# Analog Circuits Mcqs

Q:

In the IC 7805, what is the minimum input voltage for proper functioning?

 A) 5V B) 6V C) 7V D) 8V

Explanation: For a fixed voltage IC regulator, the input voltage should be at least 2V greater than the output voltage. A minimum voltage of 2V should be allowed to drop in the internal circuit of the IC.

7
Q:

What is the output of the IC 7924?

 A) 12V B) -12V C) 24V D) -24V

Explanation: The IC of series 78xx and 79xx are fixed voltage regulators, wherein the 78 represents those with a positive output and 79 is for those with a negative output. The xx value represents the magnitude of the output voltage being achieved. For proper operation, the input voltage should be at least 2V greater than the output voltage.

8
Q:

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

Answer & Explanation Answer: B) By using two additional diodes and a current sensing resistor to protect the series transistor

Explanation: Series transistor can be protected by connecting two additional diodes and a current sensing resistor to the circuit. When the load current is smaller, the diode is off and load current is through the transistor and the new resistor. When the load current increases, the voltage drop across the new resistor increases and soon the diodes start conduction. A limiting current flows through the transistor.

9
Q:

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

Explanation: In a transistorized series regulator, the Zener diode maintains emitter voltage. An increase in output is canceled by a decrease in the output. The circuit has negative feedback for this regulation. The output may be varied by using a variable resistor and change in output due to temperature due to the Zener diode is canceled by the change in VBE of the transistor. However, when the load is reduced, or an accidental short-circuit occurs, overload and a short circuit occurs, and protection is needed to prevent that.

7
Q:

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

Answer & Explanation Answer: A) The voltage stability factor is very high

Explanation: Not available for this question

8
Q:

Which of these is a not drawback of Zener diode shunt regulator?

 A) The output voltage is fixed B) The output voltage can vary with temperature C) Variation in load current needs to be minimal D) It is difficult to design

Explanation: The Zener diode shunt regulator is a simple voltage regulator circuit that provides a fixed output voltage. However, due to the presence of the Zener diode, the output is temperature dependent because the breakdown voltage of Zener diode depends on temperature. When load current varies a lot, then Zener current also varies which causes a change in output voltage.

12
Q:

 A) The process of keeping the load voltage constant irrespective of any change in AC supply B) The process of keeping the load voltage constant irrespective of variations in load current C) The process of keeping load voltage constant irrespective of variations in source current D) The process of keeping load current constant irrespective of variations in AC supply

Explanation: Load regulation is the process of keeping VO constant irrespective of variations in load current. The line voltage is taken to be constant during load regulation.

7
Q:

What is line regulation?

 A) The process of keeping Zener diode voltage constant inspite of changes in AC supply B) The process of keeping load voltage constant irrespective of the fluctuation in AC supply or the line voltage C) The process of keeping load voltage constant irrespective of fluctuation in load current D) The process of keeping Zener current constant irrespective of fluctuation in AC supply

Answer & Explanation Answer: B) The process of keeping load voltage constant irrespective of the fluctuation in AC supply or the line voltage

Explanation: Line regulation is the process of keeping the load voltage constant, irrespective of fluctuation in AC supply or the line voltage. In line regulation, the load current is considered constant.