Characteristics of Operational Amplifier MCQ - Objective Question Answer for Operational Amplifier Characteristics Quiz

101. Compute the output voltage for the given circuit

A. -2.6v
B. -27.8v
C. -26.7v
D. -0.267v

Answer: C

The given circuit is a current-to-voltage converter.

Since V₁ = 0v and V₁ = V₂.

= > i_in = V_in/R₁ = 4/ 1.5kΩ = 2.67mA.

The output voltage

V_o = -i_in*R_F = -2.67mA*10kΩ = -26.7v.

102. At what condition an inverting amplifier works as an inverter

A. R₁ = R_F+ R_L
B. R_F = ( R₁*V_in)/R_L
C. R₁ = R_F
D. R₁ = V_o/(V_in*R_L)

Answer: C

If R₁ = R_F, the inverting amplifier will work as an inverter.

103. Why differential amplifiers are preferred for instrumentation and industrial applications?

A. Input resistance is low
B. Produce amplified output
C. Amplify individual input voltage
D. Reject common-mode voltage

Answer: D

Differential amplifiers are preferred in these applications because they are better able to reject common-mode voltage than single input circuits and present balanced input impedance.

104. Which of the following is a combination of inverting and non-inverting amplifiers?

A. Differential amplifier with one op-amp
B. Differential amplifier with two op-amps
C. Differential amplifier with three op-amps
D. Differential amplifier with four op-amps

Answer: A

In a differential amplifier with one op-amp both the inputs are connected to separate voltage sources. So, if any one of the sources is reduced to zero, a differential amplifier acts as an inverting or non-inverting amplifier.

105. What will be the output voltage when V_x = 0v?
(Where V_x –> inverting input terminal of differential amplifier with one op-amp)

A. V_o = -(1+R _F/R₁)*V₁
B. V_o = -(1- R _F/ R₁)*V₁
C. V_o = (1+ R _F/ R₁)*V₁
D. V_o = (R _F/ R₁)*V₁

Answer: C

When V_x = 0v, the configuration is a non-inverting amplifier.

V_o = (1+ R _F/ R₁)*V₁

106. Compute the output voltage from the following circuit diagram?

A. -17v
B. -27v
C. -39v
D. -15v

Answer: B

Since V_B = 0, the configuration becomes an inverting amplifier. Hence, the output due to V_A is

V_o = -(R_F/R₁)*V_A

= -(15kΩ/1.5kΩ)*2.7v

= -10*2.7 = -27v.

107. Compute the output voltage if the input voltage is reduced to zero in a differential amplifier with one op-amp?

A. Inverted Voltage
B. Same as the input voltage
C. Amplified inverted voltage
D. Cannot be determined

Answer: D

It is not mentioned clearly whether inverting input or non-inverting input is reduced to zero. Therefore, the output cannot be determined.

108. The difference between the input and output voltage is -1v and 17v. Calculate the closed-loop voltage gain of differential amplifier with one op-amp?

A. -51
B. 34
C. -17
D. 14

Answer: C

Voltage gain of differential amplifier with one op-amp

A_D = Output voltage / Difference of input voltage

= > A_D = 17v/-1v = -17v.

109. For the differential amplifier given below, determine the V_x and R_F values. Assume that the circuit is initially nulled.

A. V_x = -8v, R_F = 9.9kΩ
B. V_x = 8v, R_F = 9.9kΩ
C. V_x = -8v, R_F = -9.9kΩ
D. V_x = 8v, R_F = -9.9kΩ

Answer: D

The closed loop voltage gain, A_D = -(R_F/R₁)

= > RF = -3*3.3kΩ = -9.9kΩ

The net output is given is

V_O = -(RF /R1)*(Vx-Vy)

= > V_x = V_y– V_o (-R₁ /R_F)

= > V_x = 6+6(3.3kΩ/9.9kΩ) = 6+2 = 8v.

110. The gain of a differential amplifier with one op-amp is the same as that of

A. The inverting amplifier
B. The non-inverting amplifier
C. Both inverting and non-inverting amplifier
D. None of the mentioned

Answer: A

The gain of the differential amplifier is given as A_D = -(R_F /R₁), which is equivalent to the output voltage obtained from the inverting amplifier.

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