current sense (transimpedance, IVC) OpAmp

[kender]

max471 ltspice

Colleagues,

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?

Thanks,
Nick

P.S.
This post is loosely related to this one

Here's a 3D animation (!) of the transimpedance amplifier https://engineering.dartmouth.edu/3Dcircuits/animations/currentamp.html

Obviously, this circuit can be easily prototyped and experimented with. But at the moment I have to do a “paper design”.

 

[Robert Qi]

current sense op amp

It doesn't work, I think!
Because the operational point of the opamp is not correct. Vp>Vn, so vout=5 always!

 

[servicemann]

resistor transimpedance op amp

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.

 

[kender]

negative transimpedance

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.

Are you talking about the chips like MAX471 and MAX472 (or their more recent derivatives)?

EDIT after about 36 hours: Well, smart ass, are you at all capable of saying somethis specific? I've solved my problem, so now I'm just curious.

Added after 3 minutes:

It doesn't work, I think!
Because the operational point of the opamp is not correct. Vp>Vn, so vout=5 always!

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?