ECET 2310 (Electronics II) Laboratory Exercise 6
Differential Amplifier
In this investigation you will predict the dc and ac performance of a differential amplifier. During the lab session
you will build a differential amplifier and measure the actual performance of your circuit. You should expect
reasonable agreement between the predicted performance and the actual performance.
PROCEDURE Part A. - Preliminary Calculations:
For this part, assume that Q1 and Q2 are perfectly matched and have the following specifications: (Note: some of
these specifications may not be needed to perform the required calculations)
hFE = hfe = 500 hib = 26 mV/IE
VBE = 0.6 V hoe = 10 µS
1. Assuming that the bases of Q1 and Q2 are both grounded, determine the following predicted dc voltages and
currents for the differential amplifier circuit shown in Figure 1:
VE1 = _______ VC1 = _______ IC1 = ______
VE2 = _______ VC2 = _______ IC2 = ______
2. Determine the single-ended output difference-mode gain (relative to vo1) of the circuit shown in Figure 1.
Ad (single-ended output) = ______
3. Determine the single-ended output common-mode gain (relative to vo1) of the circuit shown in Figure 1.
Acm (single-ended output) = ______
4. Determine the CMRR dB for the circuit shown in Figure 1, utilizing the results of steps 2 & 3, Part A.
CMRR dB = ______
10 k
Ω
10 k
Ω
+15 V
V
i1
V
i2
-15 V
V
o2
V
o1
100 k
Ω
Figure 1
Q1 Q2
