Download EE_115AL_Experiment_7

EE 115AL Experiment 7
Designing a “CE”, a “CB”, & a “CC” Amplifiers
Instructor: Dr. Mesghali, Farid
TA: Mohamed, Mohamed (Section 3)
Quarter: Spring 2012
Lab Partner: Hans Christian Caliyana
Name: Kenny Lu
UID: 903801866
Introduction/Objectives
In this lab, we use our knowledge of BJT transistors and amplifier setups from from
experiment 5 and 6 to design three single stage amplifiers. We will design a CE, CC, and CB
amplifier with certain specifications. We then construct our designed circuit and test them to
see if they meet our required specifications. The voltages that we must obtain and also the gain
of the output set the specifications. To control this we change the resistances of the biasing
circuits. We all choose the capacitances, which we use to filter the inputs and outputs of our
circuit.
Results and Discussion
Part I – Common Emitter Amplifier
a) CE Amp Configuration:
Use design equations for a CE amplifier and design a single-stage CE amplifier given
certain requirements for voltage gain, input impedance, Vcc and load resistance. We
then construct the circuit and measure the DC and AC characteristics and compare them
to the desired values.
Desired values: av = -10, Ri = 1kΩ, VCC = 12V, RL = 2.2kΩ
+
12V
R1
RS
C1
C2
+
+
+
Vs1
10V
R2
RE
RL
-
Using the equations for the common emitter and Q-point learned in lab 5, we solve for
the unknowns and get the following values for our resistors.
R1 (Ω)
R2 (Ω)
RB (Ω)
RC (Ω)
RE (Ω)
RL (Ω)
11810
1189 1080.244
2185
99.1
2160
b) DC Bias
Use the DMM, and measure VB, VBE, VCE, VRE to get the DC bias of the amplifier
ICQ = VRC/RC (A) VCEQ (V) VRC (V) VB (V) VC (V)
0.00373
3.528
8.15 1.062
12
Thus we are within the range of our target of ICQ = 3.5mA and VCEQ = 4.2V
c) CE Max Output Swing
Set the frequency to 10kHz and increase the input voltage until the output voltage
becomes distorted. Note the maximum.
When the input is at 0.61 volts, the output is at 5.85 volts. Further increase of the input
voltage distorts the output. Thus 5.85 volts is the max output swing.
d) AC Voltage and Current Gain
Using the scope, measure the input signal, vin,pp, and the output signal, vout,pp. Calculate
the gain, Av = vout,pp / vin,pp. Connect in-series a test resistor to the input/input
resistance. Adjust the input such that there is 1Vpp at the output.Using the scope,
measure the peak-to-peak voltage across the test resistor. Calculate the currents, and
then the current gain, ai = - iout,pp / iin,pp.
Vipp (V) Vopp (V) Av
0.1
1.009
10.09
RT
Vinpp
Vopp
Iin-pp = vinpp/RT
Iout-pp =
(Ω)
(V)
(V)
VRT (V) (A)
voutpp/RL (A) Ai = iout-pp / iin-pp
1022
0.2
1.005
0.1008
9.86301E-05
0.000465
4.7174
e) AC Input and Output Resistance
To measure the input resistance, we add a test resistor RT close to the expected value of
Rin. We then measure the current through the test resistor. Using the measured current
and Vin, we find Rin.
Rin (Ω)
1009.87
To measure the output resistance, we use a variable resistor. First, we adjusted the input
voltage VI until the output voltage is VO. Then we add a variable resistor at the load, and
adjust its resistance until the VO‘ is equal to half the VO
Vi (V)
Vo (V)
Vo' (V)
Ro (Ω)
0.1
1.027
507
1005
f) Frequency Response
Set the input voltage such that the output voltage is 1 volts at a frequency of 10kHz.
Adjust he frequency, up and down, until vopp is equal to 0.707 times the vopp in the
previous step, to determine f-3dB,high and f-3dB,low.
f (Hz)
5
13
30
50
10026
15000
30000
100000
250000
500000
1000000
5000000
6000000
8000000
10000000
Vi (V)
Vo (V)
Av
0.6
0.6
1
0.11
0.66
6
0.108
0.9 8.333333
0.108
0.98 9.074074
0.12
1.08
9
0.12
1.07 8.916667
0.12
1.07 8.916667
0.118
1.05 8.898305
0.106
0.98 9.245283
0.108
1.06 9.814815
0.106
1.04 9.811321
0.102
0.82 8.039216
0.104
0.75 7.211538
0.098
0.62 6.326531
0.092
0.52 5.652174
Since maximum gain is around 10, the high and low 3db points are roughly 13Hz and
6MHz.
Gain VS Freq
12
Voltage Gain
10
8
6
4
2
0
0
5
10
15
20
Frequency in log scale ln(f)
Part II – Common Collector Amplifier
a) CC Amp Configuration
In this section, we follow the same procedure as in part 1 but with design equations for
a CC amplifier.
+
12V
R1
RS
C1
C2
+
+
+
Vs1
10V
R2
RE
RL
-
Thus with given desired values as ai = 10, VCC = 12V, RL = 2.2kΩ, we use the equations for
common collector to obtain:
R1 (Ω)
R2 (Ω)
RE (Ω)
RL (Ω)
32440
80440
2185
2160
b) DC Bias
Use the DMM to measure the bias voltages and verify the DC biasing condition.
VRE (V)
VCEQ (V)
ICQ = VRE/R1 (A)
7.3
4.72
0.003341
c) Max-output Swing
Using the same procedure as for common emitter amplifier, when Vinpp is 7.5 volts,
Vopp is at the max-output of 7.4 volts. Further increase in input voltage distorts the
output voltage.
d) AC Voltage and Current Gain
Apply a 10kHz sine-wave such that the vopp is 1-2Vpp. Measure the vopp and vipp.
Calculate the voltage gain.
Vipp (V) Vopp (V) Av
1.1
1.057 0.960909
Now, insert a test resistor RT after CB. Measure the voltage across the added resistor.
Then, measure vopp. Calculate the current gain.
RT (Ω) Vipp (V) Vopp (V) VRT (V) Iinpp = Vipp/RT (A) Ioutpp = Vopp/RL (A) Ai
22180
2.2
1.03
1.1
4.95942E-05
0.000477 9.615067
e) Input and Output Resistance
Using the same approach as for the common emitter amplifier, we get
Rin (Ω)
22180
Vo (V)
Vo' (V)
Ro (Ω)
0.107
0.05
9.3
f) Frequency Response
Again, set the input voltage so that the output voltage is equal to 1 volts at a frequency
of 10kHz. Then sweep the frequencies to get the high and low 3dB points.
F (Hz)
3
5
8
10
15
20
50
100
5000
10000
50000
100000
500000
1000000
5000000
9000000
11000000
Vi (V)
Vo (V)
Av
1.04
0.42 0.403846
1.06
0.56 0.528302
1.06
0.78 0.735849
1.06
0.88 0.830189
1.06
0.92 0.867925
1.06
1 0.943396
1.06
1.06
1
1.06
1.06
1
1.06
1.06
1
1.08
1.08
1
1.06
1.08 1.018868
1.06
1.06
1
1.06
1.06
1
1.08
1.08
1
1.08
1.09 1.009259
0.98
1.14 1.163265
0.9
1.14 1.266667
The low 3dB point is f = 8Hz and the high 3dB point is out of range, because the function
generator cannot reach a higher frequency. We see that there is a slight peak at the
voltage gain then the frequency goes beyond 9MHz.
Gain VS Frequency
1.4
Voltage Gain
1.2
1
0.8
0.6
0.4
0.2
0
0
5
10
Frequency in log scale ln(f)
15
20
Part III – Common Base Amplifier with Bypass Capacitor CB
a) CB Amp Configuration
In this section, we follow the same procedure as in parts 1 and 2 but with design
equations for a CB amplifier.
+
12V
R1
RC
Cc
+
RS
+
+
CB
R2
CE
RE
+
RL
-
Desired values: av = -10, Ri = 1kΩ, VCC = 12V, RL = 2.2kΩ
Using the equations for CB with bypass base capacitor, we get:
RL (Ω)
R2 (Ω)
2161
R1 (Ω)
32470
RE (Ω)
50320
Rc (Ω)
2174
2141
b) DC Bias
Using the DMM, measure the bias voltages to get the bias condition of the CB amplifier
ICQ = VRC/RC (A)
0.00170481
VCEQ (V)
4.657
VRC (V)
3.65
c) Maximum Output Swing
Reset the frequency to 10kHz. Increase the input voltage until the output voltage
becomes distorted. Note the maximum.
The maximum output swing is when Vopp = 3.87 volts.
d) AC Voltage and Current Gain
Using the same approach as for the CB and CE configurations,
vo (V)
vi (V)
1.14
vRT (V)
0.021
RT(Ω)
18.9
0.021
ii (A)
0.00111111
Av
54.2857143
vo (V)
freq (kHz)
10
vi (V)
1.14
0.041
io (A)
0.00052753
Ai
0.4747
e) Input and Output Resistances
Using the same approach again, we have,
Rin (Ω)
Rout (Ω)
18
1051
f) Frequency Response
Similarly, we sweep thought the frequencies to get to 3db points.
freq (Hz)
vo (V)
10
25
50
75
100
150
200
300
500
800
1000
5000
10000
10000
1000000
2000000
4000000
5000000
8000000
10000000
vi (V)
0.015
0.039
0.096
0.272
0.348
0.56
0.66
0.76
0.864
0.92
0.94
0.98
1
0.98
0.97
0.95
0.86
0.78
0.59
0.42
0.059
0.058
0.056
0.054
0.052
0.05
0.047
0.039
0.03
0.025
0.022
0.018
0.016
0.016
0.015
0.016
0.016
0.016
0.014
0.011
Av
0.25423729
0.67241379
1.71428571
5.03703704
6.69230769
11.2
14.0425532
19.4871795
28.8
36.8
42.7272727
54.4444444
62.5
61.25
64.6666667
59.375
53.75
48.75
42.1428571
38.1818182
Voltage Gain VS frequency
70
Voltage Gain
60
50
40
30
20
10
0
0
5
10
Frequency in log scale ln(f)
15
20
Conclusion
The CE, CC, CB amplifiers that we designed in this lab were very accurate and followed the
design requirements exactly. Also, the data gathered in each section of the experiment was very
accurate and followed the theoretical expectations. I found these experiments to be very
successful at teaching how to use design equations to choose resistor values for the three
amplifier configurations. I have learned a lot about how to design an amplifier and this lab did a
great job in complementing our knowledge of the BJT and the applications for each
configuration.