Adjust the pot to set the discharge current from 0 to 2A. The switch toggles between pulse mode and continuous discharge. The 3.7V supply represents a battery here. The caps are there to prevent EC errors with opamp closed loops. To measure the capacity, one would have to integrate the discharge current over time until the battery voltage drops below a specified level. You can also implement a constant load discharge by adjusting the reference voltage to meet R=Ubat/Id=const. The reference voltage is provided by a divider here, but it could be fed from DAc to make it fully automated. The bottom mosfet acts as an electronic load and operates in the ohmic region so it dissipates a lot of heat, use heatsink.
