[Amps] Need Help build Nonlinear Amplifier

[jeff millar]

cm215 at greenwich.ac.uk wrote:

>Hiya Chaps,
>
>I am trying to build a non linear amplifier for a pre distorter amplifier 
>however I need help on how to build a non linear amplifier that uses MOSFET's.
>  
>
...not sure I understand you're question. These articles shows the block 
diagram
for classic analog pre-distort.
http://doi.wiley.com/10.1002/mop.11292
http://www.highfrequencyelectronics.com/Archives/Apr04/HFE0404_Stapleton.pdf

Analog linear predistortion works by adding a waveform to the input that
compensates for the compression of the amplifier. The added waveform
generally comes from a diode clipping circuit that simulates the main
amplifier at low level signals. Then additional circuits determine
the difference between input and compressed signals and add the
difference back into the input which cancels the distortion and improves
IMD performance.

These circuits require matching the compression curve of the amplifier
and the amplitude and phase of the correction signals. In addition, the
amplifier may have varying distortion characteristics due to recent power
history such as temperature, power supply sag, etc. that affect
the distortion.

jeff, wa1hco