Trigger Devices Trigger devices come under a variety of different classifications, with somewhat differing characteristics Unijunction Transistors Unidirectional Switches a Bidirectional Switches ( Bilateral Triggers 4-Layer Diodes PUT DIAC SBS SUS UJT the principal function of all these is to act as trigger devices for SCR and Triac circuits. Motorola makes them all, and with sufficient breadth of specifications to meet any circuit requirement. The variety of different trigger devices available complicates device selection. No specific type of trigger has a clear-cut advantage over all others. Hence, trigger selection is often very subjective, based on the designers experience and familiarity. Nevertheless, some basic comparisons can be drawn that might simplify the job of trigger selection for designers who have not already formed specific preferences. Programmalle Unijunction Transistors PUT Similar to UJTs, except that ly, Ip and intrinsic standoff voltage are programmable (adjustable) by means of external voltage divider. This stabilizes circuit performance for variations in device parameters. General operating frequency range is from 0.01 Hz to 10 kHz, making them suitable for long-duration timer circuits. Two-package availability provides cost option. Ip ly ) sce T Rg= Ro= IGAO Rg= Rg= Package Device Type 10 kQ 1.0 MQ @40V 10k 1.0MQ LA Max nA Max. UA Min. LA Max. Plastic 2N6027 5.0 2.0 10 70 50 Case 29-02 2N6028 1.0 0.15 25 25 (TO-92) MPU131 5.0 2.0 5.0 70 50 MPU132 2.0 0.3 5.0 50 50 MPU133 1.0 0.15 5.0 50 25 Bilateral Triggers - DIACs Specifically designed as low-cost bidirectional triggers in line-operated Triac control circuits such as light dimmers, motor controls and temperature controls. ( Vs Volts Is Package Device Type Nom UA Max. mA Max. \ Min. Max. yy, Plastic 1N5758/MPT20 20 + 40 100 ) Case 182-02 1N5759 24 + 4.0 100 (TO-92) 1N5760/MPT28 28 + 4.20 100 4N5761/MPT32 32 + 40 100 1N5762 36 + 4.0 100 1N57584 20 + 2.0 25 1N57594 24 + 20 25 1N5760A 28 + 2.0 25 1IN5761A 32 + 2.0 25 1N5762A 36 + 2.0 25 y Silicon Bidirectional Switch SBS Applications similar to Diac, but has gate electrode that permits synchronization. Plastic MBs4g91 6.0 10 500 15 Case 29-02 MBS4992 7.5 9.0 120 0.5 (TO-92) 10-7