PI-TYPE FILTERS use both capacitive and inductive filters connected in a pi-type configuration.
Because of the combination of filtering devices, the ability of the pi filter to remove ripple voltage is
superior to that of either the capacitance or inductance filter.
VOLTAGE REGULATORS are circuits designed to maintain the output of power supplies at a
constant amplitude despite variations of the ac source voltage or changes of the resistance of the load.
This is done by creating a voltage divider of a resistive element in the regulator and the resistance of the
load. Regulation is achieved by varying the resistance of the resistive element in the regulator.
A SERIES REGULATOR uses a variable resistance in series with the load. Regulation is achieved
by varying this resistance either to increase or decrease the voltage drop across the resistive element of
the regulator. Characteristically, the resistance of the variable resistance moves in the same direction as
the load. When the resistance of the load increases, the variable resistance of the regulator increases;
when load resistance decreases, the variable resistance of the regulator decreases.