A galvanostat (also known as amperostat) is a control and measuring device capable of keeping the current through an electrolytic cell in coulometric titrations constant, disregarding changes in the load itself.
Its main feature is its nearly "infinite" (i.e. extremely high in respect to common loads) internal resistance.
The designation "galvanostat" is mainly used in electrochemistry: this device differs from common constant current sources by its ability to supply and measure a wide range of currents (from picoamperes to amperes) of both polarities.
The simpler galvanostat consists of a high-voltage source producing a constant voltage
as follows This simple realization requires rather high voltages (~100 V) to keep the load current constant with sufficient approximation for all practical purposes.
Therefore, more complex versions of galvanostats, using electronic amplifiers with feedback and lower voltages, have been developed and produced.