# Electric Circuits Questions and Answers – Operational Amplifier Terminals,Terminal Voltages and Currents

This set of Electric Circuits test focuses on “Operational Amplifier Terminals,Terminal Voltages and Currents”.

1. Op-amp was introduced by __________
a) Fairchild
b) Maxwell
c) Rutherford
d) Sahani

Explanation: Op-amp was introduced by Fairchild semiconductor in 1968.

2. The number of terminals in an Op-amp ______________
a) 6
b) 2
c) 5
d) 3

Explanation: Inverting input, the Non-inverting input, Output, Positive power supply, Negative power supply.

3. The Op-amp is a type of ___________
a) Differential amplifier
b) Integrated amplifier
c) Isolation amplifier
d) Feedback amplifier

Explanation: The Op-amp is a type of differential amplifier.

4. In the circuit of Op-amp given V- stands for _________

a) Non-inverting input
b) Non-inverting output
c) Inverting input
d) Inverting output

Explanation: V+: Non-inverting input and V- : Inverting input.

5. When the input voltage difference is small in magnitude, the Op-amp behaves as ____________
a) Non-linear device
b) Linear device
c) Complex device
d) Bipolar device

Explanation: When │vp-vn│is small then Op-amp acts as a linear device as the output voltage is a linear function of input voltages.

6. If the output voltage is not a linear function of input voltage then ____________
a) Op-amp acts a linear device
b) Op-amp acts as a non-linear device
c) Op-amp acts a polar device
d) Op-amp acts as an inverter

Explanation: If output voltage is not a linear function of input voltage then Op-amp acts as a non-linear device.

7. The negative feedback causes the input voltage difference to ____________
a) 1
b) Increase
c) Decrease
d) 0

Explanation: Negative feedback means a signal is fed back from output terminals to the non-inverting input terminals and this results in a decrease in input voltage difference.

8. Find the gain for the following circuit.

a) -2
b) 2
c) -1
d) 1

Explanation: In this circuit, the only node is at the negative terminal of the Op-amp (say Vn) and by ideal rules of Op-amp, Vn= Vp =0(in this circuit). Gain= Vout/Vin= -R2/R1.

9. Calculate the gain for the Op-amp given.

a) 0.719
b) 2.572
c) 1.390
d) 1.237

Explanation: Gain= Vout/Vin= -R2/R1 = -5.98*10-3/4.3*10-3.

10. Given Op-amp is ideal. Calculate vo if va=1v and vb=0v.

a) -4v
b) -2.5v
c) 4v
d) 2.5v

Explanation: In the given circuit, a negative feedback exists between Op-amp’s output and its inverting input (voltage here is 0, as vp =vb=0 and vn=vp). Node-voltage equation is i50=i125=i0.
i50= (va-vn)/50 =1/50 mA.
I125= (v0-vn)/125 = v0/125 mA.
1/50 + v0/125 = 0.
v0 is -2.5volts.

Sanfoundry Global Education & Learning Series – Electric Circuits.

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