Hii I have a low voltage signal arounf 0.1 to 2.0 mv I want to convert it to a current signal in the order of several mili-amps so that it is less influenced by noise in the circuit. Are there standard Op-Amps that can do this stuff ? The voltage source has almost zero driving capability. It is an output of a thermo-coupler. Let me know guys if you have any idea as to how to implement it.

 

Are there standard Op-Amps that can do this stuff ? Yes. Look for one with low and stable offset voltage. This is pretty low voltage for a thermocouple, the temp. must be low too. There may be better temp. sensors for your ( unknown ) application.

 

How about going digital?

http://www.sparkfun.com/datasheets/IC/MAX6675.pdf

If you must stay analog, here's some good stuff on I/E converters:

http://www.allaboutcircuits.com/worksheets/opamp7.html

Here's a T/C amplifier for J, K, (and maybe T) T/C's:

http://www.analog.com/static/imported-files/data_sheets/AD594_595.pdf

You can get quite a bit of gain from it so it should be pretty easy to feed into an E/I.

There are commercial T/C transmitters that provide a 4-20 ma output for whatever T/C you have, here's one:

http://www.newportus.com/ppt/TX93A_TX94A.html