[sdiy] Sequencer good (and bad) news update

[Ian Fritz]

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).
>
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