Input/Output Voltage Class C RF Amp

Discussion in 'The Projects Forum' started by dccircuit, Dec 16, 2015.

  1. dccircuit

    Thread Starter New Member

    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.
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    Actually, the PI net on the output, C45, L7,... RFC1 is specifically chosen not to store energy...
  3. dccircuit

    Thread Starter New Member

    Aug 3, 2014
    Thanks Mike--can you explain how that is working?
  4. SLK001

    Senior Member

    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.