# Operational Amplifier Internal Circuit – 2 MCQ’s

This set of Signals & Systems Multiple Choice Questions & Answers (MCQs) focuses on “Operational Amplifier Internal Circuit – 2″.

1. How the differential mode gain is expressed using ‘h’ parameter for a single ended output?
a) – hfeRC/hie
b) 1/2×(hfeRC)/hie
c) – 1/2×hfeRC
d) None of the mentioned

2. Find Common Mode Rejection Ration, given gm =16MΩ-1, RE=25kΩ
a) 58 db
b) 40 db
c) 63 db
d) 89 db

3. How are the arbitrary signal represented, that are applied to the input of transistor? (Assume common mode signal and differential mode signal to be VCM & VDM respectively).
a) Sum of VCM & VDM
b) Difference of VCM & VDM
c) Sum and Difference of VCM & VDM
d) None of the mentioned

4. In differential amplifier the input are given as V1=30sin⁡Π(50t)+10sin⁡Π(25t) , V2=30sin⁡Π(50t)-10 sin⁡Π(25t), β0 =200,RE =1kΩ and RC = 15kΩ. Find the output voltages V01, V02 & gm=4MΩ-1
a) V01=-60[10 sin⁡Π(25t) ]-6.637[30sin⁡Π(50t) ], V02=60[10 sin⁡Π(25t) ]-6.637[30sin⁡Π(50t) ].
b) V01=-6.637[10 sin⁡Π(25t) ]-60[30sin⁡Π(50t) ], V02=6.637[10 sin⁡Π(25t) ]-60[30sin⁡Π(50t) ].
c) V01=-60[30 sin⁡Π(50t) ]-6.637[10sin⁡Π(25t) ], V02=60[30 sin⁡Π(50t) ]-6.637[10sin⁡Π(25t) ].
d) V01=-6.637[30 sin⁡Π(50t) ]-60[10sin⁡Π(25t) ], V02=6.637[30 sin⁡Π(50t) ]-60[10sin⁡Π(25t) ].

5. To increase the value of CMRR, which circuit is used to replace the emitter resistance Re in differential amplifier?
a) Constant current bias
b) Resistor in parallel with Re
c) Resistor in series with Re
d) Diode in parallel with Re

6. How to improve CMRR value
a) Increase common mode gain
b) Decrease common mode gain
c) Increase Differential mode gain
d) Decrease differential mode gain

7. If the value of Common Mode Rejection Ratio and Common Mode Gain are 40db and -0.12 respectively, then determine the value of differential mode gain
a) 0.036
b) -1.2
c) 4.8
d) 12

8. What is the purpose of diode in differential amplifier with constant current circuit?
a) Total current independent on temperature
b) Diode is dependent of temperature
c) Transistor is depend on temperature
d) None of the mentioned

9. Define total current (IQ) equation in differential amplifier with constant current bias current
a) IQ=1/R3×(VEE/R1+R2)
b) IQ =(VEE×R2)/(R1+R2)
c) IQ=1/R3×(VEE×R2/R1+R2)
d) IQ)=R3×(VEE/R1+R2)

10. When will be the mirror effect valid
a) β≫1
b) β=1
c) β<1
d) β≠1

11. Constant current source in differential amplifier is also called as
a) Current Mirror
b) Current Source
c) Current Repeaters
d) All of the mentioned

12. Calculate the value of reference current and input resistor for current mirror with IC=1.2μA & VCC=12v. Assume β=50.
a) 1.248mA, 9kΩ
b) 1.248mA, 9.6kΩ
c) 1.248mA, 9.2kΩ
d) 1.2mA, 9.6kΩ

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