One way to bias a BJT transistor is a method called base bias.

Base bias the simplest way to bias a BJT transistor. Base bias ensures that the voltage fed to the base, VBB, is the correct voltage, which then supplies the correct current so that the BJT has enough base current to switch the transistor on.

Base Bias Voltage/Current Calculations

When using any biasing technique, calculations must be made of the various voltages and currents through a BJT transistor. Or else, it's impossible to tell whether the voltage and current values are correct or not.

The first calculation we will make is for the base current IB.

The base current can be found by dividing the voltage across resistor RB by the value of RB. This is shown below:

IB= (VBB - VBE)/RB

Since the voltage drop across a silicon junction is 0.7V, the value of VBE=0.7V. Therefore, IB equals:

IB= (VBB - VBE)/RB= (5v - 0.7v)/56kΩ= 76.78µA

The collector current IC can be calculated next:

IC=βdc x IB= 100 x 76.78µA≈ 7.68mA

With IC then known, the collector-emitter voltage, VCE can be calculated. This is shown below:

VCE= VCC - IC x RC= 15v - (7.68mA x 1KΩ)= 7.32v 

Base bias can also be done with a single supply voltage, VCC, with VBB omitted. So instead of using VBB in calculations, you would just use VCC instead. The result of the calculatiosn are still the same, though.