# Electronic Devices and Circuits Questions and Answers – The Ideal Diode

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “The Ideal Diode”.

1. For an ideal diode which of the following is true?
a) It allows the passage of current in the forward bias with zero potential drop across the diode
b) It does not allow the flow of current in reverse bias
c) All of the mentioned
d) None of the mentioned

Explanation: Both of the facts mentioned hold true for an ideal operational amplifier.
Explanation: Vd = Vi – Vo.

3. The figure below shows a circuit for charging a 12-V battery. If Vs is a sinusoid with 24-V peak amplitude, the fraction of each cycle during which the diode conducts is a) One quarter of a cycle
b) One-third of a cycle
c) One half of the cycle
d) Three quarters of a cycle

Explanation: For one half of the cycle the diode conducts when 24 cos(Θ) = 12 or Θ is 600. Hence for a complete cycle the diode does not conducts for 2Θ or 1200. Hence the diode does not conducts for a third of a cycle.

4. Diodes can be used in the making of
a) Rectifiers
b) LED lamps
c) Logic gates
d) All of the mentioned

Explanation: Diodes are used to make rectifiers (full wave or half wave rectifiers are the most common examples), LED lamps uses diodes (diodes are generally doped for their use in this purpose) and logic gates can also be made using diodes using the fact that diodes are conducting only in the forward biased configuration.

5. For the connections shown below, the equivalent logic gate is a) OR gate
b) AND gate
c) XOR gate
d) NAND gate

Explanation: The following circuit behaves as a OR logic gate.
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6. For the connections shown below, the equivalent logic gate is a) OR gate
b) AND gate
c) XOR gate
d) NAND gate

Explanation: The circuit shown behaves as an AND logic gate.

7. The figure below shows a circuit for an AC voltmeter. It utilizes a moving-coil meter that gives a full-scale reading when the average current flowing through it is 1 mA. The moving-coil meter has a 50-Ω resistance. The value of R that results in the meter indicating a full-scale reading when the input sine-wave voltage VI is 20 V peak-to-peak is a) 3.183 kΩ
b) 3.133 kΩ
c) 3.183 Ω
d) 56.183 Ω

Explanation: Average value of input voltage= 20/π or 6.366 V.
Since there is diode half of the time there is no voltage across the voltmeter hence the average value of the input voltage is 10/π or 3.183V.
The total resistance required to generate 1mA current is 3.183 kΩ out of which 50Ω is provided by the moving coil. Therefore, a resistance of 3.133 kΩ is required.

8. The value of I and V for the circuit shown below are a) 2A and 5V respectively
b) -2A and 5V respectively
c) -2A and -5V respectively
d) 2A and 0V respectively

Explanation: I = V/R or 5/2.5 or 2A
For an ideal diode when it is conducting the potential drop across its terminal is zero.

9. The units frequently used to measure the forward bias and reverse bias current of a diode are
a) µA and µA respectively
b) µA and mA respectively
c) mA and µA respectively
d) mA and mA respectively

Explanation: The currents in forward bias is generally in MA and in the reverse bias it is very small and is generally measured in µA.

10. A diode
a) Is the simplest of the semiconductor devices
b) Has a characteristic that closely follows that of a switch
c) Is two terminal device
d) All of the mentioned

Explanation: Both the statements are true for a diode.

Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.

To practice all areas of Electronic Devices and Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers. 