Gate drive for Class C

[ka1tdq]

I'm almost finished with my CW transmitter for 20 meters, and I have a question about the schematic before I wrap it up.  I've planned it to be 23 watts out (a 50 ohm match for 48 vdc on the final mosfet), and I will be keying power to the mosfet driver.  The oscillator will remain on for transmit.

I'm wondering about what the waveform should look like going into the gate of the final.  I'm getting 150mV peak-peak from the oscillator which will go to the input of the driver.  I've put a voltage divider on the input with a variable 5k resistor so that I can adjust the output waveform.  I'm hoping 150mV is enough to vary the waveform.

I'm thinking that for class C, I need to adjust the 5k so that the final mosfet will conduct for about 30% of the time and not for 50/50 on/off.  Am I correct on that?

Jon
KA1TDQ

[ka1tdq]

I just got a private message about how to correct some issues. I need to add a class A buffer after the oscillator to get about 3 volts peak to peak in order to drive the input to the logic IC. Then, add an IXDD between the chip and the mosfet gate to get a good 12 volt swing. Thanks!

Jon
KA1TDQ