What is a unijunction transistor and is it a transistor?
The unijunction transistor is more a thyristor than a transistor. It has one junction and was once referred to as a double-base diode. The UJT, unijunction transistor, doesn t conduct until a peak voltage, Vp, is reached. At that time the emitter conducts, resulting in a positive pulse at B1 and a negative pulse at B2 either of which can be used to trigger another device such as an SCR. The UJT is often used with an RC timer circuit (see below), and can operate up to 1 Mhz.
