Objective
I am trying to build a gain-of-1 current controlled current source (current mirror) that is less sensitive to resistor value variation. The designs i have been making are highly resister dependent, as I am using shunt resisters.
Specifications
- On the input and output sides, I have 24vdc source
- The input side control current is well behaved.
- Input and output safe-operating-range must include 4mA-20mA
- The load is 500 ohms
Current Approach
This is the circuit I have been playing with. The circuit is very dependent on the 50 ohm resisters.
I have looked at a current mirror, but the matched mosfets I can get only have a VDS of 10V, when given a 24vdc supply, bad things can happen.
Best Answer
Traditionally you would want to use an instrumentation amp of some kind.
Here's a circuit that uses a ZXCT1009 instead. Accuracy is up to the 4.7 / 47 ohm resistor matching and the ZXCT's transconductance accuracy, about 1%.