Question

What are the possible temperature effects on the forward and reverse-bias currents in a p-n junction? Explain clearly.

Answer 1

1. PN junction diode parameters like reverse saturation current, bias current, reverse breakdown voltage and barrier voltage are dependent on temperature.

2. Mathematically diode current is given by I=IS∗(exp((V/(n∗k∗T/q)))-1). Hence from equation we conclude that the current should decrease with increase in temperature but exactly opposite occurs there are two reasons:

3. Rise in temperature generates more electron-hole pair thus conductivity increases and thus increase in current

4. Increase in reverse saturation current with temperature offsets the effect of rise in temperature

5. Reverse saturation current (IS) of diode increases with increase in the temperature the rise is 7%/ºC for both germanium and silicon and approximately doubles for every 10ºC rise in temperature.