Temperature coefficient of Avalanche breakdown diodes is
A. Positive
B. Negative
C. Both
D. Depends

Hint: The temperature coefficient of Avalanche breakdown will tell us whether the breakdown voltage increases or decreases with temperature. We need to understand the basic working of Avalanche diodes to know the variation of the breakdown voltage with temperature.

Complete step by step answer:
When a diode is reverse biased, a very amount of current flows through the diode due to minority charge carriers. As we increase the reverse bias voltage, a point will come when the electron hole will break apart and move towards opposite electrodes. This is called breakdown of the diode as the depletion layer of the diode breaks apart with increase in reverse bias voltage.
There are two types of breakdowns possible based on how they are triggered. They are the Avalanche breakdown and the Zener breakdown.
Now in case of an Avalanche breakdown, the breakdown of the diode is triggered by the energetic electrons striking and breaking apart the electron hole pairs. As the temperature of the diode is increased, the energy of these electrons will increase but the mean free path for these electrons will decrease (just like in the case of resistance in metals) due to which we will need to apply more voltage to achieve the breakdown.
Therefore, based on the above discussion we can say that the temperature coefficient of Avalanche breakdown diodes is positive.

Hence, the correct answer is option A.

Note:
It should be noted that the behaviour of the Avalanche breakdown is opposite to that of the Zener breakdown. The temperature coefficient is negative in case of Zener breakdown where the Zener voltage decreases with increase in temperature.