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Note: Close switch after starting simulation.
This circuit is essentially a voltage controlled current sink that is particularly useful in testing power supplies.
It consists of a current shunt resistor, in this case 0.001 ohm and a power transistor, the voltage dropped across the shunt will be I*R, this is sensed by an op-amp in a differential amplifier configuration, the resulting voltage being proportional to the current through the shunt resistor is fed to the inverting input of another op-amp.
This forms a control loop with the reference input such that it will drive the transistor to make the voltages equal, thus allowing current control, in this case 1mV per amp.
In practice there will be amplification of the feedback to reduce noise, improve accuracy and increase dynamic range, in addition for such high currents low Rds MOSFETs will be used in a parallel configuration as well as a proper current shunt amplifier.
Due to a problem with everycircuit I had to add a switch in the feedback path, it must be open when starting simulation.
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