How Does A Potentiostatic Circuit Work?

I still have some doubts about the correct working of a potentiostat circuit, because in some cases it is determined that the amplifier responsible for controlling the potential between the working and the reference electrode and force the current flow between the electrode auxiliary and working electrode, operates in the inverter mode. However, in other explanations, it is said that this amplifier operates in the voltage adder configuration and that the feedback loop would be implemented by the resistance of the solution. What would be the correct explanation about the operation of a potentiostat circuit for an electrochemical cell of 3 electrodes?