Pro Electron - Semiconductor Diodes and Transistors

Semiconductor Diodes and Transistors

As listed above, he first letter gives the semiconductor type; the second letter denotes the intended use:

2nd letter	Usage	Example
A	Low power/small signal diode	AA119, BA121
B	Varicap diode	BB105G
C	Small signal transistor, RthG > 15K/W	BC546C
D	High power, low frequency power transistor, RthG ≤ 15K/W	BD139
E	Tunnel (Esaki-)diode	AE100
F	Low power, RF (high frequency) Bipolar or FET, RthG > 15K/W	BF245
G	Hybrid device	BGY32, BGY585
H	Hall effect sensor/diode
L	High frequency, high power transistor (for transmitters), RthG ≤ 15K/W	BLW34
M	Ring modulator-type frequency mixer
N	Opto-isolator	CNY17
Q	Radiation generator (LED)	CQY99
R	Low-power control or switching device: Thyristors, Diacs, Triacs, UJTs, Programmable uni-junction transistors (PUT), Silicon bidirectional switch (SBS), Opto-triacs etc.	BR100
S	Low-power switching transistor, bipolar or MOSFET, RthG > 15K/W	BS170
T	High-power control or switching device: Thyristors, TRIACs, Silicon bidirectional switch (SBS), etc.	BT138
U	High-power switching transistors, bipolar or MOSFET, RthG ≤ 15K/W	BU508, BUZ11
V	Antenna
W	Surface acoustic wave device
X	Frequency multiplier: Varactor, Step recovery diode
Y	High-power rectifying diode	BY228
Z	Avalanche, TVS, Zener diode	BZY91

A 3-digit sequence number (or one letter then 2 digits, for industrial types) follows. Examples are:

Prefix class	Usage	Example
AC	Germanium small signal transistor	AC126
AF	Germanium RF transistor	AF117
BC	Silicon, small signal transistor ("allround")	BC548B
BD	Silicon, power transistor	BD139
BF	Silicon, RF (high frequency) BJT or FET	BF245
BS	Silicon, switching transistor Bipolar or MOSFET)	BS170
BL	Silicon, high frequency, high power (for transmitters)	BLW34
BU	Silicon, high voltage (for CRT horizontal deflection circuits)	BU508

With early devices, the number indicated the case type. Suffixes may be used, such as a letter (e.g. "C" often means high h_FE, such as in: BC549C). Other codes may follow to show gain (e.g. BC327-25) or voltage rating (e.g. BUK854-800A). A BC546 might only be marked "C546", thus possibly creating confusion with JIS abbreviated markings, because a transistor marked "C546" might also be a 2SC546.

• Short summary of semiconductor diode and transistor designations

BC549C / \ \ \___ variant (A,B,C for transistors implies low, medium or high gain) / \ \____ serial number (3 digits or letter and 2 digits) / \_____ device type: A=Germanium A=Signal Diode B=Silicon C=LF Low Power transistor C=GaAs D=Power transistor F=RF transistor (or FET) P=Photosensitive transistor T=Triac or Thyristor Y=Rectifier Diode Z=Zener diode