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.

Equations

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-V_BE)/Ib= (VP-V_BE)*Beta/Ic= (VP-V_BE)*Beta*Rc/VP