**Base Bias Circuit With Collector and Emitter Feedback:**

In this Base Bias Circuit With Collector and Emitter Feedback circuit, as obvious from its name, both collector and emitter feedbacks are used in an attempt to reduce circuit sensitivity to changes in β. Increase in β causes increase in emitter voltage but decreases collector voltage. As a result voltage across base resistor R_{B} is reduced causing I_{B} to fall thereby partially compensating the increase in β.

In this Base Bias Circuit With Collector and Emitter Feedback circuit a current flows in resistance R_{C} from the supply V_{CC}. At point A this current divides itself in two parts, one flowing in the collector of transistor, l_{C} and the second part flows in the base resistor R_{B}, I_{B}. Thus current flowing in resistor R_{C} will be equal to I_{B} + I_{C}.

No current flows to the output terminals since coupling capacitor C_{C} offers infinite impedance to it (open circuit for dc).

Let the potential of point A be V_{C}.

Applying Kirchhoff’s second law from point A to ground via R_{B}, we have

Neglecting V_{BE} in comparison to collector potential V_{C} which is usually very small.

Now applying Kirchhoff’s second law for circuit starting from V_{CC} through collector to emitter terminal, we have

neglecting I_{B} being too small and I_{E} being almost equal to l_{C}.

Applying Kirchhoff’s second law to the circuit starting from collector point A to E via R_{B}

Comparing Eqs. (12.39) and (12.40) we have

Neglecting V_{BE}, being very small in comparison to supply voltage V_{CC},

The quiescent point, Q is thus established.

The circuit also stabilizes itself. Let the temperature of transistor junction rise when it is loaded. The increase in temperature causes increase in I_{C} and β. When l_{C} increases voltage drop in collector resistance R_{C} i.e. l_{C} R_{C} increases and potential of collector drops. This causes reduction in value of base current I_{B} which in turn reduces I_{C} being equal to βI_{B}.

**Stability factor S: **

Applying KVL to the input side, we have

Differentiating above equation w.r.t. l_{C} we have

Substituting this value in general expression for S, we have