Q-point in a transistor

MrAl

Joined Jun 17, 2014
11,258
Hi,

It's called the Q point probably because the Q stands for "quiescent" which means the no input signal point. This is also called the bias point. This usually refers to the output bias point but you may want to know what the input is doing too.

The bias point helps establish the operating conditions for the circuit.
 

Thread Starter

AlwaysNumber1

Joined Dec 4, 2016
52
Hi,

It's called the Q point probably because the Q stands for "quiescent" which means the no input signal point. This is also called the bias point. This usually refers to the output bias point but you may want to know what the input is doing too.

The bias point helps establish the operating conditions for the circuit.
Can you please describe this in more details ?)
 

MrAl

Joined Jun 17, 2014
11,258
Hi again,

When you use a transistor in an amplifier circuit you have to bias it with resistors to get it to work properly. The output bias point is the point that the output assumes once it is biased. A typical example is where we have a 10 volt power supply and we use a resistor on the input of the transistor to bias the base emitter diode but look at the output collector to see if it is at the bias point we want, which is typically one half of Vcc. So with a 10 volt power supply we probably bias the transistor so the output is at 5 volts. That would be called the bias point or Q point. At that time there is no input signal other than the DC bias from the resistor.
 
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