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.....