#### ansu_s

##### Junior Member level 3

**flowing current wastes power**

Hi, I don't quite understand why a Class-E Power Amplifier is efficient. See the attached Class-E diagram.

My understanding is that C1/L1 resonate at the switching frequency, so that the transistor drain is at zero volts when current is flowing, and C2/L2 filter out unwanted harmonics.

But for C1/L1, when current is flowing (with the drain at zero volts), current is flowing from the supply to ground. No power is dissipated in the transistor due to the zero-volt drain, but this energy still comes from the supply and doesn't go to the load - so surely this is wasted energy, and so lowers efficiency? I believe that the Class-E can be 100% efficient, but I guess I don't understand something because I don't see why...

Ansu