I built this small circuit to test if the op amp is working; or if I understand how they should work.
I don't have a bench power supply so I take the 7 voltage that I have, I used a resistor divider to create 1 volt max; around 900mV and send that into the op amp's inverting input. I ground the non-inverting input.
I also run the +7 volt to the v+ of the op amp chip and v- is set to ground.
I tried switching the inverting and non inverting wires as well while using a multimeter to measure the output pin and ground.
I am getting 32mV from the output.
The op amp is OPA2604; dual op amps in one package.
Do I need resistors or something on this op amp? How come I am getting a max of 32mV at the output and zero if I switch the inverting/ non-inverting inputs?
simulate this circuit – Schematic created using CircuitLab
Best Answer
That won't work. As soon as the inverting input goes higher than the non-inverting input the output is driven as far negative as it can go. This will be close to 0 V as you found out.
simulate this circuit – Schematic created using CircuitLab
Figure 1. Reconfiguration as a voltage follower.
Figure 2. Extract from the datasheet.
You need a better power supply for your purposes. Two 9 V batteries would do.