[sdiy] Equiv of LM3900?

[harry]

The big point here is "what did you want the opamp to do"...

The LM3900 has a very (like extremely) low input impedance.

Usually we select voltage input opamps to have a high impedance
input...

so for some circuits you 'might' sub another opamp... but if the designer

really understood the 3900... you probably can'r because the reasons for
that choice are almost incompatible with 'normal'  (not Norton ;^)
opamps.

H^) harry

Magnus Danielson wrote:

> From: mark verbos <a0284520 at addcom.de>
> Subject: Re: [sdiy] Equiv of LM3900?
> Date: Sat, 02 Mar 2002 19:58:17 +0100
>
> >
> >
> > Steve Ridley wrote:
> >
> > >
> > >The LM3900 (and the ones I've lsited above) are current difference
> > >opamps.  You can't just substitute any "normal" opamp.  (Actually
> > >you can, but then it won't work).
> > >
> > Ha. That's true about everything isn't it? ;)
>
> Indeed.... but to be even more correct it should say ", but then it
> won't work anything near as you migth expect from the original
> design".
>
> Ah well...
>
> Cheers,
> Magnus

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