Question

Plz answer it rapid i need your help.......
Why common emitter is known as impedance matching & Buffer amplifier?

Answer 1

The common collector amplifier, often called impedance matching since its output is taken from the emitter resistor, is useful as an impedance matching device.
Since its input impedance is much higher than its output impedance, it is also termed a "buffer" for this reason and is used in digital circuits with basic gates.

Answer 2

how it match the impedance ?

Answer 3

bcause amplification factor beta is usually ranges from 20-500 hence this configuration gives appericiable current gain as well as voltage gain at its output
on the other hand in the Common Collector configuration has very high input resistance(~750 kilo ohm) & very low output resistance(~25 ohm) so the voltage gain is always less than one & its most important application is for impedance matching for driving from low impedance load to high impedance source