EXPERIMENT # 01 Maximum Power Transfer Theorem Objectives
y
To verify by measurement, that maximum power is developed in a load when the load resistance is equal to the internal resistance of the source. y To construct a graph, using u sing measured values of voltage, current and load resistance and calculated power to verify graphically Objective 1 above. a bove. Materials Required
a. b. c. d. e.
LABVOLT test bench Digital multimeter Power Supplies Resistors of various values Breadboard
Information
The maximum power transfer theorem states that when the load resistance is equal to the source's internal resistance, maximum power will be developed in the load. Since most low voltage DC power supplies have a very low internal resistance (10 ohms or less) great difficulty would result in trying to affect this condition under actual laboratory experimentation. If one were to connect a low value resistor across the terminals of a 10 volt supply, high power ratings would be required, and the resulting current would probably cause the supply's current rating to be exceeded. In this experiment, therefore, the student will simulate a higher internal resistance by purposely connecting a high value of resistance in series with the DC voltage supply's terminal. Refer to Figure 13.1 below. The terminals (a & b) will be considered as the power supply's output voltage terminals. Use a potentiometer as a variable size of load resistance. For various settings of the potentiometer representing R L, the load current and load voltage will be measured. The power dissipated by the load resistor can then be calculated. For the condition of R L = Ri, the student will verify by measurement that maximum power is developed in the load resistor. Procedure
1. Refer to Figure 13.1, select R in in equal to 1 K representing the internal resistance of the power supply used and select a 10 K potentiometer as load resistance R L. a. Using the DMM set the potentiometer pot entiometer to 500 ohms.
b. Connect the circuit of Figure 13.1. Measure the current through and the voltage across R L. Record this data in Table 13.1. c. Remove the potentiometer and set it to 1000 ohms. Return it to the circuit and again measure the current through and the voltage across R L. Record. d. Continue increasing the potentiometer resistance in 500 ohm steps until the value 10 k ohms is reached, each time measuring the current and voltage and recording same in Table 1. Be sure the applied voltage remains at the fixed value o f 10 volts after each adjustment in potentiometer pot entiometer resistance. 1. For each value of R L in Table 13.1, calculate the po wer input to the circuit using the formula: Pinput = Vinput x IL = 10 x IL, since Vinput is always a constant 10 volts. 3. For each value of R L in Table 13.1, calculate the power output (the power developed in R L) using the formula: Pout = VRL x IL. 4.
For each value of R L in Table 13.1, calculate ca lculate the circuit efficiency using the formula: % efficiency = Pout/Pin x 100.
5. On linear graph paper, plot the curve of power output vs. R L. Plot R L on the horizontal axis (independent variable). Plot power developed in R L on the vertical axis (dependent variable). Label the point on the curve representing the maximum power.
b. Connect the circuit of Figure 13.1. Measure the current through and the voltage across R L. Record this data in Table 13.1. c. Remove the potentiometer and set it to 1000 ohms. Return it to the circuit and again measure the current through and the voltage across R L. Record. d. Continue increasing the potentiometer resistance in 500 ohm steps until the value 10 k ohms is reached, each time measuring the current and voltage and recording same in Table 1. Be sure the applied voltage remains at the fixed value o f 10 volts after each adjustment in potentiometer pot entiometer resistance. 1. For each value of R L in Table 13.1, calculate the po wer input to the circuit using the formula: Pinput = Vinput x IL = 10 x IL, since Vinput is always a constant 10 volts. 3. For each value of R L in Table 13.1, calculate the power output (the power developed in R L) using the formula: Pout = VRL x IL. 4.
For each value of R L in Table 13.1, calculate ca lculate the circuit efficiency using the formula: % efficiency = Pout/Pin x 100.
5. On linear graph paper, plot the curve of power output vs. R L. Plot R L on the horizontal axis (independent variable). Plot power developed in R L on the vertical axis (dependent variable). Label the point on the curve representing the maximum power.
Table 1.1 R L ()
500 1000 1500 2000 2500 3000 3500 4000 4500 5,000 6,000 7,000 8,000 9,000 10,000
IL (mA)
VRL (V)
Pinput (mW)
Poutput (mW)
% eff.
EXPERIMENT # 02 Solving Circuits Using Mesh Currents Objectives
y
To write the mesh equations for a resistive circuit circuit
y
Prove through measurement, that the equations eq uations written in objective 1 are valid.
Materials Required
a. b. c. d. e.
LABVOLT test bench Digital multimeter Power Supplies Resistors of various values Breadboard
Information
Refer to basic mesh analysis procedure covered in the theory course of EE 200 (3 - 1) Loop A: - Vs + (IA ± IC) R 1 + (IA ± IB) R 3 = 0 Loop B: (IB - IA) R 3 + (IB ± IC) R 2 + IBR 4 = 0 Loop C:
Procedure
1.
Select resistors and record the values in table 2.1
Table 2.1: Selected resistors for the lab work Component R 1 R 2 R 3 R 4 R 5 R 6
Measured Value
PART ONE MESH CURRENT ANALYSIS
2. Using the circuit design in figure 14.1, write the loop equations for loops A and B in the boxes given below: 3. Using Cramer¶s rule/Determinants Method solve the equations in the space given below to determine the mesh/loop currents. 4.
Record the computed values of current. IA:
IB:
5. Using the computed loop currents, compute the current through each resistor (Note the direction of current in each loop with consistency). Then measure current through each resistor and confirm your calculations. Record the values in table 14.2. Table 2.2: Current through individual resistors Computed Current Measured Current
I1 I2 I3 I4
6. Using the computed currents in each resistor, apply Ohm¶s law to find computed voltage drop across each resistor. Then measure the voltage across each resistor and confirm your calculations. Record the values in table 2.3. Table 2.3: Voltage drops across individual resistors Computed Voltage Measured Voltage
V1 V2 V3 V4
EXPERIMENT # 03 Norton theorem Objectives
y
To calculate the voltage across any one of several resistors in any circuit by using Norton¶s Theorem, and verify the results by measurements. Materials Required
a. b. c. d. e.
LABVOLT test bench Digital multimeter Power Supplies Resistors of various values Breadboard
Information
Norton¶s Theorem can be used for two purposes: a. To calculate the voltage across (or current through) any component in any circuit. b. To develop a constant current equivalent circuit, which may be used to simplify the analysis of a complex circuit. The steps used for Norton¶s Theorem are listed below: Step 1 Remove the resistor (R) across which you desire to calculate the voltage. Label these terminals ³a´ and ³b´. Short these terminals together and determine the current that flows through this short. Call this short-circuit current In.
With the terminal ³opened´ and sources replaced with their internal resistances (if any), Step 2 calculate the resistance ³looking back´ from the open terminals. This resistance is R n. Step 3
The voltage you wish to calculate will be:
V
¨ R n R ¸ ¹¹ ! I n ©© ª R n R º
Where: In is from Step 1, R n is from Step 2, and R is the value of the resistor removed in Step 1. The constant current equivalent circuit is developed from the values calculated in the above steps. See Figure 16.1.
Rn is Norton's Equivalent Resistance & In is the Norton's Constant Current Source
In
Rn
R
Figure 16.1 : Nort on's Constan t Current Equivalent Circuit
Procedure R 1 = 1K
12 V
V R 2 = 10K
R 3 = 3K
F i g ur e 1 6 . 2 : F o u r E l e m e n t C i r c u it
1. 16.2. 2.
The Norton¶s Theorem will be used to find the voltage across R 3. Connect the circuit of Figure Measure the voltage across R 3 and the current through R 3. Record. VR3 =
(meas)
IR3 =
(meas)
3. To apply Norton¶s Theorem to calculate the voltage across R 3 the steps enumerated in the Information part on page 1 are to be followed. Step 1
4. Calculate (do not measure) , I repeat do not measure the short-circuit current, In, when R 3 is replaced by a short circuit: In =
(calc)
R1 = 1K
a
In
12 V
V R2 = 10K
mA
b
Figure 16 .3: One Element Shor t Circuited
5. Connect the circuit of Figure 16.3 (this is the circuit of Figure 16.2, with R 3 removed and replaced by a short circuit, the ammeter). Make sure to use a current range higher than the calculated I n above. This measurement is the ³short-circuit´ current. In =
(meas)
Step 2 R1 = 1K
a
R2 = 10K
Rn
b
Figure 16.4: Circuit fo r calculating Rn = Rth
6. Refer to Figure 16.4, which is Figure 16.2 with R3 removed and the 12 V source replaced by a short circuit (a dead voltage source). Calculate R n from Figure and record. R n =
(calc)
7. Connect the circuit of Figure 16.4. Use the DMM to measure R n. This measurement is the ³back resistance ´ = Norton resistance = R n. R n =
(meas)
Step 3
8.
Use Norton¶s Theorem (Ohm¶s Law) to calculate the voltage (VR3) across R 3 and record. V R 3
!
¨ R n R 3 ¸ © R R ¹¹ 3 º ª n
I n ©
VR3 =
(Calc)
9. Compare the measured voltage from Para 2 with the calculated voltage in Para 8 above. If they are not close, do both over again until the error is found. 10. Draw below a schematic diagram of the Norton¶s Theorem equivalent circuit and label all values.
EXPERIMENT # 10 Clipper and Clamper circuits
Objectives: y To experimentally analyze a D iode clipper circuit (series and parallel). y To experimentally analyze a D iode clamper circuit (positive and negative). Equipments/Components: Oscilloscope, Multimeter, Semiconductor diodes, Resistors and Function Generator Procedure: Part (a): Clippers circuits
Ability to clip off a portion of an in put. 1. Series Clippers: Connect the circuit shown in figure 1 , apply the AC input Vin and observe the output. Draw the output v/s input in your notebook. 2. Series clipper with +ve DC supply : Connect the circuit shown in figure 2, apply the AC input Vin and observe the output. Draw the output v/s input in your notebook. 3. Series clipper with -ve DC supply : Connect the circuit shown in figure 3, apply the AC input Vin and observe the output. Draw the output v/s input in your notebook. What is the minimum value of Vin to turn on the diode. 4. Parallel Clippers : Connect the circuit shown in figure 4, apply the AC input Vin and observe the output. Draw the output v/s input in your notebook. 5. Parallel clipper with +ve DC supply : Connect the circuit shown in figure 5, apply the AC input Vin and observe the output. Draw the output v/s input in your notebook. 6. Parallel clipper with -ve DC supply : Connect the circuit shown in figure 6, apply the AC input Vin and observe the output. Draw the output v/s input in your notebook. What is the minimum value of Vin to turn on the diode. Part (b): Clampers Circuits: C lamp a sig nal to a different DC level.
7. Negative Clamper: Connect the circuit shown in figure 7, apply the AC input Vin and observe the output. Draw the output v/s input in your notebook. 8. Positive Clampers: Connect the circuit shown in figure 8, apply the AC input Vin and observe the output. Draw the output v/s input in your notebook.
Comments and result: Write down your comments and draw t he waveforms.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
EXPERIMENT # 11 AND/OR GATES USING SEMICONDUCTOR DIODES Objective: To experimentally analyze AND/OR gates based on semiconductor diodes. Equipments/Components: Multimeter, diodes, resistors and DC power supply. Procedure: 1. Table 1 and Table 2 show the logic for a two-input AND and OR gate respectively. 2. Connect the circuit for AND gate as shown in Fig. 1 and verify Ta ble 1. Record the observations as shown in Table 3. Use 0V for logic low input and 5V for logic high input. 3. Connect the circuit for OR gate as shown in Fig. 2 and verify Table 2. Record the observations as shown in Table 4. Use 0V for logic low input and 5V for logic high input. 4. Change the value of R s from 1K to 100 and repeat Step 2 and 3. Using theory explain the results you obtain.
Sr. No. 1. 2. 3. 4.
Sr. No.
Table 1 Input A Input B 0 0 0 1 1 0 1 1 Table 3 Input A Input B (Volts) (Volts)
Output Y 0 0 0 1
Output Y (Volts)
1. 2. 3. 4.
Sr. No. 1. 2. 3. 4.
Sr. No.
Table 2 Input A Input B 0 0 0 1 1 0 1 1
Output Y 0 1 1 1
Table 4 Input A Input B (Volts) (Volts)
Output Y (Volts)
1. 2. 3. 4.
Figure 1. A two-input AND gate
Figure 2. A two-input OR gate
EXPERIMENT # 12 Zener Diode Characteristics and Application
Objective:
y y
To experimentally observe the characteristics curve of a Zener diode. To analyze the basic Zener based voltage regulator.
Equipments/Components: y Multimeter y DC supply y Resistors y Zener Diode
Lab
measurements:
1. Construct the circuit shown in figure 1.Measure and record the value of Vz and Iz for each increment of voltage Vs in Table 1. 2. Construct the circuit shown in figure 21.Measure and record the value o f Vz and Iz for each increment of voltage Vs in Table 2. 3. Draw the characteristics curve of Zener diode in forward and reverse region and calculate R z. You can observe that Vz is not exactly constant. This shall enable you to calculate the internal resistance R z of Zener diode. 4. From table 2, estimate the Zener test current IZ-Test which is the current that brings the Zener diode in breakdown region. 5. design of a loaded Zener regulator. Refer to the loaded Zener regulator circuit shown in Fig3. Let a 1k ; load be driven by Zener diode. Let us assume that the input supply Vs has a voltage fluctuation from 1.5Vz to 5Vz. The objective of this design is to provide the load with constant supply Vz even though the input voltage fluctuate from 1.5Vz to 5Vz. in order to meet this objective, it is necessary that the Zener diode works in the breakdown region when the input fluctuates between 1.5Vz to 5Vz. To achieve this objective, we have to ensure that IZ-Test flows through the Zener diode when V is between1.5Vz to 5Vz . Let IL be the load current. Therefore the current flows through R s when Vs = 1.5 VZ will be Is= IZ-Test + IL R s = 1.5Vz ± Vz Is
The value of Rs will ensure that the Zener will be in breakdo wn region when supply is 1.5Vz . It is trivial to note that Zener will be in breakdown if Vs > 1.5Vz . Change the input from 0.5Vz to 5Vz and tabulate your results as shown in table 3.
Observations:
S.No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
s
V
V z
I z
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 2.0 3.0 4.0 5.0 10.0
S.No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Tabl e 2
S.No.
1 2 3 4 5 6 7 8 9 10 11
V z
0.5 1.0 1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0
Tabl e 1
V
s
s
V V L (V)
Is (mA)
0.5 Vz 0.8 Vz 0.9 Vz 1.0 Vz 1.5 Vz 2.0 Vz 2.5 Vz 3.0 Vz 3.5 Vz 4.0 Vz 4.5 Vz Tabl e 3
I L (mA)
I z (mA)
I z
Comments and resu l t:
Write down your comments on reading obtained from table 1, 2 and 3. Why the load voltage VL doesn¶t remains constant even though the Zener diode is in breakdown region.
Figure1
Figure2
Figure 3
EXPERIMENT # 13
BJT as a Switch
E CTIV E : OBJ
y
To theoretically and experimentally analyze the use of BJT as a switch.
Equipments/Components: y Multimeter y Transistor y Resistors y LED y DC power supplies y Function generator y Oscilloscope Lab
y
y y y
Measurement:
Figure 1 shows a simple BJT switch that is used to drive an LED. Estimate the DC current gain, dc of the BJT using DMM. By forward biasing the LED, estimate the forward voltage drop, V FLED of the LED. Usually this value is between 1.5V to 3V. Suppose our design requirement is to operate the BJT as a switch such that a current of 10mA flows through the LED when the switch is ON, i.e. I C(SAT) = 10mA when the BJT is in saturation. Using (1), we can calculate the value of R C that will enable a current of 10mA to flow through the LED when the BJT is in saturation, i.e. when V CE = 0V.
V CC ! I C RC VF LE D
y
V CE
(1)
The required base current to get 10mA saturation current can be estimated using (2). I B ( S T )
!
I C ( S T )
F
d c
(2)
y
Practically it is better to keep the base current a bit high. This is called µ hard saturation¶ . Let the hard saturation current be represented by I B(SAT-HARD). For example I B(SAT-HARD) can be 2 times IB(SAT). This ensures that the base current is high enough to keep the transistor in saturation. The required value of R B to pump IB(SAT-HARD) into the base of the transistor can be calculated using (3).
V BB V E ¢
R B
!
I ¢
( SA H A R D ) ¡
(3)
y
Construct the circuit as shown in Fig. 1 with the calculated values of R C and R B. Now apply a timer input (0 and 5V level) from function generator at base and observe the blinking of LED. Also observe the input and output on oscilloscope at dual mode. We can observe that when Vin = 0V Vout = Vcc (ON State) and when Vin = 5V , Vout = 0V (OFF State).
Figure 1
EXPERIMENT # 14 BJT Emitter-Feedback Biasing. Objective: y To analyze a BJT emitter-feedback bias circuit. y Compare the Q-point stability of the emitter-feedback bias with a base-bias circuit. Equipments/Components: Multimeter, transistor, resistors and DC power supplies. Theory/Procedure: 1. Refer to the circuit shown in Fig. 1. The circuit parameters are defined as follows: Base current y I B Collector current y I C y V CE Voltage at collector w.r.t. emitter y V BE Voltage at base w.r.t. emitter y RC Collector resistance y R E Emitter resistance y R B Base resistance y V CC Collector supply
2. The basic transistor equations are given by (1) and (2), where dc is the DC current gain of the transistor. I E ! I C I B .
(1) I C !
F dc I B .
(2) 3. Calculate the saturation current, I C( SA ) of the transistor using (3). £
I C ( SA
¤
)
!
V CC RC
R E
.
(3) 4. Adjust the value of the base current such that the collector current is approximately I C( SA ) /2. Experimentally observe the value of I C and I B and estimate the value of dc using (4). Verify the value of dc from the data sheet of the transistor. ¥
F dc
!
I C
.
I B
(4) 5. We shall now set the collector current of the transistor as per our own choice. Suppose we would like to have a collector current of 4mA. The required value of I B can be calculated using (5). The value of R B can be calculated using the equation of the base-emitter loop, (6). I B
!
I C
F d c
. (5)
I B
V CC V BE
! R B
( F d c 1) R E
.
(6) 6. Adjust R B to the value obtained from (6). Experimentally verify the value of I C. Also measure V CE and verify its observed value using (7). V CE
! V CC
I C RC I E R E . (7)
7. Draw the load line of the circuit and locate the Q-point (V CE , I C) on the load line. 8. We shall now evaluate the stability of the Q-point by observing how variation of dc effects the collector current. The transistor¶s DC current gain changes due to change in the collector current. By varying R B, increase the base current so that the collector current increases to 18mA. Measure the base current and calculate dc using (4). Compare it with dc calculated in Step 4. We shall now compare these observations with the base-bias configuration (Lab. 9) in which no feedback is provided for Q-point stability. Construct a base-bias circuit such that its saturation current is 20mA. Measure dc at IC = 4mA and 18mA. Compare the variation in dc of base-bias and emitter-bias circuits. Using theory explain why emitter-feedback bias gives better stability for Q-point as compared to the base bias circuit. 9. Try to improve the Q-point stability by increasing the value of the feedback resistor, R E. Compare your results with theory.
EXPERIMENT # 07 Design and Analysis of a Common Emitter Amplifier Objective:
y
To design and experimentally analyze a common-emitter amplifier.
Equipments/Components: Multimeter, transistor (2SC828), capacitors, resistors, DC power supply, sine wave generator. Theory/Procedure: Refer to the common-emitter amplifier shown in Fig. 1. The circuit parameters are defined as follows: DC emitter current. y I E DC ) V oltage at collector w.r.t. emitter. ( y V CE ( DC ) V oltage at base w.r.t. emitter. y V BE ( DC ) V oltage at base w.r.t. grou nd. y V B V oltage at emitter w.r.t. grou nd. ( y V E DC ) C ollector resista nce, load resistance, emitter resista nce. y RC , R L , R E AC y ac , dc , DC current gain of t he tran sistor. Resistances of voltage divider network. y R1 and R2 Power supply. y V CC V oltage gain of t he amplifier. y AV ¶ AC emitter resista nce. y r e
Vo
Figure 1. Part (1) Design Specifications for the Amplifier: 1. The input impedance of the amplifier should be roughly 5K . 2. The output impedance of the amplifier should not exceed 1K . 3. The voltage gain of the amplifier should be around 100. Part(2) Design Equations: Using the following simple rules and equations, design the amplifier to meet the above requirements.
1. R 1 and R 2 should be chosen such that the requirement of Z in(AMP) is met, where Z in(AMP) is the input impedance of the amplifier,
Z IN ( AMP )
'
|| R2 || F ac r e .
! R1
(1)
2. Using (2), calculate R E such that R IN (base) >10R 2, where R IN (base) is the input impedance of the base for DC signal.
R IN (base )
!
F dc R E .
(2)
3. Calculate the value of R C to meet the requirement of the amplifier¶s output impedance. Equation (3) will give the saturation current of the transistor. The minimum saturation current should be 10mA. In case the requirement of saturation current is not met, change the appropriate circuit parameters. I C ( SA
!
)
¦
V CC RC R E
.
(3)
4. Using (4), calculate r ¶ e required for the given voltage gain.
Av
!
RC || R L '
r e
.
(4)
5. Using (5), calculate the required emitter current.
r e'
!
25mV I E
.
(5)
6. Calculate the values of R 1 and (or) R 2 using the following equations.
! I E R E .
(6)
! V BE V E .
(7)
V E V B
V B
!
R2 R1 R2
V CC .
(8)
Part (3) Experimental Analysis: 1. Draw the DC load line of the circuit and locate the Q-point ( V CE , I C) on the load line. Observe the value of I E and compare it with the value calculated using (5). Also measure V CE and verify its observed value using (9).
V CE ! V CC I C RC I E R E .
(9)
2.
Draw the r e - model of the amplifier.
3.
Using theory, estimate the range of input signal frequency for the given coupling and by-pass capacitors.
4. Apply a sinusoidal input signal having amplitude of 1mV and frequency of 8-10KHz. Measure Vo and calculate the voltage gain. Compare it with the calculated value obtained from (4). Also observe the phase shift between the input and output signals. 5. Increase the input voltage and measure the voltage gain. You will observe reduction in the gain. You will also notice reduction in gain if the frequency of the input signal is decreased. Using theory, try to explain why this happens.
EXPERIMENT # 15 Analysis of a Common Collector Amplifier OBJECTIVE:
y
To experimentally analyze a common collector amplifier.
Equipments/Components: Multimeter, transistor (2SC828), capacitors, resistors, DC power supply, sine wave generator. Theory/Procedure: Refer to the common collector amplifier shown in Fig. 1. The circuit parameters are defined as follows: DC emitter current. y I E DC ) V oltage at collector w.r.t. emitter. ( y V CE ( DC ) V oltage at base w.r.t. emitter. y V BE ( DC ) V oltage at base w.r.t. grou nd. y V B DC ) V oltage at emitter w.r.t. grou nd. ( y V E Load resistance, emitter resista nce. y R L , R E , DC current gain of t he tran sistor. AC y ac , dc Resistances of voltage divider network. y R1 and R2 DC Power supply. y V CC V oltage gain of t he amplifier. y AV ¶ AC emitter resista nce. y r e In put impedance of t he amplifier. y Z in Output impedance of t he amplifier. y Z o Output impedance of t he source. y RS
0.1Vpp, 5 Hz §
Figure 1 Circuit Equations:
V B V E
!
r e'
Z in
!
V CC .
R E
!
(3)
I E R E .
25mV I E
F ac
(4)
.
(5)
R L
R L ) r e
RS
(2)
.
'
.
|| R 2 || F ac ( R E || R L
Z o
(1)
V BE .
V E
! V CC
( R E
! R1
!
R E
!
AV
R1 R2
! V B
I E
V CE
R2
(6)
'
r e ) .
|| R E .
(7)
(8)
Step 1. Experimentally verify the DC conditions of the circuit using (1) ± (4). Step 2. Experimentally measure the voltage gain of the amplifier and verify it using (6). You will observe that AV is close to unity. Also observe that there is no phase shift between the input and the output. Step 3. Calculate the input and output impedance of the amplifier using (7) and (8). Assume a typical value of 150 for ac. It is worth noting that Z o is around 150 times less than the output impedance of the input source. Step 4. In this step we shall experimentally check the significance of Z o. Use the signal generator that has 50 output impedance. Set the generator voltage to 0.2V p. Directly connect a 470 load resistor across the signal generator and measure the voltage across the resistor using the oscilloscope. You will observe some attenuation. Verify this result using the potential divider rule. Now connect the signal source with the common collector amplifier and replace R L in Fig. 1 with the 470 load. You will observe less attenuation in this case. Use (7) and (8) to explain your results.
EXPERIMENT # 04 RC Coupled Cascade Amplifier Experiment
OBJECTIVE:
The purpose of this experiment is to demonstrate the AC operation of RC-Coupled multistage amplifier. Some Circuit Notes:
1) The transistor is a general purpose NPN transistor (C1383 / C945 / C 828), or equivalent. For pin configuration, please refer to data sheet in appendices section of course website. 2) Assume Beta = 300, VBE = 0.7V in the prelab analysis.
Prel ab: S how only calculation s in prelab. ables should be form in In lab measurement section for bot h measured and calculated values. ¨
1. Calculate the dc parameters for both stages and record them in the ³DC analysis´ table in ³calculated´ column. Show all the calculations in prelab. 2. Perform the ac analysis for both stages and record them in ³AC analysis´ table in ³Calculated´ column. Follow the given steps. This will take you step-by-step through the process. Show all the calculations.
AC Analysis: F ind AV1 , AV2 and AVT Find AV1 We need to find R c1¶ = R 3 || R L1. R L1 for the first stage is Z in for the second stage. y Find Z base for Q2. Z base = F(r e2 + R 9) y Find Zin for Q2. Zin = R 6 || R 7 || Z base You found r e1 = 26mV / IE1 in DC analysis. Use it now to find Av1. Av1 =
R c1 R 4 + r e1
Find AV2 Now find R c2¶ = R 8 || R 11.
You found r e2 = 26mV / IE2 in DC analysis. Use it now to find Av2. Av2 =
R c2 R 9+ r e2
Find AvT Gains multiply in cascaded configuration. AvT = (Av1)(AV2) Lab
Measurements
In-lab circuit measurements: 1. Measure and record the ALL dc parameters including voltages and currents in ³DC analysis´ table in ³Measured´ column´ with the signal generator disconnected from the circuit. 2. Connect the signal generator to the circuit and set the output to an appropriate value using the oscilloscope. 3. Measure and record the ALL ac parameters including voltages at each nodes and gains in ³Ac analysis´ table in ³measured´ column using t he oscilloscope. 4. Compare measured and calculated gain and find % error %Error = (Measured ± calculated) Calculated st
nd
5. Open the coupling capacitor between 1 and 2 stage and measure the AC voltage at collector of first stage. Compare this value with VO1 in ³AC analysis measured´ co lumn. 6.
Replace the coupling capacitor that you removed in (5). Make sure that the amplifier is working normally. Connect the scope to the collector of stage 2. Note that the value of ac voltage and record it. It should be the same as the value recorded in ³measured ³column´ of ³ac analysis´ table. Remove the load resistor R 11 and note the value of VO2 again.
7. Note the value of VO1 with load resistor removed from the circuit. Compare the value of VO1 with value you recorded previously with load resistor in the circuit.
Observations:
DC Analysis Tabl e:
Parameter VB1 VC1 VE1 IC1 F1 VCE1
l cCa ul ated
Measured
Ca l cul ated
Parameter VB2 VC2 VE2 IC2 F2 VC2
Measured
AC Analysis Tabl e:
Parameter
l cul ated
Ca
Measured
AV1 AV2 AVT VO1 (CC disconnected) VO2 ( without R 11) VO1 ( without R 11)
Comments and conclusions
Sketch the wave form at every node in the circuit given below. Explain any significant discrepancies. Also, answer the following questions:
y y y y y
How would you account the error found in (4). Give reasons. Explain why the table value of VC1 in ³measured´ column is lower than value found in (5). Why the ac collector voltage of stage 2 without R L found in (6) is higher than the collector voltage with R L. Does the removal of load resistor of stage 2 have an impact on the o utput of stage 1 in (7)? nd Based on your answer to question above, what is your opinion of the use of a 2 amplifier as st means of isolation the 1 stage from the load?
Figure 1 - Cascaded RC coupled Amplifier
EXPERIMENT # 05 Darlington Pair Amplifier Abstract:
Two transistors may be combined to form a configuration known as the Darlington pair that behaves like a single transistor with a current gain equivalent to the product of the current gain of the two transistors. This is especially useful where very high currents need to be controlled as in a power amplifier or power-regulator circuit. Darlington transistors are available whereby two transistors are combined in one single package but we will construct Darlington pair by using 2 BJTs in the lab. The base-emitter volt-drop is twice that of a normal transistor. OBJECTIVE:
The purpose of this experiment is to implement and observe the performance of a CE driven Darlington pair amplifier. Some Circuit Notes: 1) The transistor is a general purpose NPN transistor (C1383 / C945 / C 828 ), or equivalent. For pin diagram, refer to data sheet in the appendices section of course website.
2) Assume Beta = 300, VBE = 0.7V in the prelab analysis. Prel ab S how only calculation s in prelab. T ables should be form in In lab measurement section for bot h measured and calculated values.
y
Calculate the DC parameters (V and I ) at every node and also calculate FF and Av and note down in table 1.
Lab Measurements
In-lab circuit measurements: 1. Connect BJTs and circuit components as per Figure 1. 2. Measure and calculate all DC parameters (V and I) in the circuit and note down in table 1. 3. Apply input signal (sine wave) of peak-to-peak amplitude in the range of volts (30- 50 mV) of frequency 1kHz to 5kHz from the frequency generator. 4. Check signal at different nodes of the BJT connected with the components. 5. Determine and measure Vo and note down in table 1. 6. Verify measured and calculated Av value.
7. Compare the calculated FD = F1 F2 and measured FD from Ic / I b.
Observations: Tabl e 1:
Parameters
l cul ated
Ca
Measured
VB1 VE1 VC1 IC1 VB2 VE2 VC2 IB2 IC2 VB3 VE3 VC3 IC3 F1 F2 FD AV Comments and Resu l t: Show the observed and ca l cul ated val ue in tabl e form. Sketch the waveform at every node in the circuit. Give the reasons of any discrepancy found in results.
Figure 1
EXPERIMENT # 06 Frequency Response of CE amplifier
OBJECTIVE:
The purpose of this experiment is to observe the frequency response of a CE amplifier with two different by-pass capacitors Some Circuit Notes:
1) The transistor is a general purpose NPN transistor (C1383 / C945 / C 828 ), or equivalent. For pin diagram, refer to data sheet in the appendices section of course website. 2) Assume Beta = 300, VBE = 0.7V in the prelab analysis. Prel ab
S how all calculation s in prelab. 1) For the circuit in figure 1 , calculate the values of all DC parameter and AC gain (Avmax)of the circuit and note down in table 1. 2) Take Cs = 10 F and Cc = 1 F. We are going to observe the frequency response of CE amplifier with different CE capacitor. 3) Calculate cutoff frequencies for all capacitors with 2 different CE values. a. 100 F b. 20 F Note that f LE should be dominant frequency among the three frequencies otherwise change the value of CE to make the frequency dominant.
Lab Measurements
In-lab circuit measurements: 1. Connect the circuit of figure 1. 2. Measure all the DC parameters and not e them with calculated values in table 1. 3. For CE = 100µF: Now apply the AC signal and calculate the maximum gain of the circuit.
y
Set the frequency range at 10 kHz and rotate the frequency dial from 0 to 360 degree (a complete rotation) and observe the maximum output that is constant for a wide range of frequency. This is the maximum output of the circuit and calculates the maximum gain of the circuit (Avmax ) and note down in table 1.
4. Now start with 50Hz frequency and note the value of Vo at different frequencies (50Hz, 100Hz, 500Hz, 1kHz, 5kHz, 10kHz, 50kHz, 1Mhz) and note down in
table2. Also find the lower and higher cutoff frequencies where the output is 70.7% of Vomax. 5. Repeat the step 3 and 4 for CE = 20µF. Observation:
Parameters
l cul ated Val ues Ca
Measured Val ues
VB VE VC IC IB F VCE AVmax f LCs f LCc
-
Table 1 For CE = 100µF: For CE = 20µF: Measured Cutoff frequency: f LC E= ____ Measured Cutoff frequency: f LC E= ____ Calculated Cutoff frequency: f LC E= ____ Calculated Cutoff frequency: f LC E = ___ Frequency (Hz) 50
Vo
Av
Av(db) =20log Av
Table 2
Frequency (Hz) 50
Vo
Av
Av(db) =20log Av
Table 3
COMMENTS AND RESULTS: Draw
the graph on semi-log graph paper between frequency and Av(db) .Draw the graph for both capacitors on same graph paper and measure the bandwidth for both capacitor values. Also show the change in db per decade.
Answer the following questions:
y y y y
What are the effects of bypass capacitor values on cutoff frequencies? What is the effect of CE on bandwidth of the CE amplifier? Is higher frequency response dependent of CE? Why are we taking f LCE as a dominant frequency?
Figure 1
EXPERIMENT # 08 Differential Amplifier
Abstract:
The Differential amplifier has its greatest application in ICs. Its design is normally related to IC fabrication techniques. It consists of two transistors that have same characteristics. The output is proportional to the difference between the two input signals. In common mode DA rejects the signal whereas in differential mode it amplifies the signal. Purpose of the Ex periment
y y
The purpose of this experiment is to implement and observe the output waveforms of DA in the two modes. To find CMRR of the differential amplifier.
Some Circuit Notes: 1) The transistor is a general purpose NPN transistor (C1383 / C945 / C 828 ), or equivalent.
2) Assume Beta = 300, VBE = 0.7V, Vcc = 9V, Rc = 3.9K in the prelab analysis. Prel ab S how only calculation s in prelab. T ables should be form in In lab measurement section for bot h measured and calculated values.
Calculate the DC parameters (V and I ) where is required. Lab Measurements
In-lab circuit measurements: 8. Connect BJTs and circuit components as per Figure 1. 9. Measure and calculate all DC parameters (V and I) in the circuit and note down Apply common mode input signal (sine wave) of peak-to-peak amplitude in the range of volts (30- 50 mV) of frequency 1kHz to 5kHz from the frequency generator. 10. Observe the output waveform . 11. Determine and measure Vo and Acm and note down. 12. Now apply different input signals (sine wave) at base of Q1 and Q2 of peak-to peak amplitude in the range of volts (30- 50 mV) of frequency 1kHz to 5kHz from the frequency generator. 13. Observe the output waveform. 14. Determine and measure Vo and ADM and note down.
F ormul ae:
ACM = Vo/Vind ADM = Vo/Vind. CMRR = 20log ADM/ACM (dB) Tabl e 1: V B1 V E 1 V C1 I C1 V B2 V E 2 V C2 I B2 I C2
Parameters
l cul ated
Ca
Measured
Comments and Resu l t: Show the observed and cal cul ated val ue in tabl e form. Sketch the waveform for both modes of operation. Give the reasons of any discrepancy found in results.
EXPERIMENT # 09 Operational Amplifier Experiment Abstract:
The purpose of these experiments is to introduce the most important of all analog building blocks, the operational amplifier (³op-amp´ for short). The Lecture notes on my website gives an introduction to these amplifiers and a smattering of the various configurations that can be used in. Apart from their most common use as amplifiers (both inverting and non-inverting), they also find applications as buffers (load isolators), adders & subtractors, integrators, differentiators amplifiers, impedance converters, filters (low pass, high-pass, band-pass, band-reject or notch), and differential / instrumentation amplifiers. OBJECTIVE:
Design and implement basic operational amplifier circuits including inverting, non inverting and summer amplifier with various feedback netwo rks and examine their properties. Pre Lab:
Read out the lecture notes on op-amp circuits. Lab
Measurement:
Note: Use Dual power supply (fig 5) with Op a mp for biasing. Inverting amplifiers (Voltage - shunt feedback)
Choose Ri = 1k ;and R f= 10k ; in fig 1. Using a sine wave input o f appropriate magnitude, measure the gain of the circuit Repeat for R f = 50k ; . What is the calculated gain for each of these cases? Co mpare them. Parameter Av (R f = 10k) Av (R f = 50k)
Calculated
Measured
Non-inverting amplifier (Voltage-series feedback)
Repeat the above procedure for non-inverting amplifier (fig 2).
Parameter Av (R f = 10k) Av (R f = 50k)
Calculated
Measured
Summer Amplifier (Adders):
Set up the summing amp circuit (fig 3) with R 1 = R 2 = R i =10k and R f =20 k . Use the voltage divider to provide 2 d ifferent AC inputs with same frequency and appropriate magnitude. ( You can also do this experiment by using DC source instead of AC). Measure Vout for values of Va and V b and verify that Vout = - R f (Va + V b)/R i.. Now change the configuration by taking R 1 = 10k , R 2= 20k and R f = 20k. Supply single AC voltage (or DC) to both inputs and measure Vout. Compare both outputs with calculated values of Vout. Parameter
Calculated
Measured
Vo (R1 = R2 = Ri =10k and Rf =20k) Vo(R 1 = 10k , R 2= 20k and R f = 20k) Differential Amplifier (Subtractor):
Set up the circuit shown in fig 4 for subtracting two voltages. Use R i = R f = 10 k .. Use the voltage divider to provide 2 d ifferent AC inputs with same frequency and appropriate magnitude. ( You can also do this experiment by using DC source instead of AC). Measure Vout for values of V1 and V2 and verify that Vout = R f (V2 - V1)/R i. Parameter Vo (Rin =10k and
Calculated
Measured
Rf =10k)
Comments and Resu l ts:
Compare the calculated and measured value of gains in all 4 applications in table form.
Fig: 3 Summer Amplifier
Fig 4: Difference Amplifier
Fig 5: Dual Power supply
