Close the switch to start. Tweak the feedback resistors to get a different voltage drop.
A Constant Voltage Electronic Load is a test equipment that is used to test constant current sources, such as battery charger circuits and the CC function of a bench PSU. It senses the voltage at the input terminals and compares it against a reference and adjusts the resistance of the MOSFET in such a way that the voltage drop across it remains constant irrespective of the current draw.
The value of constant voltage is given by
Vconst = Vref*(1+R2/R1)
Putting Vref = 2.5V, R2 = 10k, R1 = 20k, we get Vconst = 3.75V, which is the nominal voltage of a lithium ion battery.
Constant Current Type: http://everycircuit.com/circuit/4538767357247488
Constant Resistance Type: http://everycircuit.com/circuit/5400474459832320
