Automatic Biasing Resistance (MA109E)

To increase the performance of a common emitter amplifier using a transistor the base-biasing resistor can be wired as shown in figure. The following formula is used to calculated this resistor.

 

Formula 1

Base resistor:

RB = Vce / IB

Where:

RB is the base resistance in ohm (Ω)

V_CE is the voltage between collector and emitter in volts (V)

I_B is the base current in amperes (A)

Application example:

Determine the base-biasing resistor in a circuit where the collector voltage is 6 V and base current is 50 µA.

Data:

Vce = 6 V

IB = 50 µA

Applying formula 1

RB = 6 / (50 x 10^-6)

RB = (6 / 50) x 10⁶

RB = 0.12 x 10⁶

RB = 120 kΩ