2N1799

Thyristors - SCRs

A silicon controlled rectifier (SCR) or a thyristor is typically a four-layer semiconductor device. It has three terminals (anode, cathode, and gate, typically abbreviated A, K and G, respectively) and can be used both as a switch or as an amplifier, depending on its configuration. An SCR can be triggered ‑ turned on ‑ by heat or electricity.

The 2N1799SCR is intended primarily for full-wave and half-wave rectification in power-supply circuits. It is used in applications such as AC dimmers, AC lighting and motor control, DC-to-DC converters, and static and dynamic power supplies.

Application Field

The 2N1799 application field covers commercial, industrial, aviation, and military requirements. It has many uses in the communication industry such as triggering switching relays, regulating inverter and transistor output voltages, and providing phase control functions.

It can also be used as a local power supply regulator and in frequency-controlled lighting dimmers. It is suitable for use in ac motor drives, frequency control circuits, and servo systems. In the medical field, it can be used in medical instruments such as infusion pumps, patient monitors, and glucometers.

In the automotive industry, the 2N1799 can be used as an electronic switch in brake systems, fuel injection systems, and electronic engine control systems. It can also be used in audio and lighting system controllers, sensors, and many other applications.

Working Principle

The SCR consists of four layers of doped silicon sandwiched together and attached to three electrodes. An idea of how it works is given by the figure below. The P-type region is called the anode, the N-type region is called the cathode and the gate controls the current flow. The 2N1799 is a type of two-terminal device.

When a positive voltage is applied to the anode and a negative voltage is applied to the cathode, current flows through the device. This is called “forward” conduction. If the polarity of the voltage applied is reversed, no current flows.

In order to turn the SCR “on” and make it start conducting, a small pulse of current must be applied to the gate. This causes the junction between the P and N regions to become forward biased and current begins to flow. This process is called “triggering”.

Once the SCR has been turned on, current will continue to flow between the anode and cathode, even if the voltage applied is removed from the gate. The current through the SCR is then determined by the voltage between the anode and cathode, and is known as the “holding current”. In order to turn the SCR off, the voltage must be reversed.

Conclusion

The 2N1799 SCR is a versatile component that can be used in a wide range of applications. The SCR\'s ability to be triggered on and off makes it suitable for switching and amplifying various types of signals. Its four layers of silicon and three terminals can be used to create a switch or amplifier that is controlled by heat or electricity.