Hi all,
I'm not too sure if I can explain the problem I am having clearly, but i'll give it a go.
In the schematic attached, I am using the voltage across resistor Rsense (0.1 Ohm) as an input to a PLC. Because the maximum current flowing through is 2A, even the maximum voltage drop across Rsense (0.2V) will not be enough to trigger the PLC input. As such, I have passed it through a non-inverting amplifier with a gain of 81.
When testing the circuit, I found that the output voltage of the opamp (LF412CN) is actually about 120 bigger than the input. This is the case even at smaller currents. I do not know what is causing this problem. I have a feeling it might be the capacitance or inductance in the circuit, but right now, I don't know how to fix it. Any help from you guys would be greatly appreciated.
Thanks.