What is a Linear Regulator?
Working Principle: A linear regulator operates by using a voltage-controlled current source to force a fixed voltage at its output. The control circuit continuously monitors (senses) the output voltage and adjusts the current source (according to the load's demand) to maintain the output voltage at the desired value.
Current Limit: The design limits of the current source define the maximum load current the regulator can supply while still maintaining voltage regulation.
Feedback & Stability: The output voltage is controlled via a feedback loop, which requires a certain type of compensation to ensure loop stability. Most linear regulators have built-in compensation circuitry, allowing them to remain fully stable without requiring external components.
External Components: Some regulators (such as Low-Dropout types) do require an external capacitor connected between the output pin and ground to ensure regulator stability.
Linear Regulator Operation
Voltage feedback is responsible for sampling the output. Resistors R1 and R2, which set the feedback ratio, can be either internal or external to the regulator.
The feedback signal is used to control the current passed by the series (pass) transistor to the load.
Linear Regulator Topology
