Electronics 2 Lab Manual

TECHNOLOGICAL INSTITUTE OF THE PHILIPPINES Manila

LABORATORY MANUAL IN

ELECTRONIC CIRCUIT ANALYSIS AND DESIGN

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TABLE OF CONTENTS

Title

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Table of Contents

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Experiment No. 1

SMALL-SIGNAL ANALYSIS OF COMMON-BASE AND COMMON-EMITTER AMPLIFIERS …………

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FREQUENCY RESPONSE OF COMMON-BASE AND COMMON-EMITTER AMPLIFIERS…………………

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CASCADED AMPLIFIERS: DIRECT COUPLING AND RC-COUPLING………………………………………..

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Experiment No. 4

DIFFERENTIAL AMPLIFIER ……………………….

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Experiment No. 5

INVERTING AND NON-INVERTING OPERATIONAL AMPLIFIER…………………………………..………..

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OPERATIONAL AMPLIFIER APPLICATIONS: INTEGRATOR, DIFFERENTIATOR AND ACTIVE FILTER……………………………..…………………..

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Experiment No. 7

SINGLE-ENDED POWER AMPLIFIER ……………

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Experiment No. 8

SERIES AND SHUNT FEEDBACK CIRCUITS……

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Experiment No. 9

INTRODUCTION TO DIGITAL CIRCUITS: ELECTRICAL CHARACTERISTICS OF LOGIC GATES…………………………………………

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Experiment No. 2 Experiment No. 3

Experiment No. 6

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Experiment No.1 SMALL-SIGNAL ANALYSIS OF COMMON-BASE AND COMMON-EMITTER AMPLIFIERS 1. Objective(s): The activity aims to introduce qualitatively the common base and common emitter amplifier configuration in relationship to the voltage current and power amplification. This will also introduce the student to the concept of Rin and Rout and its effect to the amplifier circuit. 2. Intended Learning Outcomes (ILOs): The students shall be able to: 2.1 Explain the concept of small-signal analysis. 2.2 Verify the practical operations of common-base and common-emitter amplifier configurations with their theoretical operations. 2.3 Differentiate the small-signal characteristics of the two amplifier configurations. 2.4 Analyze the factors that affects the gain of the amplifiers 3. Discussion: Electrical signals that are generated by the devices are generally of small entity and therefore cannot be used practically. So as to make the small signal usable, amplifiers are used, which is able to give greater than one ratio between the signal produced at the output and the one applied in input. The process is called Amplification – the manipulation of signal to increase the amplitude (voltage, current or power) without altering other properties of the signal. Maintaining the signal shape is an essential condition since, in analog field, the information contained in the signal is associated to the shape.

Figure 1.1

Figure 1.2

Figure 1.1 shows the general terminal characteristic of an amplifier: 1. Two (2) input terminals to which the signal to be amplified is applied; 2. Two (2) output terminals where the amplified signal is taken; 3. Two (2) terminals to put power on. Figure 1.2 shows a simple external schematic diagram of a BJT amplifier (most commonly used amplifier). BJT amplifier can be used in three configurations: common-base, common-emitter and commoncollector (emitter-follower). They have common and distinct characteristics in acting as an amplifier, especially in producing the output signal and affecting its gain.

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4. Resources: Equipment: DL Console and DL3155E14 Module Oscilloscope Signal Generator Two (2) Digital Multimeters 5. Procedure: COMMON-BASE CONFIGURATION A. Transistor Amplifier Regions of Operation 1. Insert the Module DL 3155E14 in the console and set the main switch to ON; 2. Connect the circuit as shown in Figure 1.3.

Figure 1.3 3. Fill out Table 1.1 by measuring the terminal voltages (V B, VE, VC) and computing for IE. Calculate the same parameters using DC analysis considering that the V BE = 0.6V. Compare the measured and computed values. VB

VE

VC Measured Values Calculated Values

Table 1.1 4. Fill out Table 1.2 by measuring the specified voltages and calculating for I B and DC gains. 5. Verify that transistor V1 operates in the active region.

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VBE

VBC

VCE

VR1

VR2

IB (mA)

Measured Values

Computed Values

Table 1.2 6. Remove the cover of the Modifications/Faults simulator and set the first dip-switch M 1 to ON position (covered dot). Fill out Table 1.3 and determine what region of operation the transistor works. Set the dip-switch M1 to the initial upwards position. Do the same for dip-switch M 2 and M3 one at a time and tabulate the results. DIP Switches M1 M2 M3

VC

Voltages VB

VE

Region of Operation

Table 1.3 B. Small Signal Analysis 1. Connect the circuit as shown in Figure 1.4 without the load R 6.

Figure 1.4

2. Adjust the oscilloscope in the following settings: Ch1: 50 mV/DIV Ch2: 5 V/DIV Time/DIV: 100 ms Coupling: AC Signal Generator: Sinusoidal, 100 mV peak-to-peak, 10kHz 5

3. What is the phase relationship between the input and the output signal? 4. Measure the peak-to-peak output voltage and compute for the signal gain. Repeat the measurement with R6 connected and fill out Table 1.4. VS (Vp-p)

VO (Vp-p) w/0 R6

AV w/0 R6

VO (Vp-p) w/ R6

AV w/ R6

Measured Values

Table 1.4 5. Set the frequency to 1 kHz of the input sinusoidal signal with amplitude 100mV p-p unchanged. 6. Measure the voltage at R3. Calculate the circuit input current by dividing the measured resistor voltage by R3. 7. Measure the voltage at R5 and divide this value by the previously calculated current to obtain the input resistance Rin. Write the measured value in Table 1.5. 8. Calculate Rin and AV using DC analysis (use formula below) with write the result in the same table. (Note: 2N2219A at IC=1mA, f=1kHz gives hfe=100 hie=5.1kΩ)

9. Compare AV with the measured value in Table 1.4. Measure d

Rin Calculate d

AV Calculate d

Rout Calculate Measured d

Table 1.5 10. Calculate (measured value) the output resistance R out with the relationship:

11. Calculate Rout(calculated value) using the formula below and compare the results.

COMMON-EMITTER CONFIGURATION A. Transistor Amplifier Regions of Operation 1. Repeat the procedure done in common-base configuration but this time using the common-emitter circuit. Follow Figure 1.5 and fill out the necessary data needed per table.

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Figure 1.5 VB

VE

VC Measured Values Calculated Values

Table 1.6 VBE

VBC

VCE

VR1

VR2

IB (mA) Computed Values

Measured Values

Table 1.7 DIP Switches M1 M2 M3

VC

Voltages VB

VE

Region of Operation

Table 1.8 B. Small Signal Analysis 1. Connect the circuit as shown in Figure 1.4 without the load R 6.

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Figure 1.6 2. Adjust the oscilloscope in the following setting: Ch1: 500 mV/DIV Ch2: 5 V/DIV Time/DIV: 100 ms Coupling: AC Signal Generator: Sinusoidal, 1V peak-to-peak, 10kHz 3. What is the phase relationship between the input and the output signal? 4. Measure the peak-to-peak output voltage and compute for the signal gain. Repeat the measurement with R6 connected and fill out Table 1.9. VS (Vp-p)

VO (Vp-p) w/0 R6

AV w/0 R6

VO (Vp-p) w/ R6

AV w/ R6

Measured Values

Table 1.9 5. Set the frequency to 1 kHz of the input sinusoidal signal with amplitude 100mV p-p unchanged. 6. Measure the input current, output current and current gain. Compute for the input power (V S x Ii), output power (VO x IO), and power gain (PO/Pi). Record them in Table 1.10. Ii

IO

Measured Values

Ai

Pi

PO

Ap

Calculated Values

Table 1.10

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Ap (dB)

7. Measure the voltage at R2 and divide this value by the previously calculated current to obtain the input resistance Rin. Write the measured value in Table 1.11. 8. Calculate Rin and AV using DC analysis (use formula below) with write the result in the same table. (Note: 2N2219A at IC=1mA, f=1kHz gives hfe=100 hie=5.1kΩ)

9. Compare AV with the measured value in Table 1.9. Measure d

Rin Calculate d

AV Calculate d

Rout Calculate Measured d

Table 1.11 10. Calculate (measured value) the output resistance R out with the relationship:

11. Calculate Rout(calculated value) using the formula below and compare the results.

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Course: Group No.: Group Members:

Experiment No.: Section: Date Performed: Date Submitted: Instructor:

6. Data and Results:

7. Conclusion:

8. Questions and Problems: 1. In your own understanding, explain what the following terms: a. Amplification b. Small-signal analysis. c. Gain ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 2. Why is it necessary to maintain the input signal level at a constant level? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 3. How is Ai related to β? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________

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4. Determine what kind of configuration can the following circuit be classified and calculate for its gain.

9. Assessment (Rubric for Laboratory Performance):

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Experiment No.2 FREQUENCY RESPONSE OF COMMON-BASE AND COMMON-EMITTER AMPLIFIERS 1. Objective(s): The activity aims to introduce the concept of frequency response of common-base and common-emitter amplifier configurations. This introduces the students to how gain is affected by frequency variation and how to characterize their relationship using graphical method. This should also put importance on determining the proper cut-off frequencies. 2. Intended Learning Outcomes (ILOs): The students shall be able to: 2.1 Characterize how frequency affects the gain of an amplifier. 2.2 Determine how capacitance affects the frequency response of an amplifier. 2.3 Determine the lower and upper cut-off frequencies of an amplifier. 2.4 Sketch the bode plot of a corresponding amplifier frequency response. 3. Discussion: Frequency response is the quantitative measure of magnitude and phase of the output as a function of frequency, in comparison to the input. A Bode plot is a graph of the magnitude (in dB) or phase of the transfer function versus frequency. The advantage of this approach is the insight it provides on how the circuit elements influence the frequency response. This is especially important in the design of frequency-selective circuits.

Figure 2.1

Figure 2.2

Typically in electronic systems such as filters and communication channels, cutoff frequency applies to an edge in a lowpass, highpass, bandpass, or band-stop characteristic – a frequency characterizing a boundary between a passband and a stopband. It is sometimes taken to be the point in the filter response where a transition band and passband meet, for example as defined by a 3 dB corner, a frequency for which the output of the circuit is −3 dB of the nominal passband value. 12

Two applications of frequency response analysis are related but have different objectives. For an audio system, the objective may be to reproduce the input signal with no distortion. That would require a uniform (flat) magnitude of response up to the bandwidth limitation of the system. In contrast, for a feedback apparatus used to control a dynamical system, the objective is to give the closed-loop system improved response as compared to the uncompensated system. 4. Resources: Equipment: DL Console and DL3155E14 Module Oscilloscope Signal Generator Two (2) Digital Multimeters 5. Procedure: COMMON-BASE CONFIGURATION 1. Insert the Module DL 3155E14 in the console and set the main switch to ON; 2. Connect the circuit as shown in Figure 2.1 with the load R 6.

Figure 2.1 3. Adjust the oscilloscope to the following settings: Ch1: 50 mV/DIV Ch2: 5 V/DIV Time/DIV: 100 ms Coupling: AC Signal Generator: Sinusoidal, 100 mV peak-to-peak, 10kHz 4. Vary the supply frequency. Determine the lower and upper cut-off frequency in correspondence of an attenuation of the output voltage equal to 0.707 times the value to 10 kHz. Record the values. 5. Calculate the lower cut-off frequency using the following formula and fill out Table 2.1. 13

fL Measured Value

fH Calculated Value

Measured Value

Table 2.1 6. Continue to vary the frequency with a wider range this time going beyond the lower- and uppercutoff frequencies. Determine the frequency where the output voltage drops to the same value with the input voltage at both sides (low frequency and high frequency), or at least close to the input voltage. These will serve as the extreme lower and upper limit of frequency response of the amplifier. Aside from the two (2) determined extreme frequencies, create more samples of frequency to make a total of ten (10) samples including the extremes. Fill out Table 2.2 and plot the values in Figure 2.2 Frequenci es VO Gain Gain (dB)

Table 2.2

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Figure 2.2 COMMON-EMITTER CONFIGURATION 1. Insert the Module DL 3155E14 in the console and set the main switch to ON; 2. Connect the circuit as shown in Figure 2.3 with the load R 6.

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Figure 2.3 3. Adjust the oscilloscope to the following settings: Ch1: 500 mV/DIV Ch2: 5 V/DIV Time/DIV: 100 ms Coupling: AC Signal Generator: Sinusoidal, 1V peak-to-peak, 10kHz 4. Vary the supply frequency. Determine the lower and upper cut-off frequency in correspondence of an attenuation of the output voltage equal to 0.707 times the value to 10 kHz. Record the values. 5. Calculate the lower cut-off frequency using the following formula and fill out Table 2.3.

fL Measured Value

fH Calculated Value

Measured Value

Table 2.3 6. Continue to vary the frequency with a wider range this time going beyond the lower- and uppercutoff frequencies. Determine the frequency where the output voltage drops to the same value with the input voltage at both sides (low frequency and high frequency), or at least close to the input voltage. These will serve as the extreme lower and upper limit of frequency response of the amplifier. Aside from the two (2) determined extreme frequencies, create more samples of frequency to make a total of ten (10) samples including the extremes. Fill out Table 2.4 and plot the 16

values in Figure 2.3 Frequenci es VO Gain Gain (dB)

Table 2.4

Figure 2.3

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7. Conclusion:

8. Questions and Problems: 1. How does frequency relate to the gain of an amplifier? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 2. What is the importance of knowing the frequency response of an amplifier? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________

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3. What is the basis in getting the cut-off frequency at 0.707 times the value of the maximum output value? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 4. Why is it necessary to maintain the input signal at constant level? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 9. Assessment (Rubric for Laboratory Performance): Experiment No.3 CASCADED AMPLIFIERS: DIRECT COUPLING AND RC-COUPLING 1. Objective(s): The activity aims to introduce the concept of coupling or connecting circuit’s input and output with another circuit network through different methods. This shall introduce students to the DC and AC characteristics and operations of direct of DC coupling and RC coupling. This experiment shall also give knowledge to the students regarding the frequency response of the two coupling methods. 2. Intended Learning Outcomes (ILOs): The students shall be able to: 2.1 Demonstrate the operation of a two-stage RC coupled and direct-coupled amplifier by using measured circuit conditions (DC and AC operations) 2.2 Determine the frequency response of an RC coupled and direct-coupled amplifier by using measured values 3. Discussion: The frequency of the applied signal can have a pronounced effect on the response of a singlestage or multistage network. An increase in the number of stages of a cascaded system will also limit both the high- and low-frequency responses. They are amplifiers not presenting coupling capacity or transformer coupling; their frequency response extends from zero frequency (direct current) until an upper limit determined by the amplifier characteristics and they are therefore used when we have to keep the direct component of the signal, or when the signal slowly varies in time. For the RC-coupled amplifier, the drop at low frequencies is due to the increasing reactance of CC, Cs, or CE, while its upper frequency limit is determined by either the parasitic capacitive elements of the network and frequency dependence of the gain of the active device. For the direct-coupled amplifier, there are no coupling or bypass capacitors to cause a drop in gain at low frequencies. 19

Frequency Response of an RC-coupled Amplifier

Frequency Response of a Direct-coupled Amplifier 4. Resources: Equipment: DL Console and DL3155E14 Module Oscilloscope Signal Generator Two (2) Digital Multimeters 5. Procedure: A.1 DIRECT COUPLED AMPLIFIERS: DC OPERATION 1. Insert the Module DL 3155E14 in the console and set the main switch ON. 2. Connect the circuit as shown below:

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Figure 3.1 3. Turn R1 counterclockwise (R1 + R2 = R2 = 56 kW) and read, by using a multimeter, set as dc voltmeter, the values of UB1, UE1, UC1 of the V1 transistor and UB2, UE2, UC2 of the V2 transistor and then write them in Table 4.1.

Table 4.1 4. Verify that in these conditions V1 works in the active region and V2 in saturation. 5. Turn R1 completely clockwise (R1 + R2 = 156 kW) and read, by using a multimeter, set as dc voltmeter, the values of UB1, UE1, UC1 of the V1 transistor and UB2, UE2, UC2 of the V2 transistor and then write them in Table 4.1. 6. Verify that in these conditions V1 works at the limit of the linearity region and V 2 is in cut-off; 7. Observe that in a direct coupled amplifier the dc bias of each stage is not isolated. Comment on the results. A.2 DIRECT COUPLED AMPLIFIERS: AC OPERATION 1. Connect the circuit as shown below without connecting the load R9:

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Figure 3.2 2. Adjust the oscilloscope in the following way: Ch1 = 100 mV/DIV Ch2 = 2 V/DIV Time/DIV = 250 ms Coupling = AC 3. Adjust the output of the signal generator to a sinusoidal wave of 200 mV peak-to-peak- 5 kHz at the input of the first stage. 4. Adjust R1 for 13.875 at VC1 (keep this value of R1 until the end of the exercise). 5. Measure the peak-to-peak ac output signal of the first stage V O1(pp) and write the value in Table 3.2.

Table 3.2

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Table 3.3 6. Observe this signal; it is out of phase of 180° degrees with the input signal; 7. Calculate the first stage voltage gain AV1 and write down the value in Table 3.3. 8. Observe and measure the peak-to-peak ac output signal of the second stage U O2(pp) and write down the value in Table 3.2. 9. Observe this signal; it is in phase with the input signal Ui1 but out of phase of 180° degrees of the second stage input signal UI2; 10. Calculate the second stage voltage gain AV2 and write down the value in Table 3.3. 11. Calculate the overall voltage gain A V as the ratio between the output of the second stage and the input of the first stage and write the value in Table 3.3. 12. Calculate the overall voltage gain as the product of the gains of the two stages and compare the result with the previously calculated overall gain. Comment on the results; 13. Now connect the load R9 (dotted line in Figure 3.2) and measure the output U O2 and write the value in Table 3.3. 14. Calculate the gains AV2, AV again in this new configuration and write the values in Table 3.4.

Table 3.4 15. Observe how the overall gain decreases but the signal is always in phase with the input signal (see Figure 3.3 where ch1: UI1; chA: UI2 and ch2: UO2 with the connected load R9).

Figure 3.3 16. Parallel connect to the R6 (emitter resistor of the second stage amplifier) the capacitor C 2 and observe how the voltage gain greatly increases (by-pass capacitor). 17. Observe at the oscilloscope the distortion of the output U O2 with an input signal of 200 mV peak-topeak. 18. Decrease the amplitude of the input signal to the direct coupling circuit at about 30mV pp to obtain a 23

19. 20. 21. 22. 23.

not distorted signal at the output UO2. Verify that the overall voltage gain is about 100 with the connected load R 9. Comment on the results. Remove the jumper on the emitter of V 2 and set the amplitude of the input signal at 200 mV peakto-peak. Connect the load R9 and the probes 1 and 2 of the oscilloscope at the input and output of the circuit. Measure the ac output signal for frequencies from 20 Hz to 100 kHz. Calculate the gain at each frequency and plot the frequency response in Figure 3.4.

Figure 3.4 24. Calculate the range of signal frequencies over which the gain is relatively constant (bandwidth). Comment on the results. B.1 RC-COUPLED AMPLIFIERS: DC OPERATION 1. Insert the Module DL 3155E14 in the console and set the main switch to ON. 2. Connect the circuit as shown below:

Figure 3.5 24

3. Read, by using a multimeter, set as dc voltmeter, the values of U B1, UE1, UC1 of the V1 transistor and UB2, UE2, UC2 of the V2 transistor and write them in Table 3.5 4. Observe how C2 isolates the dc bias of each stage. 5. Measure the values of the emitter currents I E1=UE1/R5 and IE2=UE2/R10 and write down the values in Table 3.6

Table 3.5

Table 3.6 6. Calculate the value of the three voltages of each transistor (U C, UE and UB), considering that the voltage UBE = 0.6V, and write the results in Table 3.5. 7. Calculate the value of the emitter currents I E1 and IE2 and write the results in Table 3.6. 8. Verify that the two transistors V1 and V2 work in the active zone. Comment on the results. B.1 RC-COUPLED AMPLIFIERS: AC OPERATION 1. Connect the circuit as shown in Figure 3.6 without connecting the resistance R 12.

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Figure 3.6 2. Adjust the oscilloscope in the following way: Ch1 = 200 mV/DIV Ch2 = 2 V/DIV Time/DIV = 50 ms Coupling = AC 3. Adjust the output of the signal generator to a sinusoidal wave of 500 mV peak-to-peak- 10 kHz at the input of the first stage. 4. Measure the peak-to-peak ac output signal of the first stage U O1(pp) and write the value in Table 3.7. 5. Observe this signal; it is out of phase of 180° degrees with the input signal. 6. Calculate the first stage voltage gain AV1 and write down the value in Table 3.8

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Table 3.7

Table 3.8 7. Observe and measure the peak-to-peak ac output signal of the second stage and write down the value in Table 3.7. 8. Observe this signal; it is in phase with the input signal U I1 but out of phase of 180° degrees of the second stage input signal UI2. 9. Calculate the second stage voltage gain AV2 and write down the value in Table 3.8. 10. Calculate the overall voltage gain A V as the ratio between the output of the second stage and the input of the first stage and write the value in Table 3.8. 11. Calculate the overall voltage gain as the product of the gains of the two stages and compare the result with the previously calculated overall gain. Comment on the results. 12. Now connect the load R12 (dotted line in Fig. 3.6) and measure the output U O2 and write the value in Table 3.7. 13. Calculate the gains AV2, AV again in this new configuration and write the values in Table 3.8.

Table 3.8 14. Observe how the overall gain decreases but the signal is always in phase with the input signal (see Figure 3.7 where ch1: Ui1; chA: Ui2 and ch2: Uo2 with the connected load R12);

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Figure 3.7 15. Parallel connect to the R10 (emitter resistor of the second stage amplifier) the capacitor C 5 and observe how the voltage gain greatly increases (by-pass capacitor). 16. Observe at the oscilloscope the distortion of the output U O2 with an input signal of 500 mV peak-topeak. 17. Decrease the amplitude of the input signal to the RC coupling circuit at about 100mV pp to obtain a not distorted signal at the output UO2. 18. Verify that the overall voltage gain is about 50 with the connected load R 12 and 100 without the load. Comment on the results. 19. Remove the jumper on the emitter of V 2 and set the amplitude of the input signal at 500 mV peakto-peak. 20. Connect the load R12 and the probes 1 and 2 of the oscilloscope at the input and output of the circuit. 21. Measure the ac output signal for frequencies from 20 Hz to 100 kHz. 22. Calculate the gain at each frequency and plot the frequency response in Figure 3.8.

Figure 3.8

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23. Calculate the range of signal frequencies over which the gain is relatively constant (bandwidth). Comment on the results.

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7. Conclusion:

8. Questions and Problems: 1. What are the three types of coupling methods? State their corresponding advantage? Explain. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 2. Three amplifiers are connected in cascade and have a gain of 200. What is the gain of each amplifier stage if the 2nd stage has a gain twice the first stage while the gain of the 3 rd stage is thrice the first stage? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 3. If an amplifier with a sine wave input has a square wave output, is its operating in a linear or nonlinear function? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________

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4. What must be the ideal reactance of a coupling capacitor? Why? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 5. What is impedance matching? How a transformer provides the proper impedance match between two amplifiers? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 9. Assessment (Rubric for Laboratory Performance):

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Experiment No.4 DIFFERENTIAL AMPLIFIER 1. Objective(s): The activity aims to introduce to the student the concept, operation and characteristics of a Differential Amplifier. This will include the DC and AC analysis of the operation of the device as well as some of its most basic configurations. Basic parameters will also be covered and how they characterize the device. 2. Intended Learning Outcomes (ILOs): The students shall be able to: 2.1 Describe the operation of a differential amplifier using ac and dc measurements 2.2 Measure single-ended and differential gain using a typical differential amplifier circuit 2.3 Measure common mode gain and rejection ratio using a typical differential amplifier circuit. 3. Discussion: A differential amplifier has two identical or matched transistor circuits sharing common-emitter impedance. The transistor pair amplifies the difference between the two base signals. The output signal can be taken from the collector of one or both transistors. As shown in the figure, both halves of the circuit have equal component values, that is RC1 = RC2, RB1 = RB2 and V1 and V2 are the same type of transistor. Emitter resistor RE is common to both V1 and V2.

A balance potentiometer is used to adjust current flow through the two halves of the circuit so that under quiescent conditions and at a given temperature the collector voltages are equal. Any unequal voltage that exists between the collectors is known as dc offset voltage. Balancing compensates for component tolerances and unequal bias currents. The differential amplifier is commonly (although not always) energized by a dual polarity power source, as indicated by the +UCC and –UCC shown in the figure. A dual polarity voltage source has equal positive and negative voltages with respect to circuit common. This is made use of in determining the forward base-emitter bias required for normal quiescent conduction, and output signal referencing to 32

ground. A dual polarity voltage source also allows one or both inputs to be at a ground reference and still maintain forward conduction with high input impedance. If one input is grounded the other input is also at ground reference because of the circuit symmetry. 4. Resources: Equipment: DL Console and DL3155E16 Module Oscilloscope Signal Generator Two (2) Digital Multimeters 5. Procedure: DC OPERATION 1. Insert the Module DL 3155E16 in the console and set the main switch to ON. 2. Connect the circuit as shown below:

Figure 4.1 3. Insert a multimeter, set as dc milliammeter, in series with R 5 and -15Vdc. 4. Measure and record in Table 5.1 the current I R5.

Table 5.1 5. Connect a multimeter, set as dc voltmeter, between the collectors of V 1 and V2. 6. Measure the voltage and adjust carefully R 4 for zero volts; 7. Verify, by measuring the voltage drops across R 3 and R6 that the above zero voltage reading indicates that the collector currents of V 1 and V2 are approximately equal. 8. Record UR3 and UR6 in Table 5.1. 33

9. Calculate the collector current of V1 (IR3) and record the result in Table 5.1. 10. Verify that the collector current of V 1 (or V2) is approximately equal to one half of the total current available (IR5) measured in step 4). AC OPERATION 1. Connect the circuit as shown in Figure 4.2.

Figure 4.2 2. Set the generator for 1 kHz and minimum output. 3. Adjust R4, using a dc voltmeter between the collectors of V 1 and V2, for a zero dc offset voltage. 4. Observe the generator output with channel 1 of the oscilloscope and adjust the input signal for 500mVp-p. 5. Observe the output signal at the collector of V 1 (UC1) with respect to ground, using channel 2 of the oscilloscope. 6. Verify that the signal at UC1 is out of phase 180° with the input signal and that V 1 uses the commonemitter configuration. 7. Move channel 2 at the collector of V 2 and observe the output signal (UC2) with respect to ground. 8. Verify that the signal at UC2 is in phase with the input signal and that V 2 uses the common-base configuration. 9. Confirm from steps 5 and 7 that the type of output operation is called single-ended output. 10. Connect channel 1 probe to UC1 of V1 and channel 2 probe to UC2 of V2. 11. Use the add-invert method (Ch1-Ch2) of the oscilloscope and observe the difference signal between the collectors of V1 and V2. 12. Verify that the above signal is larger than the single-ended output. 13. Confirm from step 11 that the type of output operation is called differential or double-ended output. 14. Adjust the input signal Ui at the V1 base for 500 mVp-p, at 10kHz sine wave; 15. Observe the output signal at the collector of V 1 (UC1) with respect to ground, using channel 2 of the oscilloscope. 16. Measure and record in Table 4.2 the result.

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Table 4.2 17. Calculate the single-ended gain of V1 from the measured values using the formula A V1 = Uo/Ui = UC1/Ui. 18. Move channel 2 of the oscilloscope to observe the output signal at the collector of V 2 (UC2) with respect to ground. 19. Measure and record in Table 4.2. 20. Calculate the single-ended gain for V2 form the measured values using the formula A V2 = Uo/Ui = UC2/Ui. 21. Verify that the single-ended gain, calculated from the measured values of V 1 and V2, are similar. 22. Calculate the single-ended gain (A V) for V1 or V2, using the formula AV = RC/RE and record the result in Table 4.2. 23. Compare the results for calculated gain in step 22 to the measured gain in both steps 17 and 20. 24. Verify that those gains are the same within component and measurement tolerances. 25. Calculate the differential gain, A Vdiff, as the sum of the gain of the balanced single-ended amplifiers V1 and V2: AVdiff = AV1 + AV2. 26. Record the value in Table 4.3. 27. Set up the oscilloscope for add invert (Ch1-Ch2) measurement of the differential voltage V diff. 28. Recheck the balance (offset) to be sure that R 4 has not been moved. 29. Connect the probes of the oscilloscope to the collectors of V 1 and V2. 30. Measure and record Vdiff in Table 4.3.

Table 4.3 31. Verify that Vdiff equals the sum of the single-ended measured values of U C1 and UC2 within component and measurement tolerances. 32. Verify also that AVdiff is equal to the sum of the single-ended gains (A V) since Vdiff is equal to the sum of the single-ended voltages (UC). 33. Connect the circuit as shown in Figure 4.3.

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Figure 4.3 34. Look closely at the figure and verify that the circuit is in common-mode configuration. 35. Connect a voltmeter to the collector of V 1 and V2 and adjust carefully R4 so that the differential output is at or as close to zero as possible. 36. Go on monitoring the differential output with the voltmeter while connecting R 1 to the V1 (and V2) base with a connecting lead (dashed line). 37. Record the result (the difference between the offset reading and the reading when R 1 is connected to the circuit) in Table 4.4. (this is the common-mode output voltage U OCM).

Table 4.4 38. Notice that by connecting R1 to the input, it has been created a voltage divider (R 1, R2) at the bases of V1 and V2. 39. Move the voltmeter leads to monitor the base voltage to ground. 40. Measure and record the result in Table 4.4 (U ICM). (differential input). 41. Calculate the dc common-mode gain, AVCM from the results and record the data in Table 4.4. 42. Verify from the calculations that the dc common-mode gain is very low. AC COMMON MODE GAIN 1. Connect the circuit as shown in Figure 4.4.

36

Figure 4.4 2. Observe the common-mode input voltage, U ICM, with channel 1 of the oscilloscope and adjust the generator for 10 Vpk-pk; 10kHz sine wave. 3. Verify that the voltage at the input (V 1 and V2 base) in this configuration is the common-mode input voltage, UICM. 4. Move channel 1 probe to the collector of V1 with channel 2 probe connected to the collector of V 2 and set up the oscilloscope for add-invert (Ch1-Ch2) measurement of the common-mode output voltage, UOCM. 5. Measure and record in Table 4.5 the common-mode output voltage, U OCM.

Table 4.5 6. Calculate the common-mode gain, AVCM, from the results and the generator input using the formula AVCM = UOCM / UICM. 7. Verify, from the calculations, that the ac common-mode gain is also very low. 8. Decrease the generator voltage to minimum and remove the connecting lead between the generator and the V1 base. 9. Remove also the connecting lead between the bases of V 1 and V2. 10. Recheck the offset voltage and set to zero if necessary. 11. Insert the connecting lead between the generator and V 1 base and, with channel 1 probe at the V 1 base, set the generator for 500 mVpk-pk at 10kHz. 12. Set up the oscilloscope for add-invert measurement of the differential output voltage, V diff. 13. Connect the probes to the collectors of V1 and V2. 14. Measure and record in Table 4.6. the differential output voltage, V diff.

37

Table 4.6 15. Calculate the differential gain (AVdiff) and record the data in Table 4.6. 16. Calculate the Common-Mode Rejection Ratio (CMRR), using the formula CMRR = A VCM / AVdiff.

38




7. Conclusion:

8. Questions and Problems: 1. Distinguish between differential and single-ended inputs. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 2. Define common-mode rejection. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 3. For a given value of differential gain, does a higher CMRR result in a higher or lower commonmode gain? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 9. Assessment (Rubric for Laboratory Performance):

Experiment No.5 INVERTING AND NON-INVERTING OPERATIONAL AMPLIFIER 39

1. Objective(s): The activity aims to introduce to the student the fundamental modalities of an operational amplifier – inverting and non-inverting. This will give students the knowledge on what is the gain characteristics of the two modalities and their respective operation. 2. Intended Learning Outcomes (ILOs): The students shall be able to: 2.1 Explain the operation modalities of an inverting O.A. 2.2 Verify that the gain of an inverting O.A. depends on the feedback loop and that it can be lower, equal or greater than one 2.3 Determine the operation modalities of a non-inverting O.A. 2.4 Verify that the gain of a non-inverting O.A. depends on the feedback loop and that it can be only greater than one 3. Discussion: The operational amplifier (A.O.) is the most important and used among the linear integrated components. It is an amplifier characterized by high gain, high input impedance, low output impedance and capacity of amplifying dc signals. The word “operational” comes from the fact that originally such a device was used in the analog calculators to carry out mathematical operations on electrical signals.

The symbol that is generally used to represent the O.A. is the one in Fig.1.1 where: U1, U2, represent the input voltages Uout represents the output voltage ±Vcc represent the supply voltages and they are needed for the bias of the circuits belonging to the integrated.. It presents a differential type input whose terminals are shown as “inverting input” (-) and “noninverting input” (+): such denominations come from the fact that a signal applied to the input (-) determines in output a signal having a bias opposite to the input one, while a signal applied to the input (+) produces in output a signal having the same polarity.

40

4. Resources: Equipment: DL Console and DL3155E19 Module Oscilloscope Signal Generator Two (2) Digital Multimeters 5. Procedure: INVERTING OPERATIONAL AMPLIFIER 1. Insert the Module DL 3155E19 in the console and set the main switch to ON. 2. Connect the signal generator and the oscilloscope as shown in Figure 5.1.

Figure 5.1 3. Set the switches S1 and S2 to OFF and adjust the oscilloscope in the following way: CH1 and CH2 = 0.2 VOLT/DIV TIME/DIV = 0.1 ms Coupling = DC 4. Without supplying the signal generator, superpose, at half of the oscilloscope screen, the line of channel 1 to the one of channel 2. 5. Supply the signal generator and adjust the output at a sinusoidal voltage of 1V peak-to-peak - 1 kHz. 6. Observe, on the oscilloscope screen, the output signal of the inverting O.A.: this signal is inverted, i.e. out of phase of 180° as to the input signal; 7. Show in Fig 5.2 the signals displayed on the oscilloscope, by drawing the input wave with a dotted line and the output wave with a continuous line;

41

Figure 5.2 8. Measure the value of the peak-to-peak output voltage and the gain, by writing the results in Table 5.1.

Table 5.1 9. Calculate the gain, write the result in Table 5.1 and compare the calculated value with the measured one. 10. Set the switch S2 to ON. 11. Adjust the amplitude of the image of channel 2 to 2 VOLTS/DIV. 12. Repeat the procedure of points 8 and 9. 13. Set the switches S1 to ON and S2 to OFF. 14. Adjust the amplitude of the image of channel 2 to 0.5 VOLT/DIV. 15. Repeat the procedure of points 8 and 9 and observe that the gain of the inverting O.A. can be made lower, equal or greater than one; NON-INVERTING OPERATIONAL AMPLIFIER 1. Connect the signal generator and the oscilloscope as shown in Figure 5.3.

42

Figure 5.3 2. Set the switches S1 and S2 to OFF. 3. Adjust the oscilloscope in the following way: CH1 and CH2 = 0.5 VOLT/DIV TIME/DIV = 0.1 ms Coupling = DC 4. Supply the signal generator and adjust the output at a sinusoidal voltage of 1V peak-to-peak - 1 kHz. 5. Observe, on the oscilloscope screen, the output signal of the non-inverting O.A.: this signal is in phase and, besides, it is wider than the input signal. 6. Show in Figure 5.4 the signals displayed on the oscilloscope, by drawing the input wave with a dotted line and the output wave with a continuous line.

Figure 5.4 7. Repeat the procedures 8 to 15 of the INVERTING OPERATIONAL AMPLIFIER experiment and 43

observe that what happens: the gain of the inverting O.A. can’t be made lower or equal to one, but only greater. 8. Remove all the connections.

Course:

Experiment No.: 44

Group No.: Group Members:

Section: Date Performed: Date Submitted: Instructor:


7. Conclusion:

8. Questions and Problems: 1. What relationship did you find between input and output phases in this experiment? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 2. What relationship did you find between R f, Ri and amplifier gain? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 3. Do the data in the tables prove the formula for both inverting and non-inverting amplifier? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 9. Assessment (Rubric for Laboratory Performance):

Experiment No.6 45

OPERATIONAL AMPLIFIER APPLICATIONS: INTEGRATOR, DIFFERENTIATOR AND ACTIVE FILTER 1. Objective(s): The activity aims to introduce to the student the most basic applications of operational amplifier – as integrator, differentiator and active filter. This experiment will give the students knowledge and skills on these applications as to how they operate and which application to use them for. 2. Intended Learning Outcomes (ILOs): The students shall be able to: 2.1 Explain the operation modalities of an integrating circuit realized with an O.A. 2.2 Explain the operation modalities of a differentiator circuit realized with an O.A. 2.3 Determine the characteristics of an active band pass filter. 2.4 Determine the relationship of corner frequencies and center frequency. 3. Discussion: The integrating circuit shown in the figure has the following features: - the signal Uin is applied to the inverting terminal by means of the resistance Ri (Ii = Uin/Ri) - the not inverting terminal is grounded - the capacitor Cf is connected between Uout and the inverting terminal

The circuit shown in the figure has the following features: - the signal Uin is applied to the inverting terminal by means of the capacitor C i - the not inverting terminal is grounded - the resistance Rf is connected between Uout and the inverting terminal:

The active filters are composed of Op Amp and of RC passive components being part of the Op Amp control circuit. They are used until frequencies of the order of MHz. They present a high input impedance and a low output impedance and for their use no inductance is necessary. For the analysis of the active 46

filters we use the model of the ideal Op Amp. 4. Resources: Equipment: DL Console and DL3155E23 Module Oscilloscope Signal Generator Two (2) Digital Multimeters 5. Procedure: OPERATIONAL AMPLIFIER AS INTEGRATOR 1. Insert the Module DL 3155E23 in the console and set the main switch to ON. 2. Connect the signal generator and the oscilloscope as shown in Figure 6.1.

Figure 6.1 3. Adjust the oscilloscope in the following way: Ch1: 0.5 Volt/DIV Ch2: 1 Volt/DIV Time/DIV: 0.5 ms Coupling: DC 4. Without supplying the signal generator, superpose at the half of the oscilloscope display, the line of channel 1 and the one of channel 2. 5. Supply the signal generator and adjust the output of the attenuator with a square wave signal of 1V peak-to-peak 1 kHz. 6. Observe, on the oscilloscope display, the output signal of the integrator: this signal is a triangular wave with positive slope in correspondence of the negative half-periods of the input signal; 7. Draw the output signal in Figure 6.2.

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Figure 6.2 8. Measure the value of the peak-to-peak output voltage and write the result in Table 6.1. 9. Measure the period of the output triangular wave and write the result in Table 6.1. 10. Calculate the output voltage peak-to-peak value, and, after having written it in Table 6.1 compare it with the measured value.

Table 6.1 11. Modify the signal generator with a sine wave of 1V peak-to-peak 1 kHz and observe, on the oscilloscope display, the output signal; this signal is a sine wave having peak-to-peak amplitude of about 1.5 V. 12. Decrease the input frequency until reaching a voltage at the output of the integrator having an amplitude 7V peak-to-peak and measure the frequency (breakpoint frequency). 13. Write the value of the frequency in Table 6.2.

Table 6.2 14. Calculate the breakpoint frequency and write down the value in Table 6.2. 15. Compare the calculated value with the measured one.

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OPERATIONAL AMPLIFIER AS DIFFERENTIATOR 1. Insert the Module DL 3155E23 in the console and set the main switch to ON. 2. Connect the signal generator and the oscilloscope as shown in Figure 6.3.

Figure 6.3 3. Adjust the oscilloscope in the following way:

4. 5. 6. 7.

Ch1: 50 mVolt/DIV Ch2: 1 Volt/DIV Time/DIV: 0.1 ms Coupling: DC Without supplying the signal generator, superpose at the half of the oscilloscope display, the line of channel 1 and the one of channel 2; Supply the signal generator and adjust the output of the attenuator with a triangular wave signal of 100 mV peak-to-peak 3 kHz; Observe, on the oscilloscope display, the differentiator output signal: this signal is a positive square wave when the input signal decreases and vice versa; Draw the output signal in Figure 6.4.

Figure 6.4 49

8. Measure the value of the peak-to-peak output voltage and write the result in Table 6.3. 9. Measure the period of the output square wave and write the result in Table 6.3. 10. Calculate the output voltage peak-to-peak value, and, after having written it in Table 6.3 compare it with the measured value.

Table 6.3 11. Modify the signal generator with a sine wave of 100 mV peak-to-peak 3 kHz and observe, on the oscilloscope display, the output signal; this signal is a sine wave having peak-to-peak amplitude of about 2 V. 12. Increase the input frequency until reaching a voltage at the output of the differentiator having an amplitude 7V peak-to-peak (by slightly adjusting the input voltage) and measure the frequency (breakpoint frequency). 13. Write the value of the frequency in Table 6.4.

Table 6.4 14. Calculate the breakpoint frequency and write down the value in Table 6.4. 15. Compare the calculated value with the measured one. OPERATIONAL AMPLIFIER AS FILTER 1. Insert the Module DL 3155E23 in the console and set the main switch to ON. 2. Connect the sinusoidal signal generator, set for a frequency of 10 kHz as in Figure 6.5.

50

Figure 6.5 3. Adjust the amplitude of the signal generator at 1V peak-to-peak. 4. Connect the oscilloscope probes Ch1 (sensibility 0.5V/DIV) to the input and Ch2 (sensibility 1V/DIV) to the output of the circuit and time base 100ms/DIV; 5. Adjust the generator frequency value until locating at the output U out the maximum signal, out of phase of 180° as regards the input signal, and write the value of the central frequency f 0 in Table 6.5 6. Calculate the theoretical central frequency f 0 and write down the value in Table 6.5. 7. Measure the maximum output voltage and write the value in Table 6.5.

Table 6.5 8. Calculate the static centre-band gain: A r = Uout/Uin and compare the measured value with the theoretical one, by remembering that eventual little differences have to be attributed to the component tolerance. 9. Keep the input signal Uin = 1V peak-to-peak constant and record the frequency response curve of the filter by measuring the output voltage Uout for the frequency values shown in the Table 6.6. 10. Draw the graph of the voltage Uout as a function of the frequency.

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Table 6.6 11. Record the upper cutoff frequency fH and the lower cutoff frequency fL in correspondence of the points where the voltage results reduced of 3dB i.e. equal to the 70% of the maximum pass-band value. 12. Write in Table 6.5 the values of the two cutoff frequencies (upper and lower). 13. Calculate the filter pass band (B = f H - fL) and write down the value in Table 6.5. 14. Calculate the theoretical filter pass band and write down the value in Table 6.5. Compare the calculated theoretical pass band with the measured one. 15. Calculate the quality factor (Q = f0/B) and write down the value in Table 6.5. 16. Calculate the theoretical quality factor and write down the value in Table 6.5. 17. Compare the calculated theoretical Q with the measured one. 18. Comment on the results. 19. Observe in Figure 6.6 the behaviour of the pass band filter when the frequency of the input signal varies until about 100 kHz.

52

Table 6.6

53




7. Conclusion:

8. Questions and Problems: 1. An operational amplifier configured as a practical integrator requires what electronic component(s)? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 2. What is the relationship between the input frequency and the break frequency if the output waveform of a differentiator is a pulse type waveform? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 3. What determines the response characteristic of a filter? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 4. Where does a band pass filter generate its maximum gain? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________

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9. Assessment (Rubric for Laboratory Performance): Experiment No.7 SINGLE-ENDED POWER AMPLIFIER 1. Objective(s): The activity aims to introduce to the student the concept, characteristic, operation and parameters of single-ended power amplifier which is the most fundamental type of power amplifier. 2. Intended Learning Outcomes (ILOs): The students shall be able to: 2.1 Describe the operation of a single-ended power amplifier by using ac and dc measurements 2.2 Determine the parameters that characterize the power amplifier 3. Discussion: A power amplifier is simply an amplifier with a high power output stage. The fundamental characteristic is to supply a low output resistance so that the amplifier can provide the output signal to the load, without a gain loss. Since the output stage is the final stage of the amplifier, usually it’s a matter of relatively great signals. For this reason, it is not possible to apply neither the approximations nor the models for small signals, or anyway they have to be used very carefully. On the other hand the linearity of the device remains a very important quality; the measurements of the goodness of an output stage constitute the total harmonic distortion (TDH) that it introduces, defined as: expressed in percentage % where rms (NF) is the average quadratic value of the harmonic components of the output signal except the fundamental and rms (F) is the average quadratic value of the fundamental. A high fidelity audio power amplifier presents a value of TDH lower than 1%. Another fundamental requisite, bound to the quality of the output stage, is the efficiency with which the quantity of power that necessary to the load is supplied. We can therefore define two quantities: Conversion efficiency:

where P0 is the useful power on the load and P CC is the power supplied by the direct current supply. Merit figure:

55

where P0 is the useful power on the load and P d is the power dissipated by the active device. The second quantity implies that the power dissipated in the transistor has to be as lower as possible. This requisite comes mainly from the fact that the power dissipated in the transistor makes its internal junction temperature increase and there is a maximum temperature (between 150 - 200°C for silicon devices) beyond which the transistor is destroyed. The fact of keeping high conversion efficiency allows the extension of the duration of the batteries used in the battery supplied circuits, so to allow the use of a small and cheap power supply unit, or to remedy to the need of fans. 4. Resources: Equipment: DL Console and DL3155E15 Module Oscilloscope Signal Generator Two (2) Digital Multimeters 5. Procedure: DC OPERATION 1. Insert the Module DL 3155E15 in the console and set the main switch to ON 2. Connect the circuit as shown in Figure 7.1 with the multimeter set to dc voltmeter.

Figure 7.1 3. Measure the base, collector, emitter voltages (terminals B, C and E) and the junction voltages of the transistor V1 and write the values in Table 7.1.

56

Table 7.1 4. Measure the voltage at the edges of the load R 5 and write the value in Table 7.1. 5. Verify, from the performed measures, that the collector voltage U C is about equal to the supply voltage and that the voltage at the edges of R 5 is null. 6. Comment on the results. 7. Modify the circuit as in Figure 7.2 with the multimeter set to dc ammeter and without connecting at the beginning the signal generator at the circuit input.

Figure 7.2 8. Measure the total current IT and write the value in Table 7.2.

Table 7.2 9. Keep the ammeter series connected to the power supply and connect the signal generator to the circuit input as in Figure 7.2. 10. Set to the generator output a sine wave of amplitude 1 V pp and frequency 1 kHz; 11. Observe the total current IT and write the value in Table 7.2. 12. Verify that the total current IT is not influenced by the input ac signal and that the single-ended amplifier operates in class A.

57

AC OPERATION 1. Connect now the circuit as shown in Figure 7.4 by applying at the input a sine wave of 1 V pp and of frequency 1 kHz. 2. Connect the two probes of the oscilloscope as in figure and set the two channels 1 and 2 in AC coupling with Ch1 and Ch2 (500 mV/DIV) and TIME/DIV: 500 ms. 3. Observe the output signal to the circuit and verify that there is no distortion or clipping between the input and the output due to the class A of circuit belonging (see Figure 7.3). 4. Increase the amplitude of the input signal to the circuit and verify that beyond about 2.2¸2.3 V pp the signal is distorted. 5. Set the input signal to 1 Vpp. 6. Measure the peak-to-peak values of the input and output signals and write these values in Table 7.3. 7. Convert the peak-to-peak values in rms (root main square) of U i and Uo and write these values in Table 7.3.

Figure 7.3

Figure 7.4

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Table 7.3 8. Move the two probes of the oscilloscope to the edges of R 1 (shown in dotted lines in Figure 7.3) and measure the voltage at the edges of R 1 as difference signal (CH1-CH2) (see Figure 7.5) 9. Write in Table 7.3 the value of the voltage measured at the edges of R 1. 10. Calculate the current Ii in input to the circuit by dividing the just measured value U R1 by the value of the resistance R1 and write the value in Table 7.3 11. Convert the current value Ii in rms and write the new value in Table 7.3. 12. Verify that the value of Iirms corresponds to the calculated one if we measured at first the voltage at the edges of R1 with a multimeter set to ac voltmeter and then we divided the voltage by the value of the resistance R1.

Figure 7.5 13. Comment on the results. 14. Set the probes of the oscilloscope to the input and to the output of the circuit. 15. Calculate the voltage gain AV of the circuit and write the value in Table 7.4.

Table 7.4 16. Calculate the average input power to the amplifier (Pi) to the base of V1 and write the value in Table 7.4. 17. Calculate the output power (PO) consumed by load resistor (R5) and write down the value in Table 59

7.4. 18. Calculate the power gain AP and write the value in Table 7.4. 19. Calculate the output current of the amplifier I O (current in the load R5) from voltage measurement and resistance value. 20. Write down the value of Io in Table 1.4. 21. Calculate the current gain Ai of the amplifier and write the value in Table 7.4. 22. Verify from the Table 7.4, that the power gain A P is equal to the product of the voltage gain A V and of the current gain Ai. 23. Observe that the voltage gain of a power amplifier is low while the power gain is high because the current gain is very high. 24. Comment on the results. Course: Experiment No.: Group No.: Section: Group Members: Date Performed: Date Submitted: Instructor: 6. Data and Results:

7. Conclusion:

8. Questions and Problems: 1. In a typical transistor power amplifier, how is voltage gain and power gain related? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 2. Across where is the output of a power amplifier measured? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 3. If a loudspeaker with a resistance of 4Ω is connected to the output of a single-ended power amplifier that has a voltage drop of 10V rms across it, what is the output power of the amplifier? 60

______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 9. Assessment (Rubric for Laboratory Performance):

Experiment No.8 SERIES AND SHUNT FEEDBACK CIRCUITS 1. Objective(s): The activity aims to introduce to the student the concept of series and shunt feedback circuits. This experiment will give knowledge and skills to the students about the operation, construction, configuration and characteristics. This will also give the student knowledge on how the feedback circuits affect the parameters of the whole system. 2. Intended Learning Outcomes (ILOs): The students shall be able to: 2.1 Describe the operation of a series feedback circuit by using ac and dc measurements 2.2 Describe and measure the effect of series feedback on ac gain by using a typical series feedback circuit 2.3 Describe the effect of series feedback on input and output impedance 2.4 Understand the effect of shunt negative feedback on ac gain by using a typical shunt feedback circuit 3. Discussion: A system is said to be feedback when the output signal is connected to the input, either fully (fully feedback) or in part. The block representation system is shown below when the internal amplifier A, the feedback network  and the input summing node appear.

When in the summing node the sum of the signals X(t) + bY(t) is carried out, a positive feedback occurs, while if the difference X(t) - bY(t) is performed a negative feedback occurs. Because the positive feedback is destabilizing for the system it will be used in the oscillator circuits, while in the specific case only negative situations will be used because this one produces a stabilizing effect on the operation of the 61

amplifier.

Series

Shunt

4. Resources: Equipment: DL Console and DL3155E16 Module Oscilloscope Signal Generator Two (2) Digital Multimeters 5. Procedure: SERIES FEEDBACK 1. Insert the Module DL 3155E16 in the console and set the main switch to ON. 2. Connect the circuit shown in Figure 8.1.

Figure 8.1 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Adjust the positive variable supply to +10 V dc. Adjust R3 to obtain 5.5 Vdc at the collector of V1. Connect the emitter bypass capacitor C2 (dashed line). Set the signal generator for a 10 kHz, 3 V pk-pk sine wave at the collector of V1 (Uo). Connect the Ch1 probe to display base input voltage (U b) and the Ch2 probe to display Uo at the collector of V1. Measure Ub and calculate gain (A = Uo/Ub). Record your results in Table 8.1. Remove the emitter bypass capacitor C2 by removing the cable (dashed line). Readjust the generator so that Uo = 3 Vpk-pk. Measure Ub and calculate the gain Af (Af = Uo/Ub). 62

Table 8.1

Table 8.2 13. Record your results in Table 8.2. 14. Compare Table 8.1 and 8.2 and verify that the gain has decreased. 15. Calculate and record in Table 8.3 the feedback ratio [b = R E/(RE + RCL)] using the values of R6 and R7.

Table 8.3 16. Calculate and record in Table 8.3 the gain Af = A / (1+Ab) when feedback is present in the circuit using the calculated value of A from Table 8.1 and the one of b from Table 8.3. 17. Compare the result in step 16 to the gain (Af) in Table 8.2 and verify that the measurements agree with the calculations within normal component and measurements tolerances. SHUNT FEEDBACK 1. Insert the Module DL 3155E16 in the console and set the main switch to ON. 2. Connect the circuit shown in Figure 8.2 with feedback resistor R 2 not connected at this time (dashed line). 3. Adjust the positive variable supply to +10 V dc. 4. Adjust R3 to obtain 5.5 Vdc at the collector of V1. 63

Table 8.2 5. Set the signal generator for a 10 kHz sine wave. 6. Connect the Ch1 probe to display transistor base voltage U b; [to measure the gain of an amplifier without feedback (open-loop gain), measure from the base to the output so as to remove the effect of the series input resistor R1] 7. Connect the Ch2 probe to display collector current output voltage (U o). 8. Adjust the generator so that Uo = 3 Vpk-pk. 9. Measure Ub, calculate gain (Uo/Ub) and record the results in Table 8.4.

Table 8.4 10. Connect R2 (dashed line in Figure 8.2) and readjust R 3 for 5.5 Vdc at the collector of V1. 11. Readjust the generator so that Uo = 3 Vpk-pk; [because gain with feedback now involves series input resistor R1, measurements of gain must be made from the input terminal (U i) to the output terminal (Uo)] 12. Connect the Ch1 probe to display the input terminal U i. 13. Measure Ui, calculate gain (Uo/Ui) and record the results in Table 8.5. 14. Verify that the gain of the amplifier with feedback is lower than the gain of the amplifier without feedback. 15. Calculate and record in Table 8.6 the feedback ratio [b = R i/Rf] using the values of R1 and R2 in component list. 16. Test the data by calculating and recording gain [ A f = R2 / R1 ] in Table 8.6. 17. Compare the value for measured and calculated gain with feedback and confirm that the numbers 64

agree within normal measurements and component tolerances.

Table 8.5

Table 8.6

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7. Conclusion:

8. Questions and Problems: 1. What feedback is produced when RE is put in series with the emitter of a common emitter amplifier? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 66

2. What are the main characteristics of negative feedback when it comes to gain? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 3. How do you characterize the feedback in a shunt feedback amplifier? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 4. What effect does shunt feedback have in impedances? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 9. Assessment (Rubric for Laboratory Performance): Experiment No.9 INTRODUCTION TO DIGITAL CIRCUITS: ELECTRICAL CHARACTERISTICS OF LOGIC GATES 1. Objective(s): The activity aims to introduce to the student the fundamental concept of Digital Electronics or Logic Circuits. This activity will give the students skills in measuring and determining limits of TTL logic. TTL transfer characteristics will also be covered as well as propagation delays. 2. Intended Learning Outcomes (ILOs): The students shall be able to: 2.1 Verify, through direct measurements, the limit values of the voltage and current levels guaranteeing the right operation of a TTL logic gate 2.2 Determine the transfer characteristic of a TTL logic gate TTL 2.3 Measure the mean propagation delays of the TTL logic gates TTL 3. Discussion: It’s with the development of microelectronics that an innovative growth of logic functions has occurred. The main reason of this event was the ability of technologies in the miniaturization of the integrated circuits, i.e. we assisted to the building up of more logic circuits on the same support. The electronic components composing the digital integrated circuits are the bipolar transistors or BJT (Bipolar Junction Transistor) and the unipolar transistors or MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), commonly called MOS. In the past the BJT and MOS technologies opposed each other for the different operation speeds (the highest in the BJT, and integration density (greater in the MOS thanks to its small dimensions).Nowadays, following to a constant evolution, the two technologies are always in competition in the small and medium integration scale, since the operation speeds of the MOS

67

have been increased and the BJT dimensions have been considerably reduced. At present, the most diffused logic family is the TTL (Transistor-Transistor Logic). It is a technology using suitably integrated bipolar transistors, so to obtain both combined and sequential logic functions. It is made up of two series, commercial and military, that foresee different operation temperature ranges. The basic component is the BJT that works in switching condition, between the cut-off state and the saturation or conduction one.

4. Resources: Equipment: DL Console and DL3155E20 Module Oscilloscope Signal Generator Two (2) Digital Multimeters

5. Procedure: LIMIT VALUES OF VOLTAGE AND CURRENT LEVELS 1. Insert the Module 20 in the console and set the main switch to ON. 2. Connect the circuit and the multimeters, set as voltmeters, as in Figure 9.1.

Figure 9.1

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Table 9.1 3. Detect the instrument indications (UIH, UOL) and write them in Table 9.1 4. Connect the circuit, the millivoltmeter and the milliammeter as in Figure 9.2

Figure 9.2 5. Detect the instrument indications (UOL, IOL) and write them in Table 9.2.

Table 9.2 6. By using a multimeter, set as ohmmeter, adjust the potentiometer R 5 to a resistance value equal to 5kOhm. 7. Connect the circuit, the millivoltmeter and the milliammeter as in Figure 9.3.

69

Figure 9.3

Table 9.3 8. 9. 10. 11. 12. 13. 14.

Detect the instrument indications (I IH, UOL) and write them in Table 9.3. Repeat the operations of points 6, 7 and 8 for all the values of R 5 shown in Table 9.3. Connect the circuit and the multimeters, set as voltmeters, as in Figure 9.4. Detect the instrument indications (UIL, UOH) and write them in Table 9.1. Connect the circuit, the millivoltmeter and the milliammeter as in Figure 9.5. Detect the instrument indications (UOH, IOH) and write them in Table 9.2. By using a multimeter, set as ohmmeter, adjust the potentiometer R 5 to a resistance value equal to 5kOhm. 15. Connect the circuit, the millivoltmeter and the milliammeter as in Figure 9.6. 16. Detect the instrument indications (I IL, UOH) and write them in Table 9.3.

70

Figure 9.4

Figure 9.5

Figure 9.6

71

17. Repeat the operations of points 14, 15 and 16 for all the values of R 5 shown in Table 9.3. 18. With the potentiometer R5 set to the value of 5kOhm, connect the circuit, the voltmeter and the milliammeter as shown in Figure 9.7.

Figure 9.7 19. Detect the instrument indications (I OH, UOH) and write them in Table 9.4. 20. Connect the circuit, the millivoltmeter and the milliammeter as in Figure 9.8.

Figure 9.8 21. Detect the instrument indications (I OL, UOL) and write them in Table 9.4. 22. Remove all the connections. 23. Compare the measured values of the voltages written in Tab. 3.2a with the ones specified in the data sheet. 24. Observe and comment the current sign: the positive sign shows that the current is going into the gate; the negative sign shows that the current on the contrary goes out. 25. Compare the measured values of the currents in Table 9.3 (with R 5 = 5kOhm) and in Table 9.4 with the ones specified in the data sheet. 72

26. Analyze and comment the load influence, by considering the data shown in Table 9.3. 27. Analyze and comment the data shown in Table 9.2 in the output input connection between two NOT gates. 28. Calculate the difference UOL and UIL with the data shown in Table 9.1: this difference represents the low level noise margin (UNML), i.e. the tolerance within which eventual noises received by the circuit don't alter the logic signals (Noise Margin = NM). 29. Determine the high level noise margin (U NMH). TRANSFER CHARACTERISTIC OF A TTL GATE 1. Turn completely counter clockwise the potentiometer R 3, so to obtain an input voltage equal to 0V. 2. Connect the circuit and the voltmeters as in Fig. 3.4.

Figure 9.9 UI [V] UO [V]

0

0.4

0.8

1.2

1.3

1.4

1.5

1.6

2.0

Table 9.4

Figure 9.10 73

2.4

2.8

3.2

3.6

4.0

4.5

3. Detect the instrument indications (UI, UO) and write them in Table 9.4 4. Adjust the potentiometer R3 for all the input voltage values shown in Table 9.4 and write in the same table the corresponding output voltage values. 5. Represent graphically in Figure 9.10 the transfer characteristic of the TTL gate, describing the bond between the input voltage and the output one. 6. Remove all the connections and comment the results. MEAN PROPAGATION DELAYS OF A TTL GATE 1. Connect the circuit, the signal generator and the oscilloscope as in Figure 9.11. 2. Adjust the oscilloscope in the following way: CH1 = 0.2 VOLT/DIV CH2 = 0.2 VOLT/DIV TIME/DIV = 0.2ms coupling = DC 3. Without supplying the signal generator, superpose, at half of the oscilloscope screen, the line of channel 1 to the one of channel 2. 4. Supply the signal generator and adjust the frequency to 1MHz. 5. Observe, on the oscilloscope diagram, the input (terminal 1) and outputs (terminal 12) signals (terminals 2 and 12 of N1) and draw them in Figure 9.12.

Figure 9.12 6. Determine the propagation delay of the TTL gates. 7. Remove all the connections and comment the results.

Course:

Experiment No.: 74

Group No.: Group Members:

Section: Date Performed: Date Submitted: Instructor:


7. Conclusion:

8. Questions and Problems: 1. From the data collected, how does the diode act as a logic gate? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 2. Explain the function of a logic inverter. What is its importance in electronic and electrical circuits? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 3. How can a transistor perform electronic switching? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 9. Assessment (Rubric for Laboratory Performance):

75

Electronics 2 Lab Manual

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