Re: Why are "engineers" so poorly educated?


"robert casey"

Let's see, I graduated Syracuse University in 1978 with a BSEE, so I'd be
an engineer.

** That makes you a graduate of a uni engineering course.

An " engineer " is someone professionally engaged in that class of work,
who may or may not be a graduate of a related uni course.



For class A, I'd add the condition "if the input signal level doesn't
drive the amp into distortion or clipping" to "_all_ the output
device(s)never cease conducting under any signal condition.". I also
added "all" to make it clear that each and every output device never turns
off.


** Or more simply, " while reproducing a sine wave at its output ".


I've seen class A amps that had push-pull tubes, each tube configured to
never shut off, thru out the entire waveform cycle.

** Often, that condition is load impedance dependant.


Okay, how about class AB? That's usually a push pull configuration

** Only usually??


where, at or near zero crossing, both devices are conducting.

** Or more simply, some degree of class A operation exists.


But get above, say 10% of maximum input signal level, one of the devices
stops conducting, and the other device is doing the work.


** More correctly - above some power level, one device will stop
conducting during part of each cycle.


Lets also say that this is a 100W amplifier, if you run it with an input
signal that makes only 1 watt (the volume control is set low), then, sure
you could call it a 1 watt class A amp. But that'd be rather silly...


** But if you made the load impedance 10 times higher than nominal, it
becomes class A throughout a sine wave cycle.

( One tenth the current can supply ten times the load impedance to the same
voltage.)

It is all very simple - really.



........ Phil


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