[sdiy] Sequencer good (and bad) news update

[harry]

Hi Ian (et al)

Hmmm... My  application was used as a comparator... so I would
have expected it to work quite well near ground as well. I don't think
the 500mV was offset voltage ???

How light was your load ?   Mine was fairly heavy (like 2mA)

H^) harry

Ian Fritz wrote:

> Harry  et al. --
>
> I just finished my latest project (a MIDI wind controller) that does all
> sensor reading and conditioning with LM324's. It uses a total of 15
> amplifiers. I was easily able to get all the outputs to swing to within 7
> mV (worst case) of ground.  I run the circuits off a 6.4 V supply, which
> allows the outputs to swing up to 5.0 V for direct interfacing with PIC A/D
> inputs.
>
> I can't understand the discrepancy in our experiences. The only time I saw
> an off voltage above 10 mV was when two amplifiers were cascaded and the
> second unit amplified the small offset of the first one. This was easily
> taken care of by  feeding the second amplifier a compensating input
> bias.  I agree that large offsets can accumulate if you are not careful
> with the design.
>
>    Ian
>
> At 09:06 PM 4/17/2002, harry wrote:
> >Hi Ian....
> >
> >I'd say the LM324 goes to within a few hundred millivolts of ground
> >(normally)... like maybe 500mV. You can get lower outputs if you use a
> >pull-down
> >resistor. I got to maybe 200mV in a commercial design.
> >
> >The funny thing is... the "zero" supplied the device driving my circuit had
> >about
> >700mV of offset... guess what opamp they used (yup - 324)
> >
> >H^) harry
> >
> >Ian Fritz wrote:
> >
> > > My experience with the 324 is that it will swing to within a few mV of gnd,
> > > as specified. Have you had trouble with this?
> > >
> > > At 08:50 AM 4/17/2002, Tony Clark wrote:
> > >
> > > >   Most likely a LM324 is only going to put out something
> > > >like 1.2V-10.8V and an TL08x is more like 0.9V to 9.1V (or something
> > > >close to that).
> >
> >--
> >Jihad Terrorism Conspiracy New World Order
> >Revolution Black Helicopters Freedom of
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--
Jihad Terrorism Conspiracy New World Order
Revolution Black Helicopters Freedom of
Speech First Amendment Rights: Carnivore Bait
go ahead and READ my e-mail I have nothing to
hide... how about YOU ???