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Re: [Amps] Linearization problem

Subject: Re: [Amps] Linearization problem
From: Steve Thompson <>
Date: Thu, 04 Dec 2014 22:40:15 +0000
List-post: <">>
And a bonus question: Do you think that the phase distortion in
such a class-A-AB-C-E amplifier will be bad enough to still
cause poor IMD performance, even while the envelope linearity
is excellent?

Yes. Around 1980 I prototyped an amplifier aimed at improving efficiency in a military hf manpack. The output stage was a wideband push pull affair which behaved like class B at low drive levels, moving towards class D at full output. A 'polar loop' (Petrovic and Gosling, Bath University) applied amplitude feedback via the PA bias supply and phase feedback via the synth PLL. With either not connected, the output spectrum was very wide - as best I remember, both loop bandwidths needed to be some 10's kHz to get acceptable results.

Later the design evolved to use 'cartesian loop' feedback with I/Q channels which are commonplace in modern systems but I think it got shelved. System integration onto chips needed to develop another decade or so to make it a practical alternative in that environment.

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