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:
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.
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
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.