voltage regulators

A voltage regulator is a device that is designed to maintain a constant voltage. Voltage regulators can take many forms, from a resistor and diode in series, to a component designed specifically for the job.

These voltage regulators are active components. A disadvantage is that they are less efficient than a switched supply.

The regulator’s resistance varies in accordance with the input voltage and the load, resulting in a constant voltage. The regulating circuit varies its resistance, continuously adjusting a voltage divider network to maintain a constant output voltage. The difference between the input and regulated voltages is dissipated as waste heat.

Switching regulators maintain their output voltage by switching on and off. The regulated voltage of a linear regulator must always be lower than input voltage, which means that the efficiency is limited and the input voltage must be high enough to always allow the active device to reduce the voltage by some amount.

With linear regulators, the regulating device is placed either in parallel with the load (shunt regulator) or between the source and the regulated load (a series regulator). Simple linear regulators may only contain as little as a Zener diode and a series resistor; more complicated regulators can include extra stages.

Despite their name, linear regulators are non-linear circuits because they contain non-linear components and because the output voltage is ideally constant (and a circuit with a constant output that does not depend on its input is a non-linear circuit).