Re: Choosing voltage opamp

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#2051

From: Johnny Boy
Date: Mon, 25 Sep 2006 09:39

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"David L. Jones" <altzone@gmail.com> wrote in message
news:1159082931.013808.167160@d34g2000cwd.googlegroups.com...
> Vitaliy wrote:
> > Hi David,
> >
> > Is the maximum Vp-p I can get from an opamp with +/-5V rails 5V then?
> > I know I measured the output of transimpedance amplifier and I was
> > getting maximum ~8Vp-p :confused:
>
> It depends on the particular device.
> As a general rule of thumb an opamp can get to within at least 2V of
> either rail, so a +/-5V supply will give you at a minimum +/-3V. Your
> opamp could aboviously get within 1V of the rail to give you 8Vp-p.
> There are "rail-to-rail" opamps that claim to get very close to the
> full output voltage rail, but usually not at any significant output
> current.
> You need a higher rail voltage regardless of the device you choose.
>
> Dave :)
>

You should listen to David, he knows what he's saying - even the very best
of rail-to-rail op-amps won't go close to the supply rails, except if
they're very lightly loaded, 1M etc. They still usually fall short of the
negative rail by 5-50mV and 0.5-1.5V short of the positive rail.
... Johnny

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Subject: Re: Choosing voltage opamp
Date: Mon, 25 Sep 2006 19:39:46 +1000
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