Linear Integrated Circuit Multiple Choice Questions 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
Clarification: 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
Clarification: 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.
4. What is the alternate method to measure the values of non-sinusoidal waveform other than ac voltmeter?
C. Peak detector
Clarification: 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
Clarification: For proper operation of the circuit, charging and discharging time constant must satisfy the following: CRd ≤ T/10 and CRL ≥ to 10T.
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
Clarification: 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
B. Load resistor
C. Forward biased diode resistor
D. Discharge capacitor
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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?
Clarification: 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
Clarification: All types of modulation involve taking samples of an input signal and hold on to it last sample value until the input is sampled.