circuit. 2-1 Construct the clipping circuit shown in Fig. 13-3 using the component values determined in Example 9-4 in the text book. Use a ±15 V supply, and connect the signal generator, power supply, and oscilloscope as illustrated. 2-2 Adjust the signal generator to produce a 1 kHz, ±7 V sine wave input. 2-3 Observing the output waveform on the oscilloscope, slowly adjust the moving contact of R4 from one extreme to the other. Measure and record the clipped output voltage peaks at each extreme.

Figure 13-3 Adjustable clipping circuit.



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Figure 13-4 Clamping circuit.

Procedure 3 Precision Clamping Circuit. 3-1 Construct the clamping circuit shown in Fig. 13-4 using the component values determined in Example 9-7 in the text book. Use a ±12 V supply, and connect the signal generator, power supply, and oscilloscope as illustrated. 3-2 Adjust the signal generator to produce a 10 kHz, ±5 V square wave input. Measure and record the peak-to-peak output voltage, and note the positive peak relationship to ground level. 3-3 Switch the supply off, reverse the polarity of the diodes and of capacitor C1. 3-4 Switch the supply on again, and repeat Procedure 3-2.

Analysis 1 2

3

Comment on the results of Procedures 1-2 through 1-8. How might the performance of the saturating and nonsaturating circuits differ at high frequencies? Compare the results of Procedure 2-3 with the clipping range specified in Example 9-4. Show how the clipping circuit should be modified to clip off an adjustable portion of the positive half-cycle while reproducing the complete negative halfcycle. Comment on the input-output sine wave phase relationship observed for Procedure 1-7, and on the maximum differentiating frequency determined for Procedure 1-8.



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Comment on the results of Procedures 3-2 and 3-4. Explain how the clamping circuit should be modified to clamp the output peaks at voltage levels above or below ground.



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ASTABLE AND MONOSTABLE MULTIVIBRATORS Introduction An astable multivibrator and a monostable multivibrator designed in examples in the text book are constructed and tested. The output frequency of the astable is measured for comparison to the design frequency, and its capacitance value is altered to observe the resultant frequency change. The pulse width of the monostable output is measured, and its capacitance value is altered to investigate its effect on the pulse width. Equipment Plus-minus DC Power Supply—(0 to ±15 V, 50 mA) Oscilloscope Pulse Generator—(100 µs, 200 Hz, 2 V) Circuit Board Op-amp—LF353 (or alternative with similar specifications) Resistors—3.3 kΩ, 39 kΩ, 56 kΩ, 1 MΩ Capacitors—1100 pF, (2 × 0.1 µF) Diode—1N914

Procedure 1 Astable Multivibrator 1-1 Construct the astable multivibrator circuit shown in Fig. 14-1, using the component values determined in Example 10-1 in the text book. Use a ±10 V supply, and connect the power supply, and oscilloscope as illustrated. 1-2 Sketch the capacitor waveform and the output waveform on the laboratory record sheet, and record the waveform amplitudes and frequency. 1-3 Double the capacitance of C1 by paralleling it with another 0.1 µF capacitor. Record the effect on the waveform amplitudes and frequency. Procedure 2 Monostable Multivibrator. 2-1 Modify the astable multivibrator to convert it into the monostable multivibrator shown in Fig. 14-2, by including components D1 and C2 and the necessary connecting links. Connect the signal generator, as illustrated. 2-2 Adjust the signal generator to produce a 200 Hz, +2 V, 100 µs pulse wave input. 2-3 Sketch the input, output, and C1 waveforms on the laboratory record sheet, and record the waveform amplitudes and the output pulse width. 2-4 Double the capacitance of C1 by paralleling it with another 0.1 µF capacitor. Record the effect on the waveform amplitudes and the output pulse width.



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Figure 14-1 Astable multivibrator.

Figure 14-2 Monostable multivibrator

Analysis 1 2

3

Explain the astable capacitor and output waveforms obtained for the Procedure 1-2. Compare the frequency and waveform amplitudes measured in Procedure 1-2 with the design quantities in Example 10.1, and discuss the effects of doubling the capacitance value. Explain the monostable pulse width and waveform amplitude obtained for the Procedure 2-3.



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Comment on the pulse width and amplitude measurements made for Procedure 2-4. Discuss the operation of the astable multivibrator circuit, and explain how adding the diode converts it into a monostable.



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TRIANGULAR WAVEFORM GENERATOR Introduction A triangular waveform generator designed in an example in the text book is constructed and tested. The output amplitude and frequency are monitored, and the effects of component changes are measured. The circuit is modified for duty cycle adjustment, and further modified to convert it into a voltage controlled oscillator. The output waveforms are investigated in each case. Equipment Plus-minus DC Power Supply—(0 to ±15 V, 50 mA) DC Power Supply—(0 to 12 V, 50 mA) DC Voltmeter Oscilloscope Circuit Board Op-amps—(3 × 741) (or alternative with similar specifications) Resistors—3.9 kΩ, 18 kΩ, (2 × 22 kΩ), (2 × 33 kΩ), 82 kΩ, (2 × 120 kΩ) Capacitors—(2 × 0.015 µF) Diodes—(2 × 1N914) Potentiometer—200 kΩ

Procedure 1 Triangular Wave generator Circuit 1-1 Construct the triangular waveform generator circuit shown in Fig. 15-1, using the component values determined in Example 10-4 in the text book. Use a ±15 V supply, and connect the power supply, and oscilloscope as illustrated. 1-2 Switch on the power supply, and monitor the output waveform from each section of the circuit. Sketch the waveforms on the laboratory record sheet, and record the waveform amplitudes and frequency. 1-3 Double the capacitance of C1 by paralleling it with another 0.015 µF capacitor. Record the effect on the amplitude and frequency of the output waveforms. 1-4 Remove the additional capacitor from C1, and halve the resistance of R2 by paralleling it with another 18 kΩ resistor. Record the effect on the amplitude and frequency of the output waveforms. Procedure 2 Duty Cycle Adjustment 2-1 Switch off the supply, and modify the triangular wave generator for duty cycle adjustment as shown in Fig. 15-2. Note that the component values used are from Example 10-5 in the text book.



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2-2 Switch the supply on again, and adjust R5 to give the largest resistance in series with R6. 2-3 Measure the frequency, pulse width, and time period of the rectangular wave. Record these quantities on the laboratory record sheet, and calculate the duty cycle. 2-4 Adjust R5 to give the largest resistance in series with R7, and repeat Procedure 2-3.

Figure 15-1 Triangular waveform generator circuit.

Figure 15-2 Modification for duty cycle adjustment.



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Procedure 3 Voltage Controlled Triangular Wave Generator 3-1 Switch the supply off, and modify the circuit to convert it into a voltage controlled oscillator, using the component values determined in Example 10-6 in the text book, as illustrated in Fig. 15-3. 3-2 Switch the supply on again, and adjust VB to 9.5 V. 3-3 Record the amplitudes and frequency of the output waveforms. 3-4 Adjust VB to 7.5 V and 3.5 V in turn, and repeat Procedure 3-3 in each case.

Figure 15-3 Voltage controlled triangular wave generator.

Analysis 1

2 3 4

Discuss waveforms obtained in Procedure 1-2, and compare the measured frequency and amplitudes with the design quantities in Example 10-4 in the text book. Discuss the effects of doubling the capacitance of C1, and the effect of halving the resistance of R2, as for Procedures 1-3 and 1-4. Compare the duty cycle range measurements made for Procedure 2-3 and 2-4 to the design quantities in Example 10-5 in the text book. Compare the results for Procedure 3-3 and 3-4 with the frequency range specified in Example 10-6 in the text book. Discuss the voltage controlled circuit operation.



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TIMER ASTABLE AND MONOSTABLE CIRCUITS Introduction A timer astable multivibrator circuit designed in an example in the text book is constructed and tested. The circuit is then modified into an adjustable frequency square wave generator, which is then investigated for output waveform and frequency range. A timer monostable circuit is next constructed and triggered from the square wave generator. Finally, a sequential timer is constructed, and its output waveforms are investigated. Equipment DC Power Supply—(0 to 18 V, 50 mA) Oscilloscope Circuit Board Timers—(2 × 555) Resistors—1 kΩ, 2.7 kΩ, 3.3 kΩ, (2 × 10 kΩ), 180 kΩ Capacitors—5000 pF, 680 pF, (2 × 0.01 µF), 0.082 µF, (2 × 0.1 µF) Potentiometer—5 kΩ Diode—1N914

Procedure 1 Basic Timer Astable Multivibrator 1-1 Construct the 555 timer astable multivibrator circuit shown in Fig. 16-1, using the component values determined in Example 10-9 in the text book. Use a +15 V supply, and connect the power supply and oscilloscope as illustrated. 1-2 Switch on the power supply, and monitor the output waveform at terminal 3, and the waveform across capacitor C1. Sketch the waveforms on the laboratory record sheet, record their amplitudes, pulse widths, and space widths, and show their time relationships. 1-3 Adjust the supply voltage to 5 V, and once again record the waveform amplitudes pulse widths, and space widths. Procedure 2 Timer Square Wave Generator 2-1 Switch off the supply, and reconstruct the circuit as shown in Fig. 16-2. 2-2 Set the supply to 12 V and set R2 to zero. 2-3 Switch the supply on and monitor the output waveform at terminal 3 and the waveform across capacitor C1. Sketch the waveforms on the laboratory record sheet, record their amplitudes, pulse widths, and space widths, and show their time relationships.



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2-4 Adjust R2 to maximum resistance, and record the waveform amplitudes, pulse widths, and space widths.

Figure 16-1 Basic timer astable multivibrator.



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Figure 16-2 Timer square wave generator.

Procedure 3 Timer Monostable Multivibrator 3-1 Switch the supply off, and construct a monostable multivibrator capacitor-coupled to the square wave generator, as illustrated in Fig. 16-3. Note that the monostable component values are taken from Example 10-8 in the text book. 3-2 Set the supply to 12 V, and adjust R2 in the square wave generator to zero. 3-3 Switch the supply on, and monitor the monostable input and output waveforms. Sketch the waveforms on the laboratory record sheet, record their amplitudes, pulse widths, and space widths, and show their time relationships.



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Figure 16-3 Timer monostable multivibrator triggered from an astable.

Figure 16-4 Sequential timer.

Procedure 4 Sequential timer 4-1 Switch the supply off, and construct the astable multivibrator controlled from the square wave generator, as shown in Fig. 16-4. 4-2 Switch the supply on, and monitor the square wave generator output and the astable output. Sketch the waveforms on the laboratory record sheet, record their amplitudes, pulse widths, and space widths, and show their time relationships.



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Analysis 1 2

3

4

Compare the waveforms obtained for Procedures 1-2 and 1-3 to the design specifications in Example 10-9 in the text book. Discuss the square wave generator waveforms obtained for Procedures 2-3 and 2-4. Analyze the circuit to determine the maximum and minimum frequencies, and compare to the measured quantities. Explain the monostable multivibrator waveforms obtained for Procedure 3-3, and compare the measured output pulse width to the quantity specified in Problem 10-8 in the text book. Explain the pulsed tone oscillator waveforms obtained for Procedure 4-2.



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SINUSOIDAL OSCILLATORS Introduction A phase shift oscillator designed in an example in the text book is constructed and tested for output amplitude and frequency. The circuit is then modified to include voltage divider amplitude stabilization, and its output is further investigated. A quadrature oscillator is similarly investigated with and without amplitude stabilization. A Wein bridge oscillator, also designed in a text book example, is constructed and tested. In this case, diode amplitude stabilization is used, and its the effect on the output is measured. Equipment DC Power Supply—(0 to 18 V, 50 mA) Oscilloscope Circuit Board Op-amps—(2 × 714) (or alternative with similar specifications) Resistors—1.2 kΩ, (3 × 6.8 kΩ), (3 × 8.2 kΩ), 10 kΩ, (2 × 15 kΩ), (2 × 22 kΩ), (2 × 33 kΩ), (2 × 56 kΩ), (2 × 68 kΩ), (2 × 220 kΩ) Capacitors—(3 × 3300 pF), (3 × 0.01 µF) Diodes—(4 × 1N914)

Procedure 1 Phase Shift Oscillator 1-1 Construct the phase shift oscillator circuit shown in Fig. 17-1 leaving the diodes out of the circuit at this time. Use a ±12 V supply, and connect the power supply and oscilloscope as illustrated. 1-2 Switch on the power supply, and monitor the waveforms at the op-amp output and at the junction of R1 and C1. Sketch the waveforms on the laboratory record sheet and record their amplitude and frequency. 1-3 Switch the power supply off, and install the diodes to include the amplitude stabilization components in the circuit. 1-4 Switch the power supply on, and once again record the waveform amplitudes and frequency. Procedure 2 Quadrature Oscillator 2-1 Construct the quadrature oscillator circuit shown in Fig. 17-2 leaving the diodes out of the circuit at this time. Use a ±10 V supply, and connect the power supply and oscilloscope as illustrated. 2-2 Switch on the power supply, and monitor waveforms at the output of each op-amp and at the junction of R2 and C2. Sketch the waveforms on the laboratory record



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sheet showing their phase relationships and amplitude. Record the waveform amplitudes and frequency.

2-3 Switch the power supply off, and install the diodes to include the amplitude stabilization components in the circuit. 2-4 Switch the power supply on, and once again record the waveform amplitudes and frequency.

Figure 17-1 Phase shift oscillator.



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Figure 17-2 Quadrature oscillator.



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Procedure 3 Wein Bridge Oscillator 3-1 Construct the Wein bridge oscillator circuit shown in Fig. 17-3 leaving the diodes out of the circuit at this time. Use a ±10 V supply, and connect the power supply and oscilloscope as illustrated. 3-2 Switch on the power supply, and monitor the waveforms at the op-amp output and at its noninverting input. Sketch the waveforms on the laboratory record sheet and record their amplitude and frequency. 3-3 Switch the power supply off, and install the diodes to include the amplitude stabilization components in the circuit. 3-4 Switch the power supply on, and once again record the waveform amplitudes and frequency.

Figure 17-3 Wein bridge oscillator.

Analysis 1 2 3

4

Compare the waveforms obtained for Procedures 1-2 to the design quantities in Example 11-1 in the text book. Analyze the amplitude stabilized phase shift oscillator circuit to determine the expected output amplitude. Compare the calculated and measured quantities. Analyze the quadrature oscillator to determine the output frequency and the output amplitude with and without amplitude stabilization. Compare the calculated quantities to the measured quantities in Procedure 3. Compare the waveforms obtained for Procedures 3-2 to the design quantities in Example 11-3 in the text book.



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Compare the results obtained for Procedures 3-4 to the design quantities in Example 11-4 in the text book.



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Low-pass and High-pass Filters Introduction Two second-order filter circuits designed in examples in the text book are constructed and tested. A low-pass filter is tested for upper cutoff frequency and output falloff rate. A high-pass filter is tested for lower cutoff frequency, falloff rate, and circuit upper cutoff frequency. Equipment DC Power Supply — (±15 V, 50 mA) Oscilloscope Sinusoidal Signal Generator — (100 Hz to 11 MHz, ±1 V) Op-amps —(741, 108) (or alternative with similar specifications) Resistors —(4 × 4.7 kΩ), 18 kΩ, 33 kΩ, 39 kΩ Capacitors —30 pF, (2 × 1000 pF), 2000 pF, Circuit Board Procedure 1 Low-pass Filter 1-1 Construct the second-order low-pass filter circuit shown in Fig. 18-1 using the component values determined in Ex. 12-3 in the text book. 1-2 Before connecting the power supply, switch it on and adjust its output for VCC = ±12 V. Switch the power supply off, then connect it to the circuit and switch on. 1-3 Ground the circuit input and use the oscilloscope to check that the filter circuit is not oscillating, then connect the oscilloscope and signal generator as illustrated. 1-4 Adjust the signal generator to apply a ±1 V, 100 Hz sinusoidal input to the filter. Check that the output displayed on the oscilloscope is also ±1 V, 100 Hz. 1-5 Keeping the input amplitude constant, increase the signal frequency until the output level falls to approximately ±0.707 V. Record the filter upper cutoff frequency (fc) on the laboratory record sheet. 1-6 Increase the signal frequency to 2fc (keeping the input amplitude constant), then measure and record the new peak level of the output voltage. Procedure 2 High-pass Filter 2-1 Construct the second-order high-pass filter circuit shown in Fig. 18-2 using the component values determined in Example 12-4 in the text book. 2-2 Before connecting the power supply, switch it on and adjust its output for VCC = ±15 V. Switch the power supply off, then connect it to the circuit and switch on. 2-3 Ground the circuit input and use the oscilloscope to check that the filter circuit is not oscillating, then connect the oscilloscope and signal generator as illustrated.



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2-4 Adjust the signal generator to apply a ±1 V, 50 kHz sinusoidal input to the filter. Check that the output displayed on the oscilloscope is also ±1 V, 50 kHz. 2-5 Keeping the input amplitude constant, reduce the signal frequency until the output level falls to approximately ±0.707 V. Record the filter lower cutoff frequency (fc) on the laboratory record sheet. 2-6 Reduce the signal frequency to fc/2 (keeping the input amplitude constant), then measure and record the new peak level of the output voltage. 2-7 Increase the signal frequency through fc (keeping the input amplitude constant) until the output level falls to approximately ±0.707 V once again. Record the circuit upper cutoff frequency (f2) on the laboratory record sheet.

Fig. 18-1 Second-order low-pass filter circuit and connection diagram



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Fig. 18-2 Second-order high-pass filter circuit and connection diagram.

Analysis 1 2 3 4 5

Compare the low-pass filter cutoff frequency measured in Procedure 1-5 with the design quantity in Example 12-3 in the text book. Use the voltage levels measured in Procedures 1-5 and 1-6 to calculate the low-pass filter output falloff rate. Compare to the theoretical falloff rate. Compare the high-pass filter cutoff frequency measured in Procedure 2-5 with the design quantity in Example 12-4 in the text book. Use the voltage levels measured in Procedures 2-5 and 2-6 to calculate the highpass filter output falloff rate. Calculate the upper cutoff frequency for the high-pass filter, and compare it to the cutoff frequency measured in Procedure 2-7.



David A. Bell



David A. Bell

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BAND-PASS FILTERS Introduction Two band-pass filter circuits designed in examples in the text book are constructed and tested. A single-stage filter is tested to determine its upper and lower cutoff frequencies and the output falloff rate beyond these frequencies. A state-variable filter using three opamps is tested for center frequency and upper and lower cutoff frequencies. Equipment DC Power Supply — (±15 V, 50 mA) Oscilloscope Sinusoidal Signal Generator — (10 Hz to 100 kHz, ±1 V) Op-amps — (3 × 741) (or alternative with similar specifications) Resistors — (3 × 5.6 kΩ), (2 × 1 kΩ), (6 × 15 kΩ), 120 kΩ Capacitors —1000 pF, (2 × 0.01 µF), 0.1 µF Circuit Board

Procedure 1 Single Stage Band-Pass Filter 1-1 1-2 1-3

1-4 1-5

1-6 1-7

1-8

Construct the single-stage band-pass filter circuit shown in Fig. 19-1 using the component values determined in Example 12-7 in the text book. Before connecting the power supply, switch it on and adjust its output for VCC = ±12 V. Switch the power supply off, then connect it to the circuit and switch on. Ground the circuit input and use the oscilloscope to check that the filter is not oscillating, then connect the oscilloscope and signal generator to the circuit as illustrated. Adjust the signal generator to apply a ±1 V, 3 kHz sinusoidal input to the filter. Check that the output displayed on the oscilloscope is also ±1 V, 3 kHz. Keeping the input amplitude constant, decrease the signal frequency until the output level falls to approximately ±0.707 V. Record the filter lower cutoff frequency (f1) on the laboratory record sheet. Reduce the signal frequency to f1/2 (keeping the input amplitude constant), then measure and record the new peak level of the output voltage. Increase the signal frequency through 3 kHz (keeping the input amplitude constant) until the output level falls to approximately ±0.707 V once again. Record the filter upper cutoff frequency (f2) on the laboratory record sheet. Still maintaining the input amplitude constant, further increase the signal frequency to 2f2. Measure and record the new peak level of the output voltage.



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Procedure 2 State-Variable Band-Pass Filter 2-1 2-2 2-3

2-4

2-5

2-6

Construct the state-variable band-pass filter circuit shown in Fig. 19-2 using the component values determined in Example 12-11 in the text book. Before connecting the power supply, switch it on and adjust its output for VCC = ±15 V. Switch the power supply off, then connect it to the circuit and switch on. Ground the circuit input and use the oscilloscope to check that the filter is not oscillating, then connect the oscilloscope and signal generator to the circuit as illustrated. Adjust the signal generator to apply a ±0.1 V, 1 kHz sinusoidal input to the filter. Carefully adjust the frequency for maximum amplitude at the A2 output, which occurs at the filter center frequency (fo). Record fo and the output amplitude. Keeping the input amplitude constant, reduce the signal frequency until the output level falls to approximately ±0.707 V. Record the filter lower cutoff frequency (f1) on the laboratory record sheet. Increase the signal frequency through fo (keeping the amplitude constant) until the output level falls to approximately ±0.707 V once again. Record the filter upper cutoff frequency (f2) on the laboratory record sheet.

Fig. 19-1 Single-stage band-pass filter circuit and connection diagram.



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Fig. 19-2 State-variable band-pass filter circuit and connection diagram. Analysis 1 Compare the single-stage band-pass filter upper and lower cutoff frequencies measured in Procedures 1-5 and 1-7 with the design quantity in Example 12-7 in the text book. 2 Use the voltage levels measured in Procedures 1-6 and 1-8 to calculate the falloff rates for the single-stage band-pass filter. Compare to the theoretical falloff rate.



3

4

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From the measured quantities at the center frequency (Procedure 2-4), calculate the circuit closed loop voltage gain for the state-variable band-pass filter. Compare to the calculated gain in Example 12-11. Compare the state-variable filter center frequency and cutoff frequencies measured in Procedures 2-4 through 2-6 with the design quantity in Example 12-11 in the text book.



David A. Bell



David A. Bell

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Series Voltage Regulators Introduction Two series regulator circuits designed in examples in the text book are constructed and tested. An op-amp regulator is first tested for output voltage range, source effect, and load effect. The circuit is modified to include current limiting, and the regulator short circuit current is investigated. The second regulator circuit uses a 723 IC regulator. Tests are performed to determine its line and load regulation. Equipment DC Power Supply—(0 to ±25 V, 250 mA) Voltmeter—(0 to 25 V) Voltmeter—4½ Digital DVM Ammeter—(0 to 200 mA) Op-amp—741 (or alternative with similar specifications) IC Voltage Regulator—723 (or alternative with similar specifications) Resistors (0.25 W)—4.7 Ω, 270 Ω, 3.9 kΩ, 4.7 kΩ, 6.8 kΩ, 22 kΩ, 33 kΩ, 150 kΩ Resistors (0.5 W)—(2 × 10 Ω) Resistors (2.5 W)—60 Ω Variable Resistors (2 W)—150 Ω Potentiometer—35 kΩ Capacitors —100 pF, 100 µF BJTs—2N718, (2 × 2N3904) (or alternatives with similar specifications) Zener diode—1N757 (or alternative with similar specifications) Circuit Board

Procedure 1 Op-amp Voltage Regulator 1-1

1-2

1-3

1-4

Construct the op-amp voltage regulator circuit shown in Fig. 20-1(a) and (b), using a heat sink on transistor Q1. Note that the circuit uses the component values determined in Examples 13-2, 13-4, and 13-5 in the text book. Switch on the source voltage power supply, adjust it to 20 V, and adjust R4 to give a 12 V output (Vo). Note that a digital voltmeter that measures Vo to at least three decimal places should be used. Measure and record (on the laboratory record sheet) the voltage levels at the following points with respect to ground: Q1 base, Q2 base, D1 cathode, R4 moving contact. Adjust the R4 moving contact to its maximum point in one direction, and then in the other direction. Record the regulator output voltage in each case, then readjust R4 for Vo = 12 V.



1-5 1-6 1-7

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Adjust the source voltage to 22 V and then to 18 V. Record the output voltage change in each case, then readjust the source voltage to 20 V. Connect the 60 Ω, 2.5 W load resistor, ammeter, and switch (S1) at the regulator output, as illustrated in Fig. 20-1(c). Carefully monitoring the output voltage, briefly close S1 to switch the load resistor into the circuit then open S1 again. Record the measured output voltage change that occurred when the load resistor was connected. Also record the load current.

Fig. 20-1 Op-amp voltage regulator.

Procedure 2 Output Current Limiting 2-1

2-2

Switch off the source supply voltage and modify the circuit to include the current limiting components (Q3, R6, and R7), as illustrated in Fig. 20-2. Connect the 150 Ω adjustable load resistor (RL) in place of the 60 Ω resistor in Fig. 20-1(c). Set RL to its maximum resistance, and switch the source voltage on. Check that Vo = 12 V, and adjust R4 as necessary.



2-3 2-4 2-5

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Close S1, and slowly adjust RL until Vo commences to fall. Record Vo and IL at this point. Further adjust RL toward zero resistance so that it short-circuits the regulator output. Record the short circuit current (ISC). Open S1 once again, and check that Vo returns to its previous unloaded level.

Procedure 3 723 IC Voltage Regulator 3-1 3-2 3-3 3-4 3-5 3-6 3-7

Construct the 723 IC regulator circuit shown in Fig. 20-3. Note that the circuit uses the component values determined in Examples 13-8 in the text book. Set RL to its maximum resistance, then switch on the source voltage power supply and adjust it to 17 V. Measure and record Vo and VR2. Note that a digital voltmeter that measures Vo to at least three decimal places should be used for measuring Vo. Adjust the source voltage to 18.7 V and then to 15.3 V. Record the output voltage change in each case, then readjust the source voltage to 17 V. Close S1, and slowly adjust RL until Vo commences to fall. Record Vo and IL at this point. Further adjust RL toward zero resistance so that it short-circuits the regulator output. Record the short circuit current (ISC). Open S1 once again, and check that Vo returns to its previous unloaded level.

Fig. 20-2 Current limiting test circuit.



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Fig. 20-3 723 IC Regulator. Analysis 1 2 3 4

Compare the op-amp regulator voltage levels measured in Procedures 1-3 and 1-4 with the design quantities in Examples 13-2, 13-4, and 13-5 in the text book. Using the voltage levels measured in Procedures 1-5 and 1-7, calculate the regulator source effect, load effect, line regulation, and load regulation. Compare the short circuit current measured in Procedure 2 to the design quantity in Example 13-6. Compare the 723 regulator voltage levels measured in Procedure 3-3 to the design quantities in Example 13-6 in the text book.



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Using the voltage levels measured in Procedures 3-4 and 3-6, calculate the regulator source effect, load effect, line regulation, and load regulation.



David A. Bell



David A. Bell

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Power Amplifier Introduction A BJT output class AB power amplifier with an op-amp driver is constructed and tested for dc and ac performance. The dc voltage levels throughout the circuit are first checked without the load resistor connected. The load resistor is connected, an ac input signal is applied, and the amplifier waveforms, frequency response, output power, and efficiency are investigated. Equipment DC Power Supply—(±17 V, 200 mA) DC Voltmeter—(0 to 50 V) Two DC Ammeters (0 to 200 mA) Oscilloscope Audio Range Signal Generator BJTs—2N718, 2N722 (or alternatives with similar specifications) Heat sinks for BJTs Diodes—(2 × 1N914) Op-amp—LF356 (or alternative with similar specifications) Resistors (0.25 W)— (2 × 8.2 Ω), 470 Ω, (4 × 1.5 kΩ), (2 × 10 kΩ), 82 kΩ, Resistors (2 W)—100 Ω Capacitors —330 pF, 3.3 µF, 6.8 µF, (2 × 100 µF) Circuit Board

Procedure 1 DC Conditions 1-1 1-2 1-3 1-4 1-5

Construct the amplifier circuit shown in Fig. 21-1, using a heat sinks on both BJTs. Leave the signal generator and load resistor (RL) unconnected at this time. Switch on the power supply and adjust it for VCC = ±17 V. Use the oscilloscope to check that the circuit is not oscillating. Measure and record the dc voltage levels through the circuit as listed on the laboratory record sheet. Connect the 100 Ω load resistor and check that the dc output voltage remains zero.

Procedure 2 AC Measurements 2-1 Connect the signal generator to the amplifier input, and the oscilloscope to monitor the input and output waveforms. Connect ammeters to measure the power supply (dc) currents.



2-2 2-3 2-4

2-5 2-6

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Set the signal generator frequency to 3 kHz, and adjust the signal amplitude to produce the largest undistorted amplifier output waveform. Sketch the input and output waveforms on the laboratory record sheet, and record the peak voltages. Also record the dc supply currents. Adjust the signal frequency in steps as listed on the laboratory record sheet, taking care to keep the signal amplitude constant. Record the output voltage amplitude at each signal frequency. Change capacitor C2 to 1 µF, and investigate the new low cutoff frequency (f1). Connect a 330 pF capacitor in parallel with R3, and investigate the new high cutoff frequency (f2).



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Fig. 21-1 Op-amp/BJT power amplifier.

Analysis 1

Analyze the circuit to determine the dc voltage levels throughout the circuit, and compare to the voltages measured for Procedures 1-4.



2

3

4

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From the results of Procedure 2-3 calculate the closed-loop gain, dc input power, ac output power, and circuit efficiency. Analyze the circuit to determine these quantities, and compare to the result obtained from the measurements. From the results of Procedure 2-4 plot the amplifier frequency response, and estimate the upper and lower cutoff frequencies(f1 and f2). Calculate f1 from the circuit component values, and compare it to the experimentally determined f1. Comment on the measured f2. Calculate the new low and high cutoff frequencies for the changes made in Procedures 2-5 and 2-6. Compare the calculated and measured quantities.



David A. Bell



David A. Bell


349 28 Lab-manual Lab-manual Op Amp 3e LabManual

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