Diode Vf vs Temperature

Vf(T) = Vf_ref − 0.002 × ΔT

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Result
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Formula

Vf(T) = Vf_ref − 0.002 × ΔT

Description

Like BJTs, silicon diode forward voltage decreases approximately 2 mV per degree Celsius. This negative temperature coefficient means that as a diode heats up, it drops less voltage and conducts more easily at the same bias voltage. For diodes in parallel, this creates a positive feedback that can cause current hogging where one diode takes most of the current, heats up further, and eventually fails. This is why diodes are rarely paralleled for current sharing without individual ballast resistors.

Variables

  • Vf — Forward voltage at operating temperature (V)
  • Vf_ref — Forward voltage at reference temperature (V)
  • ΔT — Temperature change from reference (°C)

Practical Notes

Schottky diodes have a smaller temperature coefficient than silicon PN diodes. LEDs have a smaller Vf tempco of about -1 to -2 mV/°C depending on the material. This temperature dependence affects accuracy in precision rectifier circuits and must be compensated in clamping circuits that set precise voltage limits.

Related Formulas

MOSFET Conduction Loss MOSFET Switching Loss BJT Total Dissipation Diode Power Loss Zener Regulation Resistor Transistor Current Gain (β)

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