Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
References: <email@example.com> <%Bfk9.477$DY4.firstname.lastname@example.org>
Subject: Re: Current Feedback Amp Questions
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Date: Wed, 25 Sep 2002 21:02:11 +0100
NNTP-Posting-Date: Wed, 25 Sep 2002 21:02:36 BST
"Walter Harley" wrote in message
> "Kevin Aylward" wrote in message
> > Ahmmm.. Current feedback explicitly addresses the problem of opamps
> > running at low closed loop gains. For a given internal compensation
> > capacitor, and simlular ft limits, CFB *usually* *more* stable at
> > gains.
> I'm sorry, Kevin is as usual quite correct. My confusion was that
> apparently a common mistake made by newcomers to CFB amps, of assuming
> the way to get a non-inverting unity gain buffer is to connect the
> the inverting input, just as you would for VFB. This unity-gain
> configuration is unstable for CFB amps; you need a feedback resistor
> So, not a problem with CFB amps at low gains; rather, a problem with
> non-CFB-experienced designers at unity gain. Again, my apologies.
There are some misconceptions with CFA though, e.g.
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.