Jim Lux wrote in
:

....
That is a new / unconventional definition of 'linear'.

The term is usually used in this context to mean a linear transfer
characteristic, ie PowerOut vs PowerIn is linear.

Or, as I used it, that superposition holds.
One can build an amplifier or other device where the Pout(Pin)
=straight line, but is not linear in the formal sense. Say you built a
widget that measured the input frequency and amplitude, then drove a
synthesizer at that frequency and amplitude = 2*input amplitude.


Yes Jim, I should have written Vout/Vin is linear, that Vout(Vin) has no
significant terms higher than first order.

Noting that a single ended Class B or AB amplifier can only be linear
when a resonant load or suitable filter is included as part of the
system.

Elsewhere it was suggested that I do not accept the 'flywheel'
explanation of the tank circuit. That is not true, but it is a limited
explanation, simple, and appealing, but limited.

Another explanation is to view the anode current waveform as containing a
DC component, a fundamental component and harmonic components and a
filter that adequately reduces the undesired components provides the
solution to a single ended Class B or AB linear amplifier. The filter is
not restricted to a resonant 'tank' circuit.

I have modelled the operating characteristics of my HF linear using 4
572B in AB2. An FFT of the anode current reveals the spectral content, it
is plotted at http://www.vk1od.net/lost/572BIaSpectrum.png . Of course,
the output filter must only select the fundamental component for linear
operation, selection of a harmonic would not be acceptable for a complex
input waveform because it would destroy the absolute relationship between
different frequency components of the input.

Owen