Diode Power Loss
P = Vf × If
Quick answer
This calculator solves P = Vf × If for Power. With Forward Voltage 12 V, Forward Current 2 A, the result is 24 W. It solves in 3 directions, so you can enter the values you have and get the one you need.
Calculator
Formula
Description
A forward-biased diode drops a relatively constant voltage (Vf) regardless of current, so its power dissipation is simply the product of forward voltage and forward current. Silicon diodes typically drop 0.6-0.7V, Schottky diodes 0.2-0.45V, and LEDs 1.8-3.4V depending on color. In power supply rectification, diode losses can be significant: a 1A load through a silicon diode wastes 0.7W, while a Schottky diode wastes only 0.3W. This is why synchronous rectification using MOSFETs is preferred in high-efficiency power supplies.
Variables
- P — Power dissipation (W)
- Vf — Forward voltage drop (V)
- If — Forward current (A)
Practical Notes
For more accurate calculations at high currents, use the piecewise model: P = Vf0 × If + Rd × If², where Vf0 is the threshold voltage and Rd is the dynamic resistance. Schottky diodes have lower Vf but higher leakage current and lower maximum reverse voltage than silicon diodes.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| P | Power | W | µW, mW, W, kW |
| Vf | Forward Voltage | V | pV, nV, µV, mV, V, kV |
| If | Forward Current | A | pA, nA, µA, mA, A, kA |
Step by step
- 1. What you know: Forward Voltage 12 V, Forward Current 2 A
- 2. The relation: P = Vf × If
- 3. Substitute: Vf = 12 V, If = 2 A
- 4. Result: Power = 24 W
Related quantities from the same inputs
- P = V × I = 24 W
Worked examples
Minimum range
Given: Forward Voltage 0.33 V, Forward Current 2 mA
Result: Power = 0.66 mW
Low range
Given: Forward Voltage 3.3 V, Forward Current 20 mA
Result: Power = 66 mW
Typical
Given: Forward Voltage 12 V, Forward Current 2 A
Result: Power = 24 W
High range
Given: Forward Voltage 0.23 kV, Forward Current 100 A
Result: Power = 23 kW
Maximum range
Given: Forward Voltage 2.3 kV, Forward Current 1 kA
Result: Power = 2300 kW
Solving for each variable
Solve for Power
Forward Voltage 0.33 V, Forward Current 2 mA → 0.66 mW
Solve for Forward Voltage
Power 10 mW, Forward Current 2 mA → 5 V
Solve for Forward Current
Power 10 mW, Forward Voltage 0.33 V → 30.3 mA
How Power changes with Forward Voltage
| Forward Voltage (input) | Power (result) |
|---|---|
| 1.2 V | 2.4 W |
| 3 V | 6 W |
| 6 V | 12 W |
| 9 V | 18 W |
| 12 V | 24 W |
| 18 V | 36 W |
| 24 V | 48 W |
| 48 V | 96 W |
| 84 V | 0.168 kW |
| 120 V | 0.24 kW |
The same result in other units
| Unit | Value |
|---|---|
| mW | 24000 |
| W | 24 |
| kW | 0.024 |
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<p><a href="https://vbatpower.com/formulas/diode-loss/">Diode Power Loss</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Diode Power Loss?
Use P = Vf × If. With Forward Voltage 12 V, Forward Current 2 A, Power works out to 24 W.
What is the formula for Diode Power Loss?
The formula is P = Vf × If. A forward-biased diode drops a relatively constant voltage (Vf) regardless of current, so its power dissipation is simply the product of forward voltage and forward current.
How do you find Forward Voltage when you know the other values?
Rearrange for Forward Voltage: with Power 10 mW, Forward Current 2 mA, Forward Voltage is 5 V.
How do you find Forward Current when you know the other values?
Rearrange for Forward Current: with Power 10 mW, Forward Voltage 0.33 V, Forward Current is 30.3 mA.
What units does Diode Power Loss use?
Power is shown in mW, W, kW. Values are held in SI base units internally, so you can mix prefixes without converting by hand.
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