LM358 Difference Amplifier Problem

[Taban]

Hi all,

First of all i have to thank you for this site, i am student at electrical and electronical engineering, and theese days i am studying on a battery management system(bms). But i have a problem with lm358. i cant measure the range voltage truly. My circuit screen shot:

View attachment 68394

Help please

 

[MikeMl]

For this circuit to work properly, you will need a negative power supply connected to pin 4 of the opamp. The correct output is -4.2V, so a negative supply is needed. To make the circuit work, you must match all four 10K resistors to better than 1%, 0.1% would be better. Also, the LM358 is a crappy amp to use for this circuit. Look at the effect of the input bias currents in my LTSpice simulation, below.

View attachment 68395

 

[Taban]

it works, thank you