emitter follower

[sandy92]

common collector configuration is called as emitter follower.therefore collector should be grounded, why emitter is grounded?how the voltage gain is unity?
**broken link removed**

 

[ericgibbs]

common collector configuration is called as emitter follower.therefore collector should be grounded, why emitter is grounded?how the voltage gain is unity?
**broken link removed**

hi sandy,
The collector is not grounded, its connected to the +Vrail, so its a 'common' collector, which is connected to 0V via the Vrail decoupling caps.

Regards the unity gain, consider how much negative feedback the emitter signal generates with respect to the base signal.

 

[Increazon]

This is right configuration. One word - collector needs resistor too and base need additional resistor - if you want to have temperature stability.

 

[JimB]

In an emitter follower, the collector is indeed connected to the +ve rail (assuming an NPN transistor), but, from a signal point of view the collector is at ground potential.

Not shown in the circuit in the OPs link, Vcc should be decoupled to the "ground" line with a capacitor which has a low reactance at the lowest frequency of interest.

Thus, Vcc is at signal ground potential, hence the collector is grounded at signal frequencies.

JimB