What is Zener breakdown and avalanche breakdown ?

Q: Zener and avalanche breakdown.

Ans :  Breakdown due to breaking of covalent bond of depletion layer termed as zener breakdown (After the discovery, C. zener) and such a diode is zener diode.

Zener diodes with different breakdown voltages (for regulations of different voltages) can obtained by changing the doping concentration of its p-and n-sides.

There is another variant of zener like breakdown if there is low doping concentration as compare than zener diode. Such diodes will have relatively wider junction widths. At very high reverses bias, already existing electrons and holes are accelerated in the junction field and may undergo many collisions (like nuclear chain reaction) with the atom in the crystal.

These new electron-hole pairs created atoms by impact ionization also get accelerated in the junction field and collide further with the crystal atoms giving an increasing number of new electrons and holes. These bias beyond a certain critical value. This phenomenon is known as Avalanche breakdown and the device is referred to as Avalanche diode.

Zener breakdown occur in heavily doped semiconductor where depletion layer is thin avalanche breakdown occurs in lightly doped semiconductor.

The amplifiers X,Y and Z are connected in series. If the voltage gains of X, Y and Z are 10, 20 and 30, respectively and the input signal is 1 mV peak value , then what is the output voltage (peak value)

Q: The amplifiers X,Y and Z are connected in series. If the voltage gains of X, Y and Z are 10, 20 and 30, respectively and the input signal is 1 mV peak value , then what is the output voltage (peak value)

(a) if DC supply voltage is 10 V ?

(b) if DC supply voltage is 5 V ?

The breakdown in a reverse biased p-n junction is more likely to occur due to

Q: The breakdown in a reverse biased p-n junction is more likely to occur due to

(a) large velocity of the minority charge carriers if the doping concentration is small

(b) large velocity of the minority charged carriers if the doping concentration is large

(c) strong electric field in a depletion region if the doping concentration is small

(d) strong electric field in the depletion region if the doping concentration is large

Ans: (a) & (d)

Figure given below shows that transfer characteristics of a base biased CE transistor. Which of the following statements are true ?

Q: Figure given below shows that transfer characteristics of a base biased CE transistor. Which of the following statements are true ?

Numerical

(a) At Vi = 0.4 V, transistor is in active state

(b) At Vi = 1 V, it can be used as an amplifier

(c) At Vi = 0.5 V, it can be used as a switch turned off

(d) At Vi = 2.5 V, can be used as a switch turned on

Ans: (b), (c) & (d)