NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/rec/audio/15459

Internet Message Format | 1992-11-20 | 1.9 KB

Path: sparky!uunet!zaphod.mps.ohio-state.edu!caen!uflorida!mlb.semi.harris.com!batman!gmc
From: gmc@linear (Great Cthulu)
Newsgroups: rec.audio
Subject: Re: PNP vs NPN Output Stages

     There is a lot more than simply carrier mobility that determines transistor
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Date: 13 Nov 92 21:12:31 GMT
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performance. There are a number of degrees of freedom available to the
designer. For example, there is diffusion resistivity of the collector, base,
and emitter areas. There is the profile of the diffusion as you get farther
away from the surface; is it Gaussian, linear, step, etc. There is the
relative depth of the diffusions determining the location and profile
of the base region. There is also the very significant parameter of
the area of the diffused regions, and the shapes, and the locations.
For example, the transistor can have a square emitter for maximum area and
minimum collector resistance or a long skinny rectangular emitter for
minimum base resistance. It can have the base region contact on one side
of the emitter, or two sides and have half the base resistance. I can
continue on. The point is, though that one cannot state that a device sounds
better simply because it is a PNP or an NPN. There are a large number of
parameters that determine a transistor's performance. Carrier mobility is
only one, and can be compensated for by the others. Anyway, most amps
nowadays have op amps in them, and both PNP's and NPN's will be in the
signal path regardless of the output stage.


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Cthulu Lives

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