UNIVERSITY OF CALIFORNIA AT BERKELEYCollege of EngineeringDepartment of Electrical Engineering and Computer SciencesEE105 Lab Exp er imentsPrelab 10: Differential AmplifiersName:Lab Section:For this lab, assume all NPN tr ansistors are identical 2N3904 BJTs and all PNP transistors are identical2N3906 BJTs.Component IS(A) VA(V)2N3904 NPN BJT 6.734 × 10−1574.032N3906 PNP BJT 1.41 × 10−1518.7Table 1: Transistor propertiesA differential pair with a resistive load is shown in Figure 1. Use this circuit to answer the followingquestions. You can ignore base currents. Use the device parameters given in Table 1. Assume VCC= 9 V.Assume that the inputs ar e biased at 0 V DC.−VCCVCCQ1R1Q2Q3R2Q4R3vin+vin−+ vout−Figure 1: Differential pair with resistive load1. What value of R1would give IC1= 2 mA?R1=122. In lab, we have 500 Ω, 1 kΩ, 5.1 kΩ, and 10 kΩ resistors. Assuming we only wanted to use one resistorfor R1, which va lue would give us IC1closest to 2 mA? What current would we get with the resistoryou chose? Use this value for R1for 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 pickingR2and R3appropriately. Calculate a value for R2and R3that achieves an output bias of 4.5 V (as-suming R1is what you chose for the previous question). Out of the resistors listed previously, whichshould we use? What output bias does it achieve? Use this value (of the available resistors) fo r R2and R3for the remainder of the prelab.(Exact)R2= R3=(Available) R2= R3=Vout,DC=4. What is the output resistance o f the circuit (be sure to include roof the BJTs)? Assume R2and R3are 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?3ACM=7. What is the common-mode rejection ratio of the circuit? Use CM RR =ADMACMrather than the book’sequation.CM RR
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