Linear Integrated Circuit Questions and Answers – Voltage Series Feedback Amplifier – 1

This set of Linear Integrated Circuit Multiple Choice Questions & Answers (MCQs) focuses on “Voltage Series Feedback Amplifier – 1”.

1. Specify the voltage gain of non-inverting amplifier with feedback amplifier with and without feedback?
a) A= Vo/Vid, AF = Vf/Vo
b) A= Vf/Vid, AF= Vo/Vf
c) A= Vo/Vid, AF= Voin
d) A= Vf/Vid, AF = Vf/Vin
View Answer

Answer: c
Explanation: The voltage gain of op-amp with feedback is the open loop voltage gain, A=Vo /Vid. The voltage gain of op-amp without feedback is the closed loop voltage gain, AF = Vo /Vin.

2. If the feedback voltage and the output voltage are given as 10v and 4v. Find the gain of the feedback circuit in voltage-series feedback amplifier?
a) 2.5v
b) 40v
c) 3v
d) 6.2v
View Answer

Answer: a
Explanation: Gain of feedback, B = Vf /Vo = 10v/4v = 2.5v.

3. How is the difference voltage calculated in closed loop non-inverting amplifier?
a) Vid= Vo – Vf
b) Vid= Vin – Vf
c) Vid= Vo – Vin
d) Vid= Vf – Vin
View Answer

Answer: b
Explanation: Although, the input is given to the non-inverting terminal of op-amp, the difference voltage is equal to the input voltage minus feedback voltage is Vid= Vin – Vf.
advertisement
advertisement

4. Why the feedback circuit is said to be negative for voltage series feedback amplifier?
a) Feedback voltage is 180o out of phase with respect to input voltage
b) Input voltage is 180o out of phase with respect to feedback voltage
c) Feedback voltage is in same phase with respect to input voltage
d) Input voltage is in same phase with respect to feedback voltage
View Answer

Answer: a
Explanation: Voltage series feedback amplifier have the difference voltage, Vid = Vin-Vf. Therefore, the feedback voltage always opposes the input voltage and is out of phase by 180o with respect to input voltage. Hence, the feedback is said to be negative.

5. Determine the closed loop voltage gain from the given circuit. (Where gain of op-amp= 105).
Determine the closed loop voltage gain from the given circuit
a) 1090.9
b) 9821.43
c) 9166.66
d) 10000
View Answer

Answer: b
Explanation: The closed loop voltage gain , AF = {[A*(R4+R5)]/[(RF+R1+(A*R1)]} = [105*(10kΩ+1kΩ)]/[1kΩ+10kΩ+(105*1kΩ)] =11×108/112000
=> AF = 9821.43.

6. Express closed loop voltage gain (AF) in terms of open loop gain (A) and feedback circuit gain (B)?
a) AF = A/AB
b) AF = 1+ (A/AB)
c) AF = A/(1+AB)
d) AF = AB/(1+A)
View Answer

Answer: c
Explanation: The closed loop voltage gain in terms of open loop gain and feedback circuit gain is expressed as AF = A/(1+AB).
Sanfoundry Certification Contest of the Month is Live. 100+ Subjects. Participate Now!

7. Which factor determines the gain of the voltage series feedback amplifier?
a) Open loop voltage gain
b) Feedback voltage
c) Ratio of two resistors
d) Gain of feedback circuit
View Answer

Answer: c
Explanation: In setting the gain of the voltage series feedback amplifier, the ratio of two resistors is important and not the absolute value of these resistors. For example: If a gain of 11 is desired, we choose R1=1kΩ and R1=10kΩ or R1=100Ω and RF= 1kΩ.
advertisement

8. For the feedback circuit of voltage series feedback amplifier, find the feedback voltage for the specifications: R1=1kΩ, RF = 10kΩ and Vo= 25v.
a) 12.5v
b) 22v
c) 0.9v
d) 2.3v
View Answer

Answer: d
Explanation: Find the feedback voltage for the specifications of voltage series feedback amplifier
The feedback voltage, Vf = (R1*Vo)/(R1+RF) = (1kΩ*25v)/(1kΩ+10kΩ) = 2.272v ≅ 2.3v.

9. What must be the value of external components used in voltage series feedback amplifier?
a) Less than 1MΩ
b) Less than 10MΩ
c) Less than 100MΩ
d) Less than 0.1MΩ
View Answer

Answer: a
Explanation: All external components value should be less than 1MΩ. So, that they do not adversely affect the internal circuitry of the op-amp.
advertisement

10. Find the block diagram representation of non-inverting amplifier with feedback?
a) Non-inverting amplifier block diagram
b) Find the inverting amplifier with feedback from the given diagram
c) Find the standard form of amplifier from the given diagram
d) Find the system with feedback from the gjven diagram
View Answer

Answer: a
Explanation: The mentioned block diagram is the standard form for representing a system with feedback.

11. Define the input resistance with feedback for voltage series feedback amplifier?
a) RIF = (1-AB)
b) RIF = (AB-1)
c) RIF = (1+AB)
d) None of the mentioned
View Answer

Answer: c
Explanation: In feedback amplifier, the input resistance of the op-amp with feedback is (1+AB) times that of without feedback.

12. When the non-inverting input terminal of an op-amp is equal to that of the inverting input terminal (ideally)
a) a–>∞
b) Vid ≅ 0
c) AF = 1+( RF / R1)
d) All of the mentioned
View Answer

Answer: d
Explanation: When the input at both the terminal are equal, the difference input voltage, Vid=Vin1– Vin2.
=> Vid≅0 (∵Vin1= Vin2)
The open loop voltage gain, A= Vo/ Vid = Vo/0 = ∞ and
the closed loop voltage gain, AF= Vo/ Vin = 1+ (RF/ R1).

Sanfoundry Global Education & Learning Series – Linear Integrated Circuits.

To practice all areas of Linear Integrated Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

Subscribe to his free Masterclasses at Youtube & discussions at Telegram SanfoundryClasses.