This configuration employs negative feedback to prevent thermal runaway and stabilize the operating point. In this form of biasing, the base resistor formula_1 is connected to the collector instead of connecting it to the DC source formula_2. So any thermal runaway will induce a voltage drop across the formula_3 resistor that will throttle the transistor's base current.

From Kirchhoff's voltage law, the voltage formula_4 across the base resistor formula_1 is

By the Ebers–Moll model, formula_7, and so

From Ohm's law, the base current formula_9, and so

Hence, the base current formula_11 is

If formula_13 is held constant and temperature increases, then the collector current formula_14 increases. However, a larger formula_14 causes the voltage drop across resistor formula_16 to increase, which in turn reduces the voltage formula_4 across the base resistor formula_1. A lower base-resistor voltage drop reduces the base current formula_11, which results in less collector current formula_14. Because an increase in collector current with temperature is opposed, the operating point is kept stable.

लाभ:

अलाभ:

which is the case when


उपयोग:
The negative feedback also increases the input impedance of the amplifier as seen from the base, which can be advantageous.
Due to the gain reduction from feedback, this biasing form is used only when the trade-off for stability is warranted.

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