| Voltage in (Vin) | V | |
| Forward Voltage (Vf) | V | |
| Forward Current (lf) | mA | |
| Voltage source too low, must be higher than LED forward voltage | ||
| Resistor | Ω | |
| Power | W |
Example
We have an LED with a forward voltage of 2V which requires 20mA (0.02A)
A 9V battery
What size resistor is required?
Answer: 350 Ohm
