ELECTRONICS 1- Important Questions

 Chapter 1- Semiconductor 

Q.What is doping?

Answer: The process of adding impurities to the intrinsic semiconductors is called as "Doping". It helps in increasing the conductivity of pure(Intrinsic) Semiconductors.

Q. Explain formation of P-N junction diode ?

Answer: P-N junction diode is formed in following way:

1) The p-type and n-type semiconductors are joint together.

2) After formation of p-n junction, electrons from n-side and holes from p-side diffuse through the junction to the other side.

Q. What do you mean by potential barrier in PN junction?

Answer: The electric field that is created near the P-N junction due to presence of immobile positive and negative ions on both sides of junction, is known as barrier potential or cut in voltage. It is measured in volts.

Q. Draw and Explain the V-I characteristics of a P-N junction diode.

Answer: The V-I characteristics can be divided into two parts:

1) Forward Characteristics                 2) Reverse Characteristics

1. Forward Characteristics: 

1) In the beginning, forward voltage (Vf) is less than Cut in voltage, so forward current flowing through it is very small.

2) As forward voltage equals to cut in voltage, the current starts increasing rapidly.

2. Reverse Characteristics

1) In the beginning, the reverse saturation current remain constant if temperature is constant. 

2) As reverse voltage equals to breakdown voltage, the current starts increasing rapidly due to reverse breakdown.

Q. What is zener diode? 

Answer:  A zener diode, also known as a breakdown diode is a semiconductor device that is designed to operate in reverse direction when a certain specified voltage is reached.

Q. Draw the symbols.

Chapter 2- Bipolar Junction Transistor 

Q.Draw the PNP and NPN transistor.

Answer: 

1) PNP Transistors:-

2) NPN Transistors:-

Q. Explain α and β and obtain the relation between them.

Answer:  

Q.How transistor can be used as switch.

Answer: 

1. Transistor as open switch.

- We need to operate it in the cut off region. Where Vin=0 volts.

2. Transistor as closed switch.

- We need to operate it in saturation region. Where Vin is positive.

Q.Explain the construction of NPN and PNP transistor?

Answer: 

Construction of n-p-n: Made of "p" type semiconductor between two "n" type semiconductors.

Construction of p-n-p: Made of "n" type semiconductor between two "p" type semiconductors.

1) The emitter region is heavily doped.

2) The base region is thin and lightly doped.

3) The collector region area is slightly larger than emitter one's.