2. Given the circuit of the 741 operational amplifier (5 points) 0n 3 279 0: O10

Question

2. Given the circuit of the 741 operational amplifier (5 points) 0n 3 279 0: O10 0s Input stage Second stage Output sage a. What is the function of Q1 and 02? Justify your answer with a sentence. b. What is the function of Q8 and Q9? Justify your answer with a sentence. What is the function of Q5, Q6 and Q7? Justify your answer with a sentence. c. d. What is the function of Q11, R5, and 12? Justify your answer with a sentence. What is the function of Q12, 013, Q14, 13, Q15, and Q16? Justify your answer with a sentence e. f. What is the function of Q17 and Q18? Justify your answer with a sentence

Explanation / Answer

a.Q1 and Q2 are the first stage consisting of matched NPN emitter followed pair which provides high input impedance.

b.Q8 and Q9 represent current mirrors. The summed quiescent currents from Q1/Q3 plus Q2/Q4 is mirrored from Q8 into Q9 where it is summed with collector current in Q10 and the result is fed to bases of Q3/Q4.

c.In case of transistors Q5,Q6, and Q7 the transistor Q7 drives Q5 and Q6 into conduction until their collector current =Q1/Q3 and Q2/Q4.

d.The resistor R5 connecting with Q11 determines the current in the current mirrors while I2 is used to supply current in case of any mismatch between predefined value and supply determined by Q11.

e.The quiescent current in Q16 is set by current mirrors Q12/Q13. I3 at Q15 gives rise to current in Q19 and the output of Q14 is a emitter follower circuit where voltage gain does not occur.

f.Transistors Q17 and Q18 provide current limiting in order to protect the amplifier from flow of heavy currents.

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