Description-
BT136-600D Transistor is a TRIAC with 4A maximum terminal current and low threshold voltage of the so it can be driven by digital circuits. Since TRIACs are bi-directional switching devices, they are commonly used for switching AC applications. So if you want to switch control (dim, speed control) an AC load (less than 6A) with a digital devices like microcontroller or microprocessor then BT136 might be the right be the right choice.
 
Specifications-
-Maximum terminal current : 4A
-On-state gate voltage : 1.4V
-Gate trigger current : 10mA
-Max terminal voltage : 600 V
-Holding current : 2.2mA
-Latching current : 4mA
 
Applications / Suggested Uses -
AC Light dimmers
Strode lights
AC motor speed control
Noise coupling circuits
Controlling AC loads using MCU/MPU
Ac/DC Power control
Tips-
Since TRIACS deal with AC voltages, the circuit involving them has to be designed properly to avoid problems some tips are shared below-
1.All TRIAC circuits suffer from an effect called Rate Effect. This occurs when the TRIAC is switching frequently and a sudden high voltage occurs at either main terminal of the TRIAC and damages the TRIAC itself. It can be avoided by using a snubber circuit.
2. Similarly, there is another effect called the backlash effect. This occurs due to the capacitance that gets accumulated between the two terminals of the MT1 and MT2 of the TRIAC. Due to this, the TRIAC will not turn on even if the gate voltage is applied. This problem can be solved by providing resistance in series for the capacitance to discharge.
3. When controlling the output AC voltage for dimmer or speed control applications a Zero crossing method is always recommended to be used.
4. In switching circuits the TRIAC is easily subjected to harmonics and EMI interference hence should be isolated from other digital electronics.
5.There is a chance of backward current when the TRIAC is switching inductive loads, so an alternate discharge path has to be provided for the load to drain the inrush current.