Diode Vf vs Temperature

Vf(T) = Vf_ref − 0.002 × ΔT

Quick answer

This calculator solves Vf(T) = Vf_ref − 0.002 × ΔT for Vf at Temp. With Vf Reference 1.32 V, Temperature Change 50 °C, the result is 1.22 V.

Calculator

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.

Symbols and units

Symbol Meaning Default unit Accepted units
Vf Vf at Temp mV pV, nV, µV, mV, V, kV
Vf_ref Vf Reference mV pV, nV, µV, mV, V, kV
dT Temperature Change °C °C

Step by step

  1. 1. What you know: Vf Reference 1.32 V, Temperature Change 50 °C
  2. 2. The relation: Vf(T) = Vf_ref − 0.002 × ΔT
  3. 3. Substitute: Vf_ref = 1.32 V, dT = 50 °C
  4. 4. Result: Vf at Temp = 1.22 V

Worked examples

Minimum range

Given: Vf Reference 22 mV, Temperature Change 2.5 °C

Result: Vf at Temp = 17 mV

Low range

Given: Vf Reference 0.22 V, Temperature Change 25 °C

Result: Vf at Temp = 0.17 V

Typical

Given: Vf Reference 1.32 V, Temperature Change 50 °C

Result: Vf at Temp = 1.22 V

High range

Given: Vf Reference 1.98 V, Temperature Change 85 °C

Result: Vf at Temp = 1.81 V

Maximum range

Given: Vf Reference 19.8 V, Temperature Change 850 °C

Result: Vf at Temp = 18.1 V

How Vf at Temp changes with Vf Reference

Vf Reference (input) Vf at Temp (result)
132 mV 32 mV
0.33 V 0.23 V
0.66 V 0.56 V
0.99 V 0.89 V
1.32 V 1.22 V
1.98 V 1.88 V
2.64 V 2.54 V
5.28 V 5.18 V
9.24 V 9.14 V
13.2 V 13.1 V

The same result in other units

Unit Value
µV 1220000
mV 1220
V 1.22
kV 0.00122

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Frequently asked questions

How do you calculate Diode Vf vs Temperature?

Use Vf(T) = Vf_ref − 0.002 × ΔT. With Vf Reference 1.32 V, Temperature Change 50 °C, Vf at Temp works out to 1.22 V.

What is the formula for Diode Vf vs Temperature?

The formula is Vf(T) = Vf_ref − 0.002 × ΔT. Like BJTs, silicon diode forward voltage decreases approximately 2 mV per degree Celsius.

What units does Diode Vf vs Temperature use?

Vf at Temp is shown in µV, mV, V, kV. Values are held in SI base units internally, so you can mix prefixes without converting by hand.

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