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Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
References: <email@example.com> <firstname.lastname@example.org>
Subject: Re: Opamp GBW tempco ?
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X-Inktomi-Trace: public1-pete2-5-cust19.pete.broadband.ntl.com 1031762259 22002 18.104.22.168 (11 Sep 2002 16:37:39 GMT)
Date: Wed, 11 Sep 2002 17:37:39 +0100
NNTP-Posting-Date: Wed, 11 Sep 2002 17:37:39 BST
"fred bartoli" wrote in message
> Kevin Aylward a écrit dans le message :
> > "fred bartoli" wrote in message
> > news:email@example.com...
> > > Maybe a question for Kevin or Jim ?
> > >
> > > For my 100kHz IF amplifier that has to have a really (really mean
> > <0.01d)
> > > stable phase rotation at the (constant) IF frequency, I'm
> > the
> > > sensitivity of all the components.
> > > One point I don't have answer is the tempco of opamps.
> > > The ones that I want to use are in the 100/200MHZ range, bipolar
> > (low
> > > voltage noise).
> > >
> > > Any order of magnitude for this tempco ?
> > If the data sheet don't spec it, I reckon you have to bank on 20% to
> > or so at least as an open loop gain variation over temperature. Some
> > might be better, it depends on how well all the gm stages have been
> > biased with a PTAT current.
> That is about 0.2% to 0.5% per °C and is pretty large regarding my
> that means that I probably will have to measure it and account for in
> amplifier, and the situation may not be so bad if this tempco is
> Do you have some ideas about that ?
It might take a bit of digging. Off hand, I have not looked much at
temperature variations of the Early effect.
Note that the GBW is also highly variable from unit to unit. e.g. a 741
might be quoted at typically 1Mhz, but it might be 0.47MHz to 1.5Mhz.
The open loop dc gain might easily be a vary by factor of two.
The whole idea of the high open loop gain is that on closed loop the
variations are reduced tremendously.
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
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