The Automatic Voltage Regulator (AVR) is a device designed to regulate voltage automatically that is, to take a fluctuating voltage level and turn it into a constant voltage level.

A Voltage Regulator is an electronic circuit that provides a stable DC Voltage independent of the load current, temperature and AC line voltage variations. A voltage regulator may use a simple feed-forward design or may include negative feedback. It may use an Electromechanical Mechanism, or Electronic Components. Depending on the design, it may be used to regulate one or more AC or DC Voltages.

The circuit consists of following four parts.

• Reference voltage circuit
• Error amplifier
• Series pass transistor
• Feedback network