[EFM] What EFM designs can be run from +9 volt supply?

[Harry Bissell]

Hi Rene (et al)

I don't think this will work... the input impedance is probably way too low.
OK for that transformer driven amp, but for a filter readout I'm not so sure.
The LM3900 inputs look kind of like a diode drop (hey... maybe 2...) to the
negative rail. Even with a blocking cap that would be really low...

If you tossed a couple of buffers in (maybe a fet follower...) it would
probably
work...

Just MHO....

H^) harry

René Schmitz wrote:

> Hi Marjan et al.
>
> Take a look at the GIF (from National Semiconductor AN-72 Section 3.7) it
> describes a line receiving amp which could be used for the balanced to
> single-ended conversion. The ratio of R1 and R5 sets the DC level at the
> output to Vcc/2. The gain is the same as in Toms circuit, so this will fit
> the bill. You don't need the x-former and Rline of course.
>
> Bye,
>  René
>
> At 17:54 15.07.00 +0200, >>>marjan<<< wrote:
> >BTW, while talking singlesupply vcf6, any advice how to use one opamp
> >from lm3900
> >norton in place of normal opamp in there? I have a design with one opamp
> >from 3900
> >left unused and I want to make it vcf6, it runs off 2 9V batterys.
> >opamp in vcf6 is standard diff amp, from one tap of ladder goes 100K and
> >10n in series
> >to - in of opamp. from other ladder tap goes 10n cap to + input and from
> >it 100K res
> >to vcc/2 (speaking of single supply version), and 1M res in opamp
> >feedback.
> >Now, how to change it to acommodate lm3900?
> >
> >thanks,
> >
> >marjan
> >
>
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