Question

Distinguish between avalanche and zener breakdown.

Answer 1

1. Avalanche Breakdown: 

• It occurs in junctions which are lightly and have wide depletion widths. 
• It occurs at higher reverse voltages when thermally generated electrons get enough kinetic energy to produce more electrons by collision. 
• At reverse voltage above 6 V breakdown is due to avalanche effect. Electric field produced is weak in nature. Charge carriers obtain energy from the applied potential. 

2. Zener Breakdown: 

• It occurs in junctions which are heavily doped and have narrow depletion widths. It occurs due to rupture of covalent bonds by strong electric fields set up in depletion region by the reverse voltage. 
• At reverse voltage below 6V breakdown is due to zener effect. 
• A strong electric field is produced 
• Zener current is independent of applied voltage.