BT137-800.127 is a TRIAC thyristor manufactured by NXP Semiconductors. It is suitable for blocking and controlling the current in AC power applications and switching circuits. It has a VDRM of 800V, a VRRM of 800V, a IGT of 15mA, an IT (RMS) of 8A, a IH (AV) of 3A, a di/dt of 4.68A/µs, and a dv/dt of 900V/µs. It comes in a TO-220AA package and is typically used for driving small AC loads such as lamps in power conversion applications.