I need to convert a small DC current into voltage. One of the ways is to use an opamp circuit often called transimpedance amplifier. The problem is that (1) the current I need top sense is always positive, (2) transimpedance amp is inverting (Vout = -Rf * Iin the feedback is negative) and (3) I don’t have a negative supply rail. On the positive side, my OpAmp has Rail-to-Rail (RR) inputs and outputs.
I want to connect the positive input of the OpAmp to the positive +5V supply instead of ground (see the circuit diagram below). I think that the output then will be Vout = Vcc - Rf * Iin > 0 for my range of input currents. Do you think that this can work?
It is not very smart.
There are some current sense IC at Maxim.
Essentialy boath inputs are on the side of sense resistor. There are some application notes. look there.
It is not very smart.
There are some current sense IC at Maxim.
Essentialy boath inputs are on the side of sense resistor. There are some application notes. look there.
You're probably right. I'm getting the same result from the similation with LTspice. The output is equal to the supply rail all the time no matter what the input current is.
Do you have any ideas or sugestions about how to make a precision single-supply current sensor that would work in the nanoamp range?