Bipolar Junction Transistor Part 2

Sources

Stabilizes the fixed bias configuration by adding : it makes the transistor’s DC currents and voltages closer even when the temperature and varies.
The capacitor voltage is constant, so in DC analysis, it is treated as an open circuit to isolate the AC signals.
Formulas
Get the outer loop formula through KVL (Counter clockwise, following the flow of the current)
when at saturation region
and when at cut-off region
quiescent operating point midway = 1/2 of quiescent.
1/5 of emitter base resistance means 1/5 of emitter because the emitter was said first.

In a fixed bias configuration and a emitter stabilized configuration, and is dependent on .
- Because is temperature sensitive, a temperature increase will change and .
A voltage divider bias circuit is nearly independent of , thus solving the problems introduced by it.
- Even if changes when changes, the operating point defined by and remains constant as long as the appropriate parameter is utilized.

TIP

and are the output current and voltage.

The quiescent point is the point wherein the transistor operates at its most optimal state.

Two methods of analyzing this bias circuit:

Some Included Components

TIP

Unlike fixed-bias, it has

Unlike emitter-stabilized, it has

Although it does not seem obvious, the two base resistors are parallel to each other. Their combination is , while their combined voltage is .

Then use methods/formulas similar to the ones in the previous biases (emitter stabilized and fixed) to solve for the other values.

In order to use this method, the following conditions must be satisfied:

When this conditions are satisfied, it implies that the is almost 0; therefore, we can replace it with an open circuit. Hence

The additional node will result in two currents flowing through it (e.g., and ).