Top Operational Amplifier MCQ [Free PDF] - Objective Question Answer for Operational Amplifier Quiz

51. Find the disadvantage in the following 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

Answer: B

The output taken at the junction of R₁ and R₂ increases the voltage shift. However, the disadvantage is that the signal voltage gets attenuated by R₂.

= > R₂/(R₁ + R₂).

52. A Differential Amplifier should have the collector resistor’s value (RC1 & RC2) as

A. 5kΩ, 5kΩ
B. 5Ω, 10kΩ
C. 5Ω, 5kΩ
D. 5kΩ, 10kΩ

Answer: A

The values of collector current will be equal in the differential amplifier (RC1 = RC2) i.e 5kΩ, 5kΩ

53. A Differential Amplifier amplifies

A. Input signal with higher voltage
B. Input voltage with smaller voltage
C. Sum of the input voltage
D. Difference between two signals.

Answer: D

The purpose of the differential amplifier is to amplify the difference between two signals.

54. The value of emitter resistance in Emitter Biased circuit are RE1 = 25kΩ & RE2 = 16kΩ. Find RE

A. 9.756kΩ
B. 41kΩ
C. 9.723kΩ
D. 10kΩ

Answer: A

In emitter biased circuit, RE1 & RE2 are connected in parallel combination.

⇒ RE = RE1 II RE2

= (RE1 × RE2)/(RE1+RE2)

= (25kΩ × 16kΩ)/(25kΩ+16kΩ) = 9.7561kΩ.

55. If the output is measured between two collectors of transistors, then the Differential amplifier with two input signals is said to be configured as

A. Dual Input Balanced Output
B. Dual Input Unbalanced Output
C. Single Input Balanced Output
D. Dual Input Unbalanced Output

Answer: A

When two input signals are applied to the base of the transistor, it is said to be Dual Input. When both collectors are at the same DC potential with respect to ground, then it is said to be a Balance Output.

56. A differential amplifier is capable of amplifying

A. DC input signal only
B. AC input signal only
C. AC & DC input signal
D. None of the Mentioned

Answer: C

Direct connection between stages removes the lower cut-off frequency imposed by the coupling capacitor; therefore it can amplify both AC and DC signals.

57. In an ideal Differential Amplifier, if the same signal is given to both inputs, then the output will be

A. Same as input
B. Double the input
C. Not equal to zero
D. Zero

Answer: D

In an ideal Differential Amplifier, if the same signal is given to both inputs, then the output will be Zero.

In an ideal amplifier, the Output voltage

⇒ Vout = V_in1−V_in2= 0

58. An emitter bias Dual Input Balanced Output differential amplifier has VCC = 20v, β = 100, VBE = 0.7v, RE = 1.3kΩ. Find IE

A. 7.42 mA
B. 9.8 mA
C. 10 mA
D. 8.6 mA

Answer: A

Emitter current can be found out by substituting the values in the equation,

⇒ IE = (VEE − VBE)/(2RE)

= (20v − 07v)/(2 × 1.3kΩ) = 7.42 mA.

59. Find IC, given VCE = 0.77v, VCC = 10v, VBE = 0.37v and RC = 2.4kΩ in Dual Input Balanced Output differential amplifier

A. 0.4 mA
B. 0.4A
C. 4 mA
D. 4A

Answer: C

Substitute the values in the collector to the emitter voltage equation,

VCE = VCC+ VBE-RC IC

⇒IC = (VCC-VCE+VBE)/RC

= (10v-0.77v+0.37v)/2.4kΩ = 4 mA

60. Find the correct match of the following voltage gain

Configuration	Voltage gain and Input resistance
1. Single Input Unbalanced Output	i. A_d = Rc/re , R_i1 R_i2 = 2β_acRE
2. Dual Input Balanced Output	ii. A_{d = Rc/2re , Ri1 Ri2 = 2βacRE}
3. Single Input Balanced Output	iii. A_d = Rc/re , R_i = 2β_acRE
4. Dual Input Unbalanced Output	iv. A_d = Rc/2re , R_i = 2β_acRE

A. 1-i , 2-iii, 3-iv, 4-ii
B. 1-iv, 2-ii, 3-iii, 4-i
C. 1-ii, 2-iv, 3-i , 4-iii
D. 1-iii, 2-i, 3-ii, 4-iv

Answer: D

The correct match of the following voltage gain

Configuration	Voltage gain and Input resistance
1. Single Input Unbalanced Output	A_d = Rc/re , R_i = 2β_acRE
2. Dual Input Balanced Output	A_d = Rc/re , R_i1 R_i2 = 2β_acRE
3. Single Input Balanced Output	A_{d = Rc/2re , Ri1 Ri2 = 2βacRE}
4. Dual Input Unbalanced Output	A_d = Rc/2re , R_i = 2β_acRE

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