Shunt regulator serves as inexpensive op amp in power supplies.

This article discusses how a three-terminal shunt regulator can replace a more expensive conventional operational amplifier in a power-converter design. A switched-mode power supply uses a galvanically isolated feedback portion of a pulse-width modulation circuit. In designs that omit a voltage amplifier, a shunt regulator can serve as an in expensive operational amplifier. Resistors set the power supply's direct current output voltage, and optocoupler integrated circuit provides galvanic isolation.