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

 

[Moetasim]

The quiescent point, also known as the bias point, is the operating point of a transistor where there is no input signal and the output is at a stable, steady state. In an NPN transistor circuit, the quiescent point is typically set by both the voltage divider and Rc.

The voltage divider, consisting of resistors connected to the base and emitter of the transistor, helps to establish the base-emitter voltage and controls the current flow through the base. This is important because the base-emitter voltage directly affects the amount of current flowing through the transistor, which in turn affects the output signal.

Rc, or collector resistor, is responsible for setting the quiescent output voltage by adding a bias voltage to the output signal. This helps to ensure that the transistor operates within its linear region and does not saturate or cut off.

Therefore, both the voltage divider and Rc play important roles in setting the quiescent point in an NPN transistor circuit. It is important to carefully choose the values of these components to achieve the desired operating point and ensure stable operation of the circuit.