# Amplifier efficiency calculations?

1. Mar 7, 2012

### MehhShell

Would the efficiency calculated using the P output/P input x 100 get the same answer as calculating the efficiency using the RMS input and output values? If so why?

2. Mar 7, 2012

### vk6kro

No, it isn't the same.

Efficiency is the power out into a resistive load divided by the DC power into the amplifier, multiplied by 100 to get percentage.

The power into the resistive load is usually caused by an AC voltage across the load.

The power into the amplifier is the (DC supply voltage) times the (DC current) supplied to the transistors in the amplifier.

Last edited: Mar 7, 2012