MCQ on Operational Amplifier with Answers

Practice MCQ on Operational Amplifier with Answers

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MCQ on Operational Amplifier with Answers

Q1. An amplifier has a voltage gain Av = 1000, input impedance 1 KΩ and output impedance 500 Ω A fraction βv = 0.1 of the output voltage is fed back in the serie in opposition to the input voltage. The input and output impedance after the feedback are given respectively by the approximate values.

(a) 100 kΩ and 5 Ω
(b) 1 kΩ and 5 Ω
(c) 10 Ω and 50 Ω
(d) 100 Ω and 100 Ω

Q2. An amplifier of gain 1000 is made into a feedback amplifier by feeding 9.9% of its output voltage in series with the input opposing. If fL = 20 Hz and fH = 200 kHz for the amplifier without feedback, then due to the feedback.

(a) The gain decreasse by 10 times
(b) The outputresistance increases by 10 times
(c) The fH increases by 100 times
(d) The input resistance decreases by 100 times.

Q3. An amplifier has a 40 dB gain. Its gain may change by 10% due to change in its parameters. Negative feedback is used to reduce this change only to 1%. Then the value of feedback factor β is

(a) β = 0.1
(b) β = 10
(C) β = 0.09
(d) β = 0.001

Q4. The input impedance of an amplifier increases by the introduction of feedback. It is due to :

(a) positive feedback
(b) current series negative feedback
(c) current shunt negative feedback
(d) voltage shunt negative feedback

Q5. In a RC coupled amplifier, the reduction in voltage gain in the high frequency range results due to:

(a) coupling capacitor
(b) shunt capacitance in the circuit
(c) series capacitance in the circuit
(d) bypass capacitor in the inner circuit

Q6. In a amplifier the negative feedback is a process where a portion of output signal is fed to the input of the normal amplifier with the condition that the input signal is:

(a) in phase
(b) 90° out of phase
(c) 180° out of phase
(d) any arbitrary phase

Q7. Which oscillator is characterized by a split capacitor in its tank circuit?

(a) RC phase shift oscillator
(b) Colpitts oscillator 
(c) Wien bridge oscillator 
(d) None of the above 

Q8. In which type of power amplifier does the output current flow for the entire cycle of input signal?

(a) Class C
(b) Class AB
(c) Class B
(d) Class A

Q9. In an amplifier with the negative feedback, bandwidth is _________ and voltage gain is _________.

(a) Bandwidth is decreased by a factor (1+Aβ) and voltage gain decreases
(b) Bandwidth is decreased by factor β and voltage gain remains same
(c) Bandwidth is increased by the factor (1+Aβ) and voltage gain is reduced
(d) Bandwidth remains the same and voltage gain increases

Q10. The crystal oscillator is a constant frequency oscillator due to:

(a) Rigidity
(a) Vibrations
(c) Low Q
(d) High Q

Q11. A Series-Series feedback amplifier is

(a) Voltage amplifier
(b) Current amplifier
(c) Transresistance
(d) Transconductance

Q12. The value of C required for sinusoidal oscillation of frequency = 2 kHz in the given circuit is:

(a) 1/2πμF
(b) 1/4πμF
(c) 1/πμF
(d) None of these

Q13. The frequency of oscillation of a tuned-collector oscillator having L = 30 μH and C = 300 pF is nearby

(a) 267 kHz
(b) 1677 kHz
(c) 1.68 kHz
(d) 2.67 MHz

Q14. Another name for a unity gain amplifier is

(a) Difference amplifier
(b) Comparator
(c) Single-ended
(d) Voltage follower

Q15. Which of the following is correct about the gain (in dB) of a cascade amplifier?

(a) Total gain is a sum of individual gains
(b) Total gain is a product of voltage and current gains
(c) Total gain is a product of individual gains
(d) Total gain is a ratio of individual gains

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