Hi Kelly,

I made an analog output circuit that I used in a commercial product
a few years ago. It's simple, cheap and works well. Uses one
LM358 dual opamp, a few resistors, one cap, and 4 jumpers to
select some common voltage and current ranges. Input may be 0-
5V analog or a 0-5V PWM.

Sketched circuit in .GIF format is about 13k, emailed to you
directly. This topic comes up often, so if enough other people were
interested and didn't mind the bandwidth perhaps I could post it to
the list.

Kelly Schauf wrote:
> To the forum:
>
> I am looking at a simple 4-20mA transmitter circuit that I need for an
> industrial application.  Preferably, I am looking to do it with some form
> of op-amp based circuitry. It is important to state at this time that the
> Burr-Brown and Datel special purpose 4-20mA ICs have been ruled out due
> to their expense.
>
> Any help given would be appreciated.
>
> Thank you,
>
> Kelly Schauf
>

Brent Brown
Electronic Design Solutions
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Hamilton, New Zealand
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eMail:  brent.brown@clear.net.nz