# Linear Integrated Circuit Questions and Answers – Peak Detector, Sampling & Hold Circuit and Absolute Value Output Circuit

This set of Linear Integrated Circuit Multiple Choice Questions & Answers (MCQs) focuses on “Peak Detector, Sampling & Hold Circuit and Absolute Value Output Circuit “.

1. Which circuit can be used as a full wave rectifier?
a) Absolute vale output circuit
b) Positive clipper with two diodes
c) Negative clipper with two diodes
d) Peak clampers

Explanation: Absolute value output circuit produces an output signal that swings positively only, regardless of the polarity of the input signal; because of the nature of its output wave form, the circuit is used as full wave rectifier.

2. For the circuit shown below find the output voltage

a) Vo (+) = +10 v
b) Vo (+) = +12v
c) Vo (+) = +7v
d) None of the mentioned

Explanation: The voltage at the terminal V1 = (Vp -Vd1) /2
V1 = (12-0.7) /2 = 5.65 v (Vd1= voltage drop across diode=0.7)
Similarly, the voltage at the negative terminal V2 = (Vo -Vd3 ) /2 = (Vo – 0.7) /2
Since Vid ≅ 0v , ∴ V1 = V2
Vo = (5.65 *2 ) + 0.7 = 12v.

3. Determine the output waveform for the circuit

Where input = 2 Vp sine wave with time period 0.2ms.
a)

b)

c)

d) None of the mentioned

Explanation: Given circuit is the thevenin equivalent of absolute value output circuit. Therefore, the output will be equal to the input regardless of polarity.
Therefore, Vo (+) = Vo (-) = 2 Vp sine wave with 0.2 ms time period. So, the output wave form will be a full wave rectified output of 2v amplitude,

4. What is the alternate method to measure the values of non-sinusoidal waveform other than ac voltmeter?
a) Clipper
b) Clamper
c) Peak detector
d) Comparator

Explanation: A conventional ac voltmeter is designed to measure rms value of the pure sine wave whereas, the peak value of the non-sinusoidal wave forms can be a peak detector.

5. State the condition needed to be satisfied by peak detector for proper operation of circuit.
a) CRd ≤ T/10 and CRL ≥ 10T
b) CRd ≤ 10T and CRL ≥ T/10
c) CRd ≥ T/10 and CRL ≤ 10T
d) CRd ≥ 10T and CRL ≤ T/10

Explanation: For proper operation of the circuit, charging and discharging time constant must satisfy the following: CRd ≤ T/10 and CRL ≥ to 10T.
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6. The resistor in the peak detector are used to
a) To maintain proper operation
b) Protect op-amp from damage
c) To get shaped non-sinusoidal waveform
d) None of the mentioned

Explanation: The resistor is used to protect the op-amp against the excessive discharge current, especially when the power supply is switched off.

7. How the recovery time of the op-amp is reduced?
a) Diode is connected at the output of amplifier
c) Forward biased diode resistor
d) Discharge capacitor

Explanation: The diode connected at the output of op-amp conducts during negative half cycle of input voltage. Hence, prevent the op-amp from going into negative saturation. This in turn helps to reduce the recovery time of the op-amp.

8. How to detect the negative peaks of input signals in the peak detector given below?

a) Reversing D1 diode
b) Reversing D1 and D2 diodes
c) Reversing D2 diode
d) Charging the positions of D1 and D2

Explanation: The negative peaks of the input signal Vin can be detected by reversing diodes D1 and D2.

9. In the sample and hold circuit, the period during which the voltage across capacitor is equal to input voltage
a) Sample period
b) Hold period
c) Delay period
d) Charging period

Explanation: The time periods of the sample and hold control voltage during which the voltage across capacitor is equal to the input voltage are called sample period.

10. During which period the op-amps output of sample and hold circuits is processed?
a) Delay period
b) Sample and hold period
c) Sample period
d) Hold period

Explanation: Hold period is the period during which the voltage across the capacitor is constant and the output of the op-amp is processed or observed during hold periods.

11. Which IC is mostly preferred for sample and hold circuit?
a) µ771
b) IC741
c) LF398
d) µ351

Explanation: LF398 have significant reduction in size and improved performance and require only an external storage capacitor.

12. Sample and hold circuit are used in
a) Analog to Digital modulation
b) Digital to analog modulation
c) Pulse position modulation
d) All of the mentioned

Explanation: All types of modulation involve taking samples of an input signal and hold on to it last sample value until the input is sampled.

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