WEE Technology Company Limited

Manufacturer of Surface Mount (SMD) and Through Hole (DIP) Diodes & Rectifiers

BC817 NPN general-purpose transistor in a small SOT23 (TO-236) Surface-Mounted Device (SMD) plastic package, but with high collect current and high DC current gain. SMD General Purpose Transistor (NPN) 45 V, 500 mA usually used for switching and AF Amplifier Applications 

BC817-40LT1G also known as Bipolar Transistors - BJT, BC817-16 marking as 6A, BC817-25 marking as 6B, BC817-40 marking as 6C.

So how to recognize the marking code for SMD General Purpose Transistors? WEET engineers would like to share more with you.

The European used to name transistors begins with A or B (A denotes germanium tube and B denotes silicon tube). 

The second part uses C, D or F, L (C-low frequency small power tube, F-high frequency small power tube, D-low frequency high power tube, L-high frequency high power tube); 

S and U usually stands for small power switching and high power switching transistors respectively; 

The third part uses three digits to denote each serial number or part number.

For example, BC817 represents a silicon low-frequency low-power transistor (fT = 200MHz) and a universal small-signal amplifier transistor. 

There are also some transistors models named by the manufacturer itself (factory standard), which are not standard in the market. 

https://www.weetcl.com/pdf/WEET_Transistors_SOT-23_BC817_BC818.pdf