I'm currently using the MP111 hybrid op-amp set up as a voltage controlled current source with a gain of 1. But what I'm finding is that at low input voltages the gain is much higher than it should be - up to 8 A/V. As we increase the input voltage the gain decreases sharply and then becomes 1.
Why is the gain so off at low input voltages? Is there a way to fix this?
I'm calculating the gain by dividing the current seen passing through the shunt resistor (Rs) by the input voltage.
MP111 datasheet: https://www.apexanalog.com/resources/products/mp111u.pdf
MP111 configuration as current source (figure 8): https://www.apexanalog.com/resources/appnotes/an07u.pdf
Rs = 0.01 Ohms, Rload = 0.05 Ohms, Rin = 101 kOhm, Rf = 1 kOhm.
The positive and negative rails are at +15V, -15V respectively. Boost functionality is not being used therefore Vboost pins are connected directly to the power rails.