A unijunction transistor is a solid-state device that operates as an electrically controlled switch rather than an amplifier. It consists of a single piece of N-type semiconductor material with two base contacts and a single P-type emitter junction. When the emitter voltage reaches a specific threshold, the device exhibits negative resistance, causing a sharp drop in voltage. This snap-action makes it ideal for building simple relaxation oscillators and generating precise trigger pulses for power control components.
Check the unijunction on the timing board to see if it's still firing the trigger pulse to the SCR.
The defining characteristic of a unijunction transistor is its intrinsic standoff ratio, which dictates the exact voltage at which the device snaps on.
Also heard as
- UJT
- unijunction transistor