[sDIY] CV output buffer chip?

[harry bissell]

A trick you can use with the LM324 is to put a stiff pull down resistor from
the output to ground. This will drag the output pin closer to ground when the
output is low, vs. the higher losses in this resistor at higher output
voltages. Once you get away from ground there is more current available to
drive the output, so you can get some benefit from this. Expect to get to
within 250-300mV of ground this way.

Watch out the LM324 does not have symmetrical source and sink capability. This
can cause funny problems if you drive a capacitive load.  :^) Harry Bissell

Stewart Pye wrote:

> Hi Toby,
>
> The CA3260 should do the trick, If you can get hold of it. There may be a
> more modern op amp but this is the only one I could find in the "IC Op Amp
> Cookbook" ( W.G. Jung.) It is a dual version of the 3160, which is an
> internally compensated version of the 3130. The CMOS output stage allows
> rail to rail output. It should fit all your requirements.
>
> If you find this part is hard to come by or too expensive, you could
> consider using a >5V supply and an LM324 quad op amp that will go close to
> ground but not Vcc. You don't even really need a regulator for it if you
> are penny pinching. They only cost $1 anyway. A similar dual unit is the LM
> 358 ( I think :)
>
> Regards,
> Stewart Pye
>
> At 11:37 PM 22/06/99 -0700, Toby Paddock wrote:
> >I'm (slowly) working on a CV controller and am looking for a
> >buffer op-amp for the output.  Can anyone recommend a chip?
> >Here is my shopping list...
> >
> >Need:
> >Operate on single 5v supply.
> >Enough current to drive several CV inputs on
> >things like minimoog, odyssey, sh-101, arp seq.
> >
> >Really hoping for:
> >Output goes to within about 0.5v of the rails.
> >
> >Would like:
> >Not surface mount.
> >Easy to get and semi-cheap.
> >Dual or quad.
> >
> >Not too concerned with:
> >Offset.
> >Frequency response.
> >Input impedance.
> >High gain.
> >
> >I'm finding that I have the op-amp skills of a breadstick.
> >It seems that the combination of single 5v supply and
> >output going nearly to rails is the killer.
> >
> > - -- -  Toby Paddock
> >http://www.seanet.com/~tpaddock
> >