TI XTR110 have a selectable output 4-20mA, 0-20mA (your need) and other.
Put 0V at input you get 0mA, put 5V at input you get 20mA.
Only a P-channel PowerMos and a couple of resistors.

Marcelo Y.

>Well for analog output we use MAX5122 and derative which fulfills our
>needs :)
>but I was asking for 20mA current loop transmitter/reciever circuit, it
>different
>as it is for transmitting only 2 levels of 'data' (on/off) and are used
>for communications
>over longer distances, quite common in the industry, well nowdays there
>are more and more
>RS422/485 but 20mA still have its share.
>A 20mA curent loop can carry communication +1000 meters at fairly low
>baudrates,
>this in 'heavy' industries i.e. 10 V/m immunity etc.
>It's pretty basic design wise, but selectable active/passive complicates
>it somewhat, anyway
>it was  a *long* time ago i dweeled into these circuits and thought
>there could be
>some new chips or similar that could simplify things for me ( i.e small
>footprint, small
>number of componets etc ).
>
>
>/Tony
>
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