Common collector configuration in BJT

[Vasantha Kumar R]

Why output impedance in common collector configuration of BJT is low?
Output impedance for both Common collector and common emitter configuration is measured across collector and emitter terminal then why there is difference in value. for common emitter terminal output impedance is high but for commom collector configuration output impedance is low.
please help me...

 

[barry]

Not quite right. Output impedance of common collector (emitter follower) is measured between the emitter and common, not emitter to collector. The output impedance of the common collector is approximately equal to the source resistance divided by the current gain (hfe).