Here is the circuit in question: https://www.circuitlab.com/circuit/nju7nfp5mvu3/constant-current-circuit/
The output current at the load (R4) is simulated to be a bipolar current, when it isn't possible for current to flow through the MOSFET in the reverse direction due to the unipolar source used (V3). Other simulators such as the Falstad siulator and LTSpice show a correct unipolar current as output.
See discussion here for more details, as well as an image of the simulation output: https://www.reddit.com/r/AskElectronics/comments/5uc1pc/why_does_a_spike_occur_in_the_current_when_it/
Is this an error in the parameters of the IRF1530 or in a way that it is being simulated?
February 17, 2017
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