what is common collector
The picture quality is not that great but here is a drawing of a self biased common collector BJT http://imageshack.us/photo/my-images/200/selfbiasedcommoncollect.png/
emitter follwer
current gain
The percentage of doping in emitter is higher than collector region.hence large current is flow to emitter than collector.
what is common collector
Common collector amplifier can be used as a voltage buffer and in impedance matching
A circuit in which the input signal is applied to its base and the collector is earthed (grounded) is known as common collector configuration of BJT (BiPolar Junction Transistor)
Common-emitter gives more voltage gain because a common-collector amplifier has a voltage gain of 1. But a common-collector can have a power gain because the input impedance is much more than the output impedance.
from the name itself the common collector has its collector terminal in common with both the input and output circuits of a transistor and the base current is chosen as the input current and the output current is the emitter current
unity
The picture quality is not that great but here is a drawing of a self biased common collector BJT http://imageshack.us/photo/my-images/200/selfbiasedcommoncollect.png/
220 ohm's
emitter follwer
current gain
No voltage gain
The common name is a Philatilist. This is a Greek in origin.