On Thu, 12 Jul 2007 12:18:59 -0700, Frank Gilliland
wrote:

+++On Thu, 12 Jul 2007 17:39:01 GMT, james wrote
+++in :
+++
+++On Thu, 12 Jul 2007 05:23:51 +0100, " Peter"
+++wrote:
+++
++++++With pure amplification, the signal may have altered in amplitude,
++++++but a sinusoidal waveform will still be a sinusoidal waveform on
++++++the output. The sine, angular frequency and phase shift are
++++++all unchanged.
+++*************
+++
+++Wrong
+++
+++Depending on how the amplifier is configured there is a phase shift.
+++In a Common emmiter configured transistor amp there is a 180 degree
+++shift in the pahse. So the waveform is altered by phase.
+++
+++Only the emitter(source) follower in a semiconductor amplifier will
+++not cause a phase shift.
+++
+++Correct that the angular frequency is not changed and that a sine wave
+++is a sine wave, but still the amplitude has changed. Therefore they
+++are not identical weaveforms. Therefore they do change, if only in
+++amplitude.
+++
+++
+++I think the key word here is 'waveform', where 'form' is the issue and
+++scale or phase are not. Because ANY device, active or passive, will
+++introduce some phase delay and amplitude variation to the signal. So
+++be practical or be a purist, but you're both really just saying the
+++same thing.
+++
+++Now if you wanted to take this to a philosophical level, no two
+++signals can EVER be identical for the simple reason that they can
+++always be differentiated, if not by amplitude or phase then by
+++temporal location (one is the input, the other is the output) or by
+++physical location (you measure this one here and that one there). But
+++by the same rule of identity I guess that means no two opinions will
+++ever be identical either, so argue away.....
+++
*********

In a way this could be considered nit picking. I agree that the
overall form is a sinusoid. I just don't like the implication that all
sinusiods are unchanged by amplification, positve or negative. Granted
the amplitude of the form is alterd and little on none of the rest of
the function is not. Yet the amplitude is a partt of a sinusoidal
waveform.

again it is a minor point.

james