From: Tony Williams
Subject: Re: Historical question: negative feedback and the op amp
Date: Fri, 15 Nov 2002 07:40:53 +0000 (GMT)
References: <firstname.lastname@example.org> <3DD24CD4.ECD230B9@webaccess.net> <email@example.com>
NNTP-Posting-Date: Fri, 15 Nov 2002 08:23:14 +0000 (UTC)
User-Agent: Pluto/1.14i (RISC-OS/3.60)
In article ,
Frank Miles wrote:
> In article <firstname.lastname@example.org>,
> Tony Williams wrote:
> > ..... He notes that Cin = Cf*(1+A), where A= gm*Rl.
> > Note the "apparently". I don't have Terman's 1943
> > book but have a 1950 Terman book, where he references
> > back to his 1943 book in the footnotes.
> Couldn't find any reference to sawtooth, ramp, or sweep
> generators either. No Cin formula either -- there's
> an equivalent circuit for a triode (without any
> acknowledgement for what we know today as the Miller effect).
> No similar equivalent is shown for the pentode.
Thanks for looking. In Terman's 1952 book, (note the
corrected date for the second edition), the footnote is
alongside the formula, referencing his 1943 REH page 467,
and a remark that Cf is large compared to the interelectrode
capacitances which are neglected in the formula. So perhaps
he was just referring to something basic about valves.
> There is a lot of amazing stuff on effects of grid design,
> electron optics in CRTs, and hosts of other stuff nobody
> but specialists deal with any more.
Since Terman was a prof it is probably a proper view
of what an electronics engineer needed to be armed
with 60 years ago..... the rate-of-change between
then and now is frightening isn't it.