Operational Amplifier Internal Circuit – 4 MCQ’s

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This set of Signals & Systems Multiple Choice Questions & Answers (MCQs) focuses on “Operational Amplifier Internal Circuit – 4″.

1. In Darlington pair differential amplifier the current gain is given as 100. Where IB1=5µA and IC1=0.35mA. Determine IC2
a) 0.5mA
b) 1.5mA
c) 2mA
d) 0.15mA

2. In the circuit shown, find the overall current gain?

Find the overall current gain from the given circuit diagram

a) 456218
b) 444878
c) 444210
d) 455734

3. To increase the input resistance, the differential amplifier replaces transistor by
a) Current mirror
b) Current repeater
c) Darlington pair
d) All of the mentioned

4. Introducing FET differential amplifier pair at the input stage of differential amplifier produces
a) High output resistance
b) High input resistance
c) Low input impedance
d) All of the mentioned

5. Which circuit is used as active load for an amplifier
a) Wildar Current source
b) Darlington pair
c) Current Mirror
d) All of the mentioned

6. The input voltage of a difference amplifier are 2.5v and 4.9v. If the transconductance is 0.065Ω-1, determine the load current entering the next stage
a) 0.156A
b) 1.56A
c) 0.156mA
d) 15.6µA

7. Why active load is used in amplifier to obtain large gain in intermediate stage of amplifier?
a) To obtain a very large voltage gain
b) To get High input resistance
c) To reduce the noises
d) To increase current gain

8. What is the equation of load current for a differential amplifier with an active load?
a) IL = gm×vd
b) IL = Iq /2
c) IL = β×Iq×( Vin1 – Vin2)
d) IL = 2×gm/( Vin1 – Vin2)

9. Calculate the VI – VO for the level shifter shown in the figure (Assume identical silicon transistor and very large value of β). Transistor QA and QB form current mirror.

Calculate the VI–VO for the level shifter by assuming identical silicon transistor and β value

a) 5.56V
b) 6.00v
c) 7.98v
d) 6.65v

10. What is the need for level shifter in operational amplifier?
a) Level the quiescent voltage
b) Remove distortion at output
c) Limits the output voltage
d) Increase the quiescent voltage

11. An output stage amplifier can produce output signal, when the input signal is
a) 0.48v
b) 0.9v
c) 1.2v
d) 0.5v

12. Load resistors (Re) is neglected for maximizing the voltage gain in amplifier because,
a) Requires large chip are
b) Requires large power supply
c) Quiescent drop across Re increases
d) All of the mentioned

13. Limitation of an output stage amplifier, if it emitter follower with complementary transistor
a) Cross-over distortion
b) Low impedance output
c) Shift in level
d) Active load current

14. Find the disadvantage in the following circuit diagram:

Find the disadvantage present in the given circuit diagram

a) Voltage get attenuated by R1
b) Voltage get attenuated by R2
c) Voltage get attenuated by R1 and R2
d) Voltage shift get increased by the drop across R1 and R2

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