ME 462 - Lab 4 - AMPLIFIER CIRCUITS
Goals
Design, build and debug operational amplifier and push-pull power driver circuits
Analytically model and experimentally verify frequency response characteristics
741/411 Operational Amplifier
Operational amplifiers (op-amps) are extremely useful analog circuit components. They can amplify DC
or AC voltages, can be used to build analog filters, can provide impedance buffering and can source/sink
increased current output compared to signal generators or TTL chips. Performance characteristics of one
of the most common op-amps used in industry and in this lab provided below.
Maximum supply voltage:  18 V
Power dissipation:
500 mW
Output voltage swing:
within 1.5 V of supply
Slew rate (typical):
0.5 V/s
fMAX (typical):
1 MHz
8 NC
OFFSET NULL 1
INVERTING INPUT 2
-
7 +V
NONINVERTING INPUT 3
+
6 OUTPUT
-V
5 OFFSET
NULL
4
Procedure
1) Build the non-inverting op-amp circuit shown in Figure 1. Refer to Figures 4.6 and 4.7 in Horowitz
and Hill and MATLAB code on the class web page to help analyze performance of this circuit. Design
the circuit to achieve the following criteria. Wherever possible, use resistors of 1K or larger.
a) R1 and R2 provide passband gain K = 100 = 1 + R2/R1
b) R3 and C2 provide standard first-order high-pass filtering with fc = 16 Hz = 1 / (2  R3 C2)
c) R1 and C1 provide unity gain at DC and passband gain above fc = 160 Hz = 1 / (2  R1 C1)
R1 = __________ R2 = __________ R3 = __________ C1 = __________ C2 = __________
+15V
+15 V
VIN
3
C2
R3
+
2
-
7
4
-15 V
6
NPN
TIP 29 or
TIP 31
SIGNAL
OUT
Q1
SIGNAL
IN
R4 = 1K
R2
R1
Q2
PNP
TIP 30 or
TIP 32
C1
-15V
Figure 1. Input amplifier circuit
Figure 2. Speaker drive circuit
2) Build the speaker drive circuit shown in Figure 2. What is the purpose of the 1K resistor in the
circuit? Why is it so large here? Power transistors are necessary in this application, since the op-amp
cannot produce enough current to drive the speaker. Note that higher power amplifier chips are
commercially available such as the LM384 which can handle up to 5 watts.
3) Connect the two circuits and test their operation by using a signal generator to provide a sine or
triangular wave as the input. Adjust the output level of the frequency generator to achieve an output of
±4.5 V peak-to-peak (p-p) at the output of the op-amp (to stay within the ±5 V range of your DAS-08
A/D). Check levels with your handheld DVM. Note that the DVM measures RMS voltage, not p-p.
What is the difference between p-p and RMS voltage measurements?
4) Leave the speaker drive attached and connect the op-amp output to the PMD 1208-FS A/D channels.
Use the digital scope software to display the signal on the screen.
5) Analytically determine frequency response of the op-amp circuit in Figure 1 including filter and slew
rate effects, and plot on the axes provided below.
40 dB
Voltage
Gain
20 dB
0 dB
1
10
100
1K
10K 100K
Frequency (Hz)
1M
10M
Based on this amplifier's published maximum slew rate, determine the maximum operating frequency for
distortion-free operation at ±4.5 V output.
___________ Hz
6) Experimentally determine and plot gains for a sine wave input at several frequencies, and plot these
results on the graph above to compare to your analytical predictions. Discuss similarities and differences
between analytical and experimental filter performance.
7) Determine the input voltage amplitude from the signal generator at which the output voltage of the
op-amp begins to clip. Use an input frequency of approximately 200 Hz. How does this compare to the
value you would predict from the nominal closed loop frequency response? Plot the clipped waveform.
8) Use a second A/D input channel and the digital scope software to look at the voltage across the
speaker while at the same time, viewing the op-amp output. Use a sine wave input to the op-amp circuit.
Compare the output of the op-amp to the speaker input. Do you see any evidence of cross-over
distortion? Plot the waveforms.
9) Demonstrate your circuits to the TA.
10) Submit these completed lab sheets including answers to all questions along with plots in lieu of a
report.
11) EXTRA CREDIT – Play a tune on your speaker using your Atom28 as input to your op-amp circuit.
Tone
C
C#
D
D#
E
F
F#
G
G#
A
A#
B
Freq (Hz) 261.6 277.2 293.7 311.1 329.6 349.2 370.0 392.0 415.3 440.0 466.2 493.9
TO-220 package
for TIP 29, 30, 31, 32
B
CE