Voltage Regulators – 2 MCQ’s

This set of Analog Electronic Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Voltage Regulators – 2″.

1. Consider the op-amp circuit shown.

The breakdown voltage of the Zener is 5V. β for the transistor is 100. R1=10kΩ, R2=90kΩ, R3=30kΩ, R4=50kΩ. Calculate the total output voltage.
a) 20V
b) 30V
c) 5V
d) 50V

2. Consider the following circuit. Find the power dissipation of the transistor given that the diode breakdown voltage is 5V, R1=20kΩ, R2=100kΩ, R3=200kΩ, R4=10Ω. The source voltage VS=20V.

a) 12.12W
b) 9.375W
c) 9.27W
d) 10.575W

3. In a power supply, the output voltage can vary due to multiple reasons. Which of these is not true if it is found that the output voltage is constant?
a) The voltage stability factor is very high
b) The output resistance is zero
c) The temperature coefficient is zero
d) The voltage stability factor is very small

4. In the Zener controlled series regulator shown below, find the current through the Zener diode.

Given that the Zener diode breakdown voltage is 5V, the source voltage is 15V, the output voltage is 10V, R4 = 2kΩ, β=99, R1=2kΩ.
a) 5.05 mA
b) 4.95 mA
c) 3.33 mA
d) 0

5. The following is a shunt regulator. Find maximum power dissipation of the Zener diode and transistor, given that the source voltage varies from 20-40V, the Zener breakdown voltage is 5V, the output voltage is 10V, the resistance R1=50Ω, R2=20kΩ, β=99, VBE=0.5V.

a) PTransistor = 5.12 W, PZener = 0.051 W
b) PTransistor = 0.41 W, PZener = 0.57 W
c) PTransistor = 5.94 W, PZener = 0.057 W
d) PTransistor = 6.22 W, PZener = 5.66 W

6. In a transistorized series regulator, how is the overload and short-circuit protection provided?
a) By the use of a thermistor
b) By using two additional diodes and a current sensing resistor to protect the series transistor
c) By using a diode and an additional resistor to protect the transistor
d) By using a diode along with a capacitor of a small capacitance value in series

7. Consider the circuit shown and find the percentage increase in power dissipation of the transistor if the source voltage increases by 10%.

Given that the breakdown voltage is 5V, R1=10kΩ, R2=100kΩ, R3=200kΩ, R4=10Ω. The source voltage VS=25V.
a) 10%
b) 20.22%
c) 14.28%
d) 15.66%

8. What is not related to a transistorized series regulator?
a) The output can be varied by using a variable resistor
b) The output is independent of temperature
c) The overload and short circuit protection is not required
d) The circuit has negative feedback responsible for regulation

9. What is the output of the IC 7924?
a) 12V
b) -12V
c) 24V
d) -24V

10. In the IC 7805, what is the minimum input voltage for proper functioning?
a) 5V
b) 6V
c) 7V
d) 8V

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