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