1. The cut-in voltage decreases as the temperature increases. The diode conducts at smaller voltage at large temperature.

2. The reverse saturation current increases as temperature increases.

This increases in reverse current I

where I

_{o}is such that it doubles at every 10^{o}C rise in temperature. Mathematically,where I

_{o2}= Reverse current at T_{2 }^{o}C
I

_{o1}= Reverse current at T_{1 }C
ΔT = (T

_{2 }- T_{1})
3. The voltage equivalent of temperature V

_{T }also increases as temperature increases.
4. The reverse breakdown voltage increases as temperature increases.

__1.1 Effect pf Temperature on power dissipation__

To avoid the overheating and damage of the device, the maximum safe value of power dissipation is mentioned in the datasheet of the diode. It is (P

_{D})

_{max}. This is specified at normal room temperature of 25

^{o}C.

At higher temperature, as the device junction temperature is higher, it
can dissipate less power. Thus maximum power dissipation of the device
must be derated at high temperatures.

The Fig. 2 shows power derating graph for a particular device. Upto 25

Using this factor, new power P

where ΔT = T

^{o}C, it is rated for (P_{D})_{max }of 80 mW but at higher temperatures it is derated as it ca not dissipate same amount of maximum power. For a given temperature, (P_{D})_{max}value can be directly obtained from the graph. Many a times, a derating factor is provided in the datasheet of the device.Using this factor, new power P

_{2}at new temperature T_{2 }can be obtained from initial temperature T_{1 }as,Fig. 2 Power derated at high temperature |

where ΔT = T

_{2 }- T_{1}= Temperature rise
Once the new power is known, as V

_{f }is almost constant, new forward current I_{f }can be obtained.__1.2 Effect of Temperature on Forward Voltage Drop__

Most of the times, the drop across the diode is assumed constant. But
in few situations, it is necessary to consider the effect of temperature
on forward voltage drop.

It is seen that cut-in voltage decreases as temperature increases.

**Note**:The diode forward voltage drop decrease as temperature increases.

The rate at which it increases is - 2.3 mV/

This is shown in Fig. 3.^{o}C for silicon while - 2.12 mV/^{o}C for germanium. The negative sign shows decrease in forward voltage drop as temperature increases.Fig. 3 Effect of temperature on forward voltage drop |

The coefficient ΔV

_{f}/^{o}C is called voltage/temperature coefficient of diode. Knowing this and V_{f1 }at T_{1}, any V_{f2 }at T_{2 }can be obtained as,__1.3 Effect of Temperature on Dynamic Resistance__

where k = Boltzman's constant and T in

^{o}K constant.

The value 26 mV is temperature dependent and the above equation is applicable only at 25

^{o}C.

For higher temperatures, it gets changed as,

where T

**'**is new temperature in

^{o}K.

The above equation can be expressed as,

**Note**: As temperature increases, V

_{T }increase hence dynamic forward resistance increases.

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