BJT Transistor as a Switch, Saturation Calculator
A BJT transistor can be used as an electronic switch when it is driven into saturation, or alternatively driven to the cut off region. Calculating the base resistor is a common engineering task, which this calculator automates.
The current through the load at saturations is Ic= VP/Rc. The base current must be Ib= Ic/Beta. Transistors have a varying gain so we want to use the minimum beta value, to ensure saturation.
Rb= (VP-VBE)/Ib= (VP-VBE)*Beta/Ic= (VP-VBE)*Beta*Rc/VP