The SJ4020R2ATP from Littelfuse is a Silicon Controlled Rectifier with Breakover Voltage 400 V, Breakover Current 20 A, Gate Trigger Voltage 1.6 V, Gate Trigger Current 0.01 A, Temperature Operating Range -40 to 150 Degree C. Tags: Through Hole. More details for SJ4020R2ATP can be seen below.