Require help

[nitskulkarni]

I want to convert a dc voltage signal to current signal using opamp
My requirements are as follows

I/P 90 TO 120V DC
O/P 4 to 20 mA DC

 

[Willbe]

I/P 90 TO 120V DC to a 20x resistive attenuator giving 4.5 to 6 V,
then
level shift by -4.125 V with an adjustable bandgap reference giving 0.375 to 1.875 V,
then
have the opamp give a transconductance of (20-4)/(1.875 to 0.375) = 10.7 millimhos, giving 4 to 20 mA.

Unless
your source can deliver sizeable amounts of current, and
unless
you need the 20 mA with the 90 V in.

 

[Hero999]

What exactly are you trying to do?

It could be possible that you're trying to do something the wrong way.

 

[nitskulkarni]

I am trying to build control system for a transformer the i/p of transformer is 90-120V i want to take this range sample it and test if the ip goes out of it

 

[Hero999]

Transformers don't work on DC, they require AC.