gEDA-user: Opamps et al...

[Peter Clifton <pcjc2@xxxxxxxxx>]

Hi,

I'm a little rusty at analog electronics, and was hoping someone might
be able to advise me..

I'm trying to make a little building block which houses an
instrumentation amplifier, input protection diodes, and a buffer amp to
drive a (say) 50 Ohm load.

My intention was to use an AD8230 precision zero drift instrumentation
amplifier (basically with the datasheet input circuit), then follow it
with an unity (or 2x) gain op-amp buffer to drive a cable. (Probably in
series with a 50 Ohm resistor (assuming a 50 Ohm load), however I may
opt just to drive low-impedance, since I'm working with low frequencies,
and transmission line effects to the 'scope or control circuit intended
won't be severe.

If I have an op-amp left over unused in a package, what is the
recommended way of tying its inputs to avoid noise / power consumption?
I figured connecting the inverting input to the O/P, then the
non-inverting input to GND. Perhaps I should just use the second op-amp
to drive a non 50Ohm output?

I was looking at LT1112 for the op-amp stage, (as I have one here),
although I might substitute a lower spec one later.

Are there any gotchas to watch out for when using opamps to buffer at
low gain?.. I can vaguely recall there being an issue with low gain and
some amps (depending on their internal compensation).

Thanks!

Peter Clifton




_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user