Hello!
I'm trying to create a simple current sensor using OpAmp as shown in the following schematic: http://tinyurl.com/y43jfjky
It all works as expected in simulation, but when I wire it up using real components, the OpAmp behaves strangely.
My real circuit has the same setup as in the simulation...
- The current through 0.1 ohm resistor is 22mA.
- Voltage on IN+ pin is 2.2 mV
- pot values are exactly as in the schematic
However, my real Opamp Always outputs around 4V, which causes IN- pin voltage to be around 400 mV.
Shouldn't the OpAmp lower the output voltage so IN+ and IN- match?
This is the OpAmp I'm using: RC4558P
This is an image of how I wired the circuit on the perfboard (the one with parralel copper lines)
(I scratched the 4 copper leads behind the OpAmp and one above the ground pin of the potentiometer.)
I had the same circuit on the breadboard yesterday and it was working (roughly). I was getting very strange values because my breadboard has couple of ohms of contact resistance, which completely screwed my measuremens. I was hoping to get better accuracy using perfboard, but now the OpAmp doesn't seem to work, and I'm not sure of anything any more
Does this look like a malfunctioning OpAmp to you?
Is it possible that I burned the OpAmp while soldering?
Thank you.
I'm trying to create a simple current sensor using OpAmp as shown in the following schematic: http://tinyurl.com/y43jfjky
It all works as expected in simulation, but when I wire it up using real components, the OpAmp behaves strangely.
My real circuit has the same setup as in the simulation...
- The current through 0.1 ohm resistor is 22mA.
- Voltage on IN+ pin is 2.2 mV
- pot values are exactly as in the schematic
However, my real Opamp Always outputs around 4V, which causes IN- pin voltage to be around 400 mV.
Shouldn't the OpAmp lower the output voltage so IN+ and IN- match?
This is the OpAmp I'm using: RC4558P
This is an image of how I wired the circuit on the perfboard (the one with parralel copper lines)
(I scratched the 4 copper leads behind the OpAmp and one above the ground pin of the potentiometer.)
I had the same circuit on the breadboard yesterday and it was working (roughly). I was getting very strange values because my breadboard has couple of ohms of contact resistance, which completely screwed my measuremens. I was hoping to get better accuracy using perfboard, but now the OpAmp doesn't seem to work, and I'm not sure of anything any more
Does this look like a malfunctioning OpAmp to you?
Is it possible that I burned the OpAmp while soldering?
Thank you.