Thyristors - TRIACs

A TRIAC (Triode for Alternating Current) is an electronic device that acts as a bidirectional switch for AC signals. It is the most commonly used type of thyristor. TRIACs are widely used for various applications, such as light dimmers, speed controls for electric motors, and household appliances such as washing machines, air conditioners, and dishwashers. The BT139B-600 at 118 is a type of TRIAC.

Working Principle

In order to understand how a TRIAC works, one must first understand how an SCR (Silicon Controlled Rectifier) works. A TRIAC is essentially two SCRs connected together in an inverse parallel configuration. Unlike SCRs, both the anode and cathode terminals of a TRIAC are "active", which means that current can flow through the device in either direction when it is in the on-state. TRIACs require a current control signal in order to transition from the off to on state—this is typically a small voltage pulse applied to the control terminal of the device. When the control signal reaches the threshold voltage, a short current pulse is created in either direction of the main terminals, which turns the TRIAC on.

Application Field

The BT139B-600 at 118 is a popular TRIAC for a variety of applications such as AC motor speed control, light dimming, heater regulation, and more. It is a sensitive gate device, making it suitable for use in many different applications where precise voltage control is required. The device is also very low cost, which makes it ideal for home automation and DIY projects. In addition, the BT139B-600 has a higher maximum current rating than many other similar TRIACs. This makes it suitable for applications that draw more than 1A, including lighting and electric motor control.

The BT139B is available in both TO-220 and TO-92 packages and has a maximum on-state voltage of 56V. It has a maximum current rating of 10A and is rated for temperatures up to 125 degrees Celsius. It is also available in a range of gate sensitivities (VGT) from 1.5V to 6V. This makes it suitable for applications where precise control of the on/off state is required.

Overall, the BT139B-600 at 118 is a versatile TRIAC with a wide range of applications. It is a cost-effective solution for many AC applications, and its low on-state voltage ensures high reliability and low power loss. It is also the ideal device for home automation projects, as it offers precise control of loads and flexible installation.