In a physical diode, there is a component of the reverse saturation current due to leakage over the surface. The reverse saturation current increases approximately 7 percent/°C for both silicon and germanium. The relationship between T and V in V-I characteristics:

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UPSC ESE (Prelims) Electronics and Telecommunication Engineering 19 Feb 2023 Official Paper
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  1. T increases and V decreases
  2. V decreases and T increases
  3. T and V both increase
  4. T and V both decrease

Answer (Detailed Solution Below)

Option 4 : T and V both decrease
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Temperature (T) and Reverse Saturation Current (ls):

  • As temperature increases, the thermal energy promotes the generation of electron-hole pairs in the semiconductor material of the diode.
  • This results in an increase in the reverse saturation current(ls) with rising temperature. The increase is typically around 7-10% per degree Celsius for silicon diodes.

Voltage Drop Across the Diode(V):

  • The voltage drop across a diode, known as the forward voltage (Vf) or simply V in the V-I characteristics, tends to decrease with increasing temperature.
  • This is due to the higher reverse saturation current causing a more significant flow of charge carries, leading to a reduced voltage drop across the diode.
  • As temperature (T) increases, reverse saturation current(ls) increases.
  • Due to the higher ls, the voltage drop across the diode (V) tends to decease.

Here, option 4 is correct.

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