A Unijunction transistor (UJT) is an electronic semiconductor device.
There are two types of unijunction transistors:
- The original unijunction transistor, or UJT, is a simple device that is essentially a bar of N type semiconductor material into which P type material has been diffused somewhere along its length. The 2N2646 is an example of such a device.
- The programmable unijunction transistor, or PUT, is a close cousin to the thyristor. Like the thyristor it consist of four P-N layers and has an Anode and a Cathode connected to the first and the last layer, and a Gate connected to one of the inner layers. They are not directly interchangeable with conventional UJTs but perform a similar fuction. The 2N6027 is an example of such a device.
For both types, their main use is as unijunction transistor a trigger device for thyristors and as the active device in relaxation oscillators. The graph of emitter voltage against emitter current of a unijunction transistor shows an area of negative resistance; this is what makes the UJT useful.
Electronics Topics
The field of electronics is the study and use of systems that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. The design and construction of electronic circuits to solve practical problems is part of the fields of electronic engineering, and the hardware design side of computer engineering. The study of new semiconductor devices and their technology is sometimes considered as a branch of physics.
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