The Four Layers of Thyristor Terminals

A thyristor is an electrical semiconductor device having four layers of N and P-type material. It behaves solely as a bistable switch; conducting only when the external voltage causes the gate to become non-bistable and proceeding to conduct when the external voltage is pulled away from the device. This simple device can be used in digital circuits where one or more input terminals require an electrical current to pass through them. There are two types of thyristors available, conductors or resistors, or coupled devices.

The most common use for a thyristor in digital circuits is as a linear regulator. A linear regulator is designed so that it only responds to the changes in the value of its input resistance. This is done by adjusting the control curve to a value where the output is dictated by the input current level.

A thyristor consists of a series of thin conductors bonded to a substrate, which is also in layered arrangement. The thin layer of layers make the thickness of the device less than the thickness of a single diode, thus enabling the current to pass through them without being negatively affected. The layers are generally made of P-type, N-type, or mixed materials, but the final choice of material depends on the application needs of the end application or the circuitry that the thyristor will be installed in.

While some companies use thyristors as a generic term for any type of semiconductor device, others prefer to label them with specific applications. Some examples include PMT (Pulse-regulated Transistor Technology), PMMA (Metal Oxide Semiconductor), and JEDEC (Just Inside Outside Circuit). Each of these specific acronyms corresponds to a specific p-type, N-type, or mixed material thyristor that is available for use in a specific application. Because of their flexibility and cost effectiveness in the market, many companies that utilize these in their designs and manufacturing processes prefer to purchase them in bulk so that they have a ready supply when required.


One example of a thyristor application is in the case of PMT. A thyristor is used to protect against the occurrence of excessive heat build-up within an anode. To accomplish this, the anode’s gate is attached to the base of the transistor using a positively-charged intermediary, which is called the gate electrode. Because heat builds up at the anode during startup and operation, the PMT protects against damage to the anode. Since most PMT is soldered to the aluminum base during production, it is important that the company purchasing them uses high quality products, which are subject to stringent testing standards.


There are several types of these products, each designed to deliver different results depending on the function involved. For example, a pilot light requires protection against the discharge of vapors during start-up. A gate drive requires protection against the build-up of solvents at the tip; and anodes require protection against excessive heat build-up. Thyristor devices with these four layers are therefore commonly called PMT (passive mpt) or GP TM (high-performance trimming valve) and are ideal for applications where speed, temperature and/or power are a concern.

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