UNIVERSITY OF CALIFORNIA AT BERKELEY College of Engineering Department of Electrical Engineering and Computer Sciences EE105 Lab Experiments Prelab 10 Differential Amplifiers Name Lab Section For this lab assume all NPN transistors are identical 2N3904 BJTs and all PNP transistors are identical 2N3906 BJTs Component 2N3904 NPN BJT 2N3906 PNP BJT IS A 6 734 10 15 1 41 10 15 VA V 74 03 18 7 Table 1 Transistor properties A differential pair with a resistive load is shown in Figure 1 Use this circuit to answer the following questions You can ignore base currents Use the device parameters given in Table 1 Assume VCC 9 V Assume that the inputs are biased at 0 V DC VCC R2 R3 vout R1 vin Q3 Q1 Q4 vin Q2 VCC Figure 1 Differential pair with resistive load 1 What value of R1 would give IC1 2 mA R1 1 2 2 In lab we have 500 1 k 5 1 k and 10 k resistors Assuming we only wanted to use one resistor for R1 which value would give us IC1 closest to 2 mA What current would we get with the resistor you chose Use this value for R1 for the remainder of the prelab R1 IC1 3 We d like to bias the output half way between 0 V and 9 V to achieve the maximum swing by picking R2 and R3 appropriately Calculate a value for R2 and R3 that achieves an output bias of 4 5 V assuming R1 is what you chose for the previous question Out of the resistors listed previously which should we use What output bias does it achieve Use this value of the available resistors for R2 and R3 for the remainder of the prelab Exact R2 R3 Available R2 R3 Vout DC 4 What is the output resistance of the circuit be sure to include ro of the BJTs Assume R2 and R3 are as you chose them in the previous question of the available resistors Rout 5 What is the differential mode gain of the circuit ADM 6 What is the common mode gain of the circuit 3 ACM 7 What is the common mode rejection ratio of the circuit Use CM RR equation CM RR ADM ACM rather than the book s
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