What is Forced Beta?

[Justin_Wiseth]

Forced Beta is a term used to describe when the BJT is operated as a switch in saturation. When this occurs, the base current is equal to 10% of the collectors current. This is especially handy when calculating what current limiting resistor to use.

[Klint_12443]

What happens if the base’s current is more than 10% of the collectors? (aka what happens if I choose the wrong resistor on the base?)

[APDahlen]

See also:

Digital Switching: Transistor Saturation and Forced Beta

Transistors are often used as controlled switches in digital circuits. For example, a transistor may be used as a buffer allowing a microcontroller to activate a relay or LED. For these digital applications, we want the transistor to be saturated so that the collector to emitter appears as a short circuit; like a closed switch, current is free to flow from emitter to collector. In this post we will explore saturation and complications arising from nonlinear response of the transistor’s beta, es…