ACTIVE AND PASSIVE COMPONENTS
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ACTIVE components increase the power of a signal and must be supplied with the signal and a source of power.

Examples are bipolar transistors, field effect transistors etc.

The signal is fed into one connection of the active device and the amplified version taken from another connection.
In a transistor, the signal can be applied to the base connection and the amplified version taken from the collector.

The source of power is usually a dc voltage from a battery or power supply.
 

PASSIVE components do not increase the power of a signal.
They often cause power to be lost.
Some can increase the voltage at the expense of current, so overall there is a loss of power.
Resistors, capacitors, inductors and diodes are examples of passive components.

Integrated circuits contain both active and passive components.
Since they usually increase the power of a signal and require a source of dc power they are treated as active devices.


Copyright Graham Knott 1999