Skip to datasheet
NPN Darlington power transistor

TIP122 Working Principle

Learn how TIP122 works with an illustrated explanation and practical readings.

TIP122 at a glance

Follow the labeled connections and functional stages

TIP122 working principle: illustrated functional stages, basic circuit and connections
Select the diagram to read it at full resolution.

How it works

3 stages · Explore one step at a time

Step 1 / 3

Drive the first base

The external base current enters the first NPN stage.

Step 2 / 3

Multiply current drive

Its emitter drives the second stage while both collectors remain common.

Step 3 / 3

Check voltage and heat

A Darlington needs voltage headroom and appropriate cooling.

Component view