I have constructed the circuit shown in the figure which is class C amplifier for 27MHz transmitter, and is working as expected.

I have no problem matching the amplifier output to the load, the help I need is to match the amplifier input to the signal source (the signal source has 50 Ohm output impedance), I just need a way to get an approximate value of class C amplifier input impedance, or a simple method to measure it, or even a rule of thump is adequate, to design the input matching network.

Thanks in advance for any help

 

Hi froten,
Welcome to AAC.
Please post your asc circuit file.
E

 

Easiest way is a 50 Ohm resistor from input to ground feeding a high impedance input.

 

Hi froten,
This is one method of measuring Zin and Zout of the C class amp Vin & Vout.
E

 

Hi froten,
This is one method of measuring Zin and Zout of the C class amp Vin & Vout.
E
View attachment 323829

Thanks eric for your reply. I'm aware of this method but I think it is not applicable for non linear circuits, if you check collector current in AC analysis you find it far from real value, I found it about 0.4 ma in LTspice simulation under .ac analysis.

 

This looks like a power amplifier intended for CB radio use, and for an AM signal a class C amplifier will not be suitable to provide a useful output, other than jamming a frequency band. Because of the drive requirements, a class C amplifier is not useful for an AM signal.