Hello, friends.

I'd like develop a small device to switch on a relay (or maybe a semiconductor switch like a SCR or TRIAC) on passing a current as low as 0,2 uA in another circuit with return by the ground. In this circuit the thevenin impedance to source is 10-12 Mohms.

I thinked to use a trasresistante amplifier with output of 2,5 volts or more.

Do you know any IC fitted to it?

 

Many existing Op Amps and comparators can
do that. Nearly all the recent ones. There
are also Norton amps which operate on
current, but the GP types can easily deal with
these impedances.

Regards
cww