I've been trying to make a active load that would use a very small resistor, around 10mOhm as a shunt resistor. I've figured out how to make it, it's a common circuit, however since I need to use opamps to measure the voltage drop and drive the mosfet, I do require a negative voltage power source. I've tried simulating the circuit in the picture below in LTspice.
However while it seems to work ok when powering one opamp, when powering the mosfet driving opamp and the opamp connected to the shunt to amplify the voltage drop to the volt range, it seems to not be capable of generating a negative voltage anymore and goes into the +V range. Basically even though I thought opamp power rails don't really use any power, it seems the current draw is enough for the circuit to not be able to produce the negative voltage. Aka the load is too large.
I want to know if it's perhaps a LTspice problem, am I just not using the proper opamps (OP07) or is there a way for me to limit the negative supply current into the opamps. Or perhaps something else is drawing current that I'm not aware of. Here is a picture of the circuit I'm talking about. The graph shows the output of the "negative" voltage power source shown at the bottom left side.