Suggestions for low voltage opamps

[dan4oto]

Hi,
i need to measure current in circuit with a 3.3V microcontroller(pic24 series).
My question is: what op amp have I to use. Now I'm using LM358, but the simulation in TINA-TI shows, that max output voltage from OA is les than 2 V.
And what should i prefer: differential ampl (high side measurment), or low side measurement with non-inverting amplifier?
The circuit:

 

[SeungminLee]

Low voltage op amps

You are going measure voltage difference beside R6 and calculate the current. is it right?
I think you should use instrument amplifier. differential amplifier has relatively low input Z that can affect input Z of system. many instrument amplifers have adjustable gain option that will suit for your work.

 

[dan4oto]

Re: Low voltage op amps

Maybe a have to make my question more concrete: The solution has to be simple The main problem is the non-linearity near to supply voltage and ground. Also the range of measurement: 20mA-500mA or (*0,1ohm) 0.2mV-5mV.
With others words: how can I achieve wider measurement range by higher gain, keeping high linearity, and that all using simple and cheep IC

 

[keith1200rs]

Low voltage op amps

I guess the easy solution is a chip designed for the job:

**broken link removed**

There are plenty of alternative high side current sense chips around. Otherwise, you need an instrumentation amplifier, or at least an opamp with very low offset.

Keith.

 

[karesz]

Low voltage op amps

Hi,
I thiktoo, that a dedicated IC is the best solution...
As OP it must have not only ( low offset, but it must be a RRIO type too!
K.

 

[dan4oto]

Re: Low voltage op amps

**broken link removed**

It seems to be a very good solution.

Thank you, Keith!