[sdiy] Opamp that gets close to the rails?

David Cornutt cornutt at hiwaay.net
Wed Nov 26 02:13:50 CET 2003


I'm trying to build a simple voltage summing circuit, so I can
jack up the output of my MIDI/CV converter to feed to my EML 101.
Among the 101's perversities is the fact that the keyboard uses
an offset control voltage; the left edge of the keyboard is not
0V but 5V.  The right edge is about 9.8V.

I would like to power this circuit off of the 101's +-10V output
which is available on the panel, because it's convenient to
do it that way.  Is there an opamp that can get its outputs
to within 0.2V of the supply rails?  I vaguely recall seeing a
thread on this recently, but it doesn't seem to have made it
to the archive yet.  I'm currently trying to use a TL082 and
it goes non-linear at 7.1V with +-9V supply in a unity-gain
circuit with reasonable resistor values.

If there isn't, I can power it using a +-15V supply, but that
means the box won't fit where I want to put it, so it would be
nice if I could use the EML's 10V outputs.



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