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Path: utzoo!mnetor!seismo!ll-xn!cit-vax!mangler
From: mangler@cit-vax.Caltech.Edu (System Mangler)
Newsgroups: comp.arch
Subject: Re: computer devices
Message-ID: <1335@cit-vax.Caltech.Edu>
Date: Fri, 12-Dec-86 11:39:47 EST
Article-I.D.: cit-vax.1335
Posted: Fri Dec 12 11:39:47 1986
Date-Received: Mon, 15-Dec-86 04:35:25 EST
References: <7396@utzoo.UUCP>
Organization: California Institute of Technology
Lines: 17
Summary: gain often not very high

In article <7396@utzoo.UUCP>, henry@utzoo.UUCP (Henry Spencer) writes:
> we need a high-gain amplifier device so that minor
> variations in gain won't matter.

Even in fairly well-behaved technologies like MOS, the gain is often
not very high.	In PMOS, which used enhancement-mode pullups, a gain
of -3 was considered good.  4-transistor dynamic RAMs amplify on the
same principle and have a tough time getting a gain of -1.5.  Even
CMOS may have gains as poor as -4 due to short-channel effects; it
gets worse at high supply voltages and small feature sizes.

Some forms of GaAs logic allow the pulldown transistor to conduct
quite a bit when it is nominally off (due to limitations on where
the threshold can be set), and these too have trouble getting much
gain.

Don Speck   speck@vlsi.caltech.edu  {seismo,rutgers,ames}!cit-vax!speck