Edexcel GCSE Design and Technology · 1DT0
Specification 5.2.2 · Paper 1
Revise: Control Devices and ComponentsA bipolar transistor has three terminals: base, collector and emitter. In a typical NPN switching circuit, a small current entering the base allows a larger current to flow through the load and from collector to emitter. With no base current, the transistor switches off that collector current.