Avalanche breakdown occurs at a reverse bias voltage of
Right Answer is:
With an increasing reverse bias voltage, the electric field across the junction of a p-n diode increases. At a certain reverse bias, the electric field imparts sufficiently high energy to a thermally generated carrier crossing the junction. This carrier, on colliding with a crystal ion on its way, disrupts a covalent bond and produces a new electron-hole pair. These carriers can also gain sufficient energy from the applied field and collide with other crystal ions to generate further electron-hole pairs. The process is cumulative and produces an avalanche of carriers in a very short time. Avalanche breakdown is sometimes called Impact breakdown.
- Consequently, the avalanche breakdown voltage (which is higher than 6 V) increases with a rise in temperature.
- The reverse bias voltage applied is relatively higher of the order of 8 – 10 V depending upon doping.
- Thus the temperature coeﬁicient of the avalanche breakdown voltage is positive. The change of the breakdown voltage is about 0.1 percent per centigrade degree change of the diode temperature.