LTSpice simulation of uBitx Power Amp

Jerry Gaffke
 

I've uploaded an LTSpice simulation of the uBitx Power Amplifier from Q90 on out through the IRF510's
but not including any of the transmit low pass filters, can be found here:
    https://groups.io/g/BITX20/files/KE7ER/ubitx_pa.asc
A pdf of the LTSpice schematic is here:
    https://groups.io/g/BITX20/files/KE7ER/ubitx_pa.pdf

I ran several simulations, all with a 0.05 volt pk-to-pk sine wave driven into C80 at the base of Q90.
Anything much higher and there was some definite gain compression going on.

With the IRF510 gates clipped out of the circuit, I saw 7.7v p-p of drive for each gate at 30mhz, 10.0v p-p at 7mhz.
Note that these signals were still loaded by the 47ohm resistors at R97 and R98

With the gates restored and the IRF510's powered from 12v, the gates had 3.0v p-p at 30mhz, 8.0v p-p at 7mhz.
Simulated power out (computed from the unfiltered p-p voltage into 50 ohms) was 5W at 7mhz and 0.9W at 30mhz. 
  
Will be interesting to see what this does if the gates are driven harder.
Also interesting to try a simulation of the WA2EBY amp using the same IRF510 models.

Jerry, KE7ER

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