Linear Integrated Circuit Questions and Answers – AC Amplifiers with Single Supply Voltage

This set of Linear Integrated Circuit Multiple Choice Questions & Answers (MCQs) focuses on “AC Amplifiers with single supply voltage”.

1. How an AC amplifier can be powered by a single supply voltage, produces voltage swing?
a) By inserting a voltage divider at the inverting input
b) By inserting a voltage divider at the non-inverting input
c) By inserting a voltage divider at the output
d) By inserting a voltage divider at the feedback circuit
View Answer

Answer: b
Explanation: A positive dc level is intentionally inserted using a voltage-divider network at the non-inverting input terminal, so that output can swing both positively as well as negatively.

2. Given below are the circuits connected to the non-inverting input terminal of AC amplifier. Choose the circuit which produces positive output swing equal the negative?
a)
Find input terminal of AC amplifier from the given diagram
b)
Find the positive output swing and dc level from the given diagram
c)
Find the voltage divider at  inverting input from the given diagram
d) None of the mentioned
View Answer

Answer: b
Explanation: The circuit is generally a positive dc level (+Vcc/2), so the positive output swing will be equal to negative and this is accomplished by selecting R2 = R3.

3. What is the output waveform at the point VO1 in the given circuit? (Take R1=1kΩ and RF=5kΩ)
Find the output waveform at the point VO1 from the given circuit
a)
Find the AC output from the given diagram
b)
Input is applied at inverting terminal so the AC output will be riding on a DC level
c)
Find DC level of Vcc/2 from the given diagram
d)
Find the input applied at inverting terminal from the given diagram
View Answer

Answer: c
Explanation: The input is applied at the inverting terminal so, the AC output will be riding on a DC level of (+Vcc/2) volts and will be inverted.
Vo = -(RF/R1)×Vin = -(5kΩ/1kΩ)×6Vp = 30Vp sinewave.
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4. The input waveform of an AC non-inverting amplifier with single supply is given below. Find the output waveform?
Find output waveform which has input waveform of an AC non-inverting amplifier from circuit
a)
Find the output waveform from the given diagram
b)
Find the coupling capacitor from the given diagram
c)
Find output blocks from the given diagram
d)
Find the same phase of input signal from the given diagram
View Answer

Answer: b
Explanation: The coupling capacitor at the output blocks the AC output signal riding on a DC level of (+Vcc/2) volts and the resultant waveform will be AC. In non-inverting amplifier, the output will be of the same phase as that of input signal.

5. Find the maximum output voltage swing of an AC inverting amplifier using op-amp 741C?
a) +15Vpp
b) ±15Vpp
c) ±13Vpp
d) +13Vpp
View Answer

Answer: a
Explanation: The value of power supply for 741 op-amp=±15v. Therefore, the ideal maximum output voltage swing for an AC amplifier with single power supply = +Vcc = +15v.
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6. Determine the lower cut-off frequency of the circuit.
Determine the lower cut-off frequency of the circuit
a) 21.3Hz
b) 12.15Hz
c) 1.35Hz
d) None of the mentioned
View Answer

Answer: d
Explanation: The input resistance of the amplifier is RIF =(R2 ||R3) || [ri×(1+AB)] –> equ 1
As [ri×(1+AB)] >> R2
=> Therefore, equ 1 becomes
RIF ≅ R2 || R3 = 100kΩ || 100kΩ = (100×100)/(100+100) = 50kΩ.
=> Rin = Ro = 150Ω.
∴ Lower cut off frequency, fL= 1/[2πCi×(RIF+Ro)] = 1/[2π×0.47µF×(50kΩ+150Ω)] = 6.75Hz.

7. In differential op-amp configuration a subtractor is called as
a) Summing amplifier
b) Difference amplifier
c) Scaling amplifier
d) All of the mentioned
View Answer

Answer: c
Explanation: In a subtractor input signals can be scaled to the desired values by selecting appropriate values for the external resistors. Therefore, this circuit is referred to as scaling amplifier.
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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.

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

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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.

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