Hi everyone,

I need to read phase voltage which is around 220V and I have choosen ratio as 1/300 for opamp. After that I will read this value in mcu.
But I have no idea about that how to find capacitor value that between inverting and non inverting input. In some design, 440pF and 15pF was found.
Can anybody help me about that ?

 

Be really careful working directly connected to the mains!
I'm not sure that the cap value is very critical. Split the difference and try 220pF .

 

You might want to do a spice sim with Tina TI to look at phase
margin, stability, for cap of choice.

Or just proto the circuit, pick a C value, and feed a square wave
into one input, and examine if there is any serious ringing on LMV324
output.

http://www.ti.com/lit/an/slva381b/slva381b.pdf

Regards, Dana.

 

But I have no idea about that how to find capacitor value that between inverting and non inverting input. In some design, 440pF and 15pF was found.
Can anybody help me about that ?

Why is that capacitor there at all? In that position in the circuit, it will not filter out any noise and it will degrade the stability of the circuit (i.e., will make it tend to oscillate). Remove it.