Diode Forward Voltage Calculator
Estimate typical forward voltage and conduction power for silicon, Schottky, germanium, and common LED technologies at a selected current.
Choose a reference diode type or enter a custom Vf from a datasheet curve or measurement. Results support early component selection, voltage-budget checks, and thermal estimates.
Typical values are deliberately approximate. Verify minimum, typical, and maximum Vf at the intended current and junction temperature before completing a hardware design.
Engineering tool
Diode Forward Voltage Calculator
Estimate typical forward voltage and conduction power for common PN, Schottky, germanium, and LED diode technologies.
Select a typical reference or enter a custom operating-point Vf.
Current through the diode at the evaluated operating point.
Typical forward voltage
700 mV
Silicon diode
Result console
- Typical forward voltage
- 700mV
- Forward current
- 20mA
- Power dissipation
- 14mW
Diode Type Notes
Common PN-junction reference value at moderate current.
Engineering Recommendation
Verify reverse voltage, recovery behavior, surge current, and Vf at the intended current.
Diode Forward Voltage Reference
| Diode Type | Typical Forward Voltage | Typical Use | Notes |
|---|---|---|---|
| Silicon diode | 0.7 V | General rectification and protection | Common PN-junction reference value at moderate current. |
| Schottky diode | 0.3 V | Low-voltage rectification and switching | Low forward drop and fast switching, usually with higher leakage. |
| Germanium diode | 0.3 V | Low-level detection and vintage circuits | Low forward drop with higher leakage and limited modern availability. |
| Red LED | 2 V | Indicators and displays | Typical Vf for common red indicator LEDs at nominal current. |
| Green LED | 2.2 V | Indicators and status lighting | Technology-dependent; modern green LED Vf can vary substantially. |
| Blue LED | 3.2 V | Indicators and illumination | Typical InGaN blue LED reference at nominal operating current. |
| White LED | 3.2 V | Indicators and lighting | Usually a phosphor-converted blue LED with similar electrical behavior. |
Formula reference
Forward Voltage and Power
Forward voltage is selected from a typical technology reference or supplied by the user. Power is estimated for steady forward conduction.
Power dissipation: P = Vf × IfVariable definitions
- Vf
- Forward voltage in volts
- If
- Forward current in amperes
- P
- Conduction power in watts
Worked Example
Silicon Diode at 20 mA
If = 20 mA = 0.02 A; typical Vf = 0.7 V
P = 0.7 × 0.02 = 0.014 W = 14 mW
Use the exact diode datasheet curve to refine Vf and power at the expected temperature.
Engineering Notes
Operating point matters
Forward voltage depends on current, temperature, diode technology, and device construction.
Schottky trade-offs
Schottky diodes usually have lower forward voltage but higher reverse leakage.
Silicon is widely used
Silicon PN diodes are common for general rectification, switching, and protection.
LED material sets Vf
LED forward voltage depends strongly on color, semiconductor material, current, and bin.
Use datasheet curves
Always verify forward voltage at the intended current and junction temperature.
Support reference
FAQ
What is diode forward voltage?
Forward voltage is the voltage measured across a conducting diode at a specified current and temperature. It depends on semiconductor technology, device geometry, current, and junction temperature.
What is the typical forward voltage of a silicon diode?
A common engineering reference is about 0.7 V, but real silicon diode Vf can be lower or higher depending on current, temperature, device type, and package.
Why do Schottky diodes have lower forward voltage?
A Schottky diode uses a metal-semiconductor barrier rather than a PN junction, commonly producing lower forward drop and little minority-carrier reverse recovery.
Why do LEDs have different forward voltages?
LED color comes from semiconductor bandgap and material composition. Higher-energy blue and white-emitter junctions generally require more forward voltage than red emitters.
Does diode forward voltage change with current?
Yes. Forward voltage rises logarithmically with current in the ideal model and is also affected by series resistance and self-heating. Always use datasheet curves at the intended operating point.
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Reference voltages are nominal examples, not guaranteed component limits. Verify the selected diode datasheet, test conditions, temperature range, tolerances, reverse ratings, surge limits, and thermal design.