# Temperature Effects

PN junction diode parameters like reverse saturation current, bias current, reverse breakdown voltage and barrier voltage are dependent on temperature. Rise in temperature generates more electron-hole pairs thus conductivity increases and thus there is an increase in current.

Increase in reverse saturation current with temperature offsets the effect of rise in temperature. Reverse saturation current (IS) of diode increases with increase in temperature the rise if 7% per Celsius for both germanium and silicon and approximately doubles for every 10 degree Celsius rise in temperature.

Thus, if the voltage is kept constant as temperature is increased, the current increases. Carrier voltage is also dependent on temperature as it decreases 2.5mV per degree Celsius for germanium and silicon. Reverse breakdown voltage (VR) also increases as we increase the temperature.

## Ideal and Practical Diode Characteristics

Ideal Diode : When an ideal diode is in forward bias, it offers no resistance and acts as an open switch. Likewise, the ideal diode under reverse bias offers infinite resistance and hence acts like an open switch.

Practical Diode : A diode which is said to be forward biased it starts conducting at knee voltage and under reverse bias no current due to majority charges hence a practical diode is considered to be an open switch(minority charge current ignored)

Threshold Voltage : Ideal diodes do not have a threshold voltage. Once any forward voltage is applied across the diode, it will conduct instantly across its junctions.

Forward Current : Ideal diodes include unlimited forward current when any forward voltage is applied across the terminals. This is due to the ideal condition; the inner resistance of the diode would be 0.

The ideal diode would have no internal resistance at all since current(I=V/R) is equal to voltage.

Breakdown voltage : Ideal diodes do not have breakdown voltage. This is because, the diode has unlimited resistance to reverse voltage. It will not perform any current at all when voltage is applied in reverse.

Reverse (leakage) Current : As an ideal diode does not contain a breakdown end, it never performs and reverse current termed leakage current. It is an ideal insulator when voltage is applied in reverse.

Peak Inverse Voltage : Also known as Maximum Reverse Voltage, it is the max allowable reverse operating voltage that can be applied across the diode without reverse breakdown and damaging occurring to the device.

Total Power Dissipation : It is the maximum possible power dissipation of the diode when it is forward biased.