Setting the Quiescent Point in an NPN Circuit

[sanado]

Hey guys, was just wondering if you could clear up some conflicting information i have found. In the v simply NPN transistor circuit, what is responsible for settings the quiscent point? Is it the voltage divider or Rc.

I no that the voltage divider ensures that the amplifier is 'switched on' while Rc ensures .5Vcc is added to output signal. Therefor, wouldn't Rc be ultimatly responsible for settings the quiescent point?

 

[kamerling]

If you have an emitter follower, the quiescent output voltage is always a diode drop below the output of the voltage divider.

With a common emitter amplifier the collector current is set by the voltage divider (and there will be an emitter resistance as well for successful biasing), but the voltage drop across Rc will be I_c * R_c. So the answer should be: all of them