Input/Output Voltage Class C RF Amp

Thread Starter


Joined Aug 3, 2014
Hi all:

I am a new member here with my first post. I am an adult learner trying to self-teach RF electronics. I have been working through David Rutledge's Electronics of Radio, while building the NorCal 40A transceiver.
I am getting caught up on understanding the Class C RF power amplifier circuit.

I don't understand how the output voltage across the collector of Q7 can be more than twice the DC supply voltage (12VDC). I assume that the reactive components--such as RFC1--are storing energy?

Any help would be appreciated. I have included the schematic.


Joined Nov 29, 2011
You could have an inphase reflection that will double the peak to peak voltage at the collector. The 43V zener diode is a last ditch effort to protect the power transistor from Vce breakdown failure. Your output capacitors also need a breakdown voltage at least 4 times the static DC voltages.

Also, this post should be in the Radio and Communications section of the forum.