I am in a need of a simple circuit for sweeping a voltage of a solar cell and measuring the current.

I started with a simple voltage regulator, such as this one: enter image description here

and adjusted it so it would work according to my purpose: ln

My colleague suggested to use closed loop compensation. But I am not sure how to approach that. Can I get some suggestions so the circuit will be stable ?

  • \$\begingroup\$ One difference is that in the upper schematic the reference is connected to the positive input terminal of the OpAmp and the feedback to the negative input terminal (yielding negative feedback). Apply this to the lower schematic as well. This might be a or the reason it doesn't work \$\endgroup\$ – Huisman Sep 16 '19 at 17:38
  • \$\begingroup\$ Could you tell more about the component that represents the solar cell? Is it a voltage source in your circuit (like the title suggests)? How did you implement that source? If it is an ideal* non-linear voltage source, the OpAmp / BJT will not regulate anything, but stay in steady state, \$\endgroup\$ – Huisman Sep 16 '19 at 17:42
  • \$\begingroup\$ the second schematic works ... in simulation. In practice, the circuit can be unstable. The solar cell model is realistic, reflecting all the nonlinearities as with normal solar cell (it is a single diode model, complete but basic one for describing solar cells) \$\endgroup\$ – Martin G Sep 17 '19 at 4:30
  • \$\begingroup\$ Did you try swapping the inputs of the OpAmp? The lower circuit now has a positive feedback which could lead to instability. \$\endgroup\$ – Huisman Sep 17 '19 at 12:08

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