Question

A p-n junction diode can be used as

• A. condenser
• B. regulator
• C. amplifier
• D. rectifier

Answer 1

The correct option is D

rectifier

The explanation for the correct option

Option $\left(D\right)$-

1. As a p-n junction diode conducts in forwarding bias and does not conduct in reverse bias, thus unidirectional property leads to the application of diode in rectifiers.
2. The P-N junction is a rectifier diode because it has asymmetric current/voltage characteristics, allowing the current to flow in only one direction.
3. An example is the conversion of an alternating current into a direct current.
4. Figure shows the I-V characteristic for a silicon P-N junction.

The explanation for the incorrect option

Option $\left(A\right)$-

1. A p-n junction diode can not be used as a condenser. As a p - n junction diode conducts in forward bias and does not conduct in reverse bias (current is practically zero).

Option $\left(B\right)$-

1. In a voltage regulator, a Zener-diode is used. It is a highly doped p-n junction which is not damaged by high reverse current, it can operate continuously, without being damaged in the region of reverse background voltage and it cannot possible with the p-n junction diode.

Option $\left(C\right)$-

1. In an amplifier, a transistor is used. A p-n junction diode is basically a passive network element.
2. That is, it cannot generate power instead it dissipates it unlike active elements for example thyristors, Op-Amps.
3. In case of tunnel diode, the diode can be used as an amplifier but only in the negative resistance region i.e when voltage decreases with increase of current. In the negative resistance region a tunnel diode acts as a active device; and can be used as a relaxation oscillator or a voltage amplifier.

Hence, option D is the correct answer.