Editing Linear regulator (section)

=== Series regulators ===
Series regulators are the more common form; they are more efficient than shunt designs. The series regulator works by providing a path from the supply voltage to the load through a variable resistance, usually a transistor (in this role it is usually termed the series '''pass transistor'''); it is in the "top half" of the voltage divider - the bottom half being the load. The power dissipated by the regulating device is equal to the power supply output current times the ''voltage drop'' in the regulating device. For efficiency and reduced stress on the pass transistor, designers try to minimize the voltage drop but not all circuits regulate well once the input (unregulated) voltage comes close to the required output voltage; those that do are termed '''low dropout''' regulators,  A series regulator can usually only source (supply) current, unlike shunt regulators.