Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
2N3442 NTE Electronics, Inc.	TRANS NPN 140V 10A TO204	0
2SA1955FVBTPL3Z Toshiba Electronic Devices and Storage Corporation	TRANS PNP 12V 0.4A VESM	10780
ZXTN4004KQTC Zetex Semiconductors (Diodes Inc.)	TRANS NPN 150V 1A TO252	0
BC808-25LT1G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 25V 500MA SOT23-3	2147483647
KSB1097YTU	TRANS PNP 60V 7A TO220F	940
BC807-40-7-F Zetex Semiconductors (Diodes Inc.)	TRANS PNP 45V 0.5A SOT23-3	3584
FMMT549 Sanyo Semiconductor/ON Semiconductor	TRANS PNP 30V 1A SUPERSOT-3	11056
BC327-25-AP Micro Commercial Components (MCC)	TRANS PNP 45V 0.8A TO-92	0
BC337-25 B1G TSC (Taiwan Semiconductor)	TRANSISTOR, NPN, 45V, 0.8A, 160A	0
DXT2014P5-13 Zetex Semiconductors (Diodes Inc.)	TRANS PNP 140V 4A POWERDI5	6248
BC847AQBZ Nexperia	BIPOLAR DISCRETES	4484
2N5655G	TRANS NPN 250V 500MA TO225AA	23874
KST3906MTF	SMALL SIGNAL BIPOLAR TRANSISTOR	26161
FMMT555TC Zetex Semiconductors (Diodes Inc.)	TRANS PNP 150V 1A SOT23-3	10597
NSS40300MZ4T1G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 40V 3A SOT-223	1885
FZT688BTA Zetex Semiconductors (Diodes Inc.)	TRANS NPN 12V 4A SOT223	641515000
MMBTA42LT1G	SMALL SIGNAL BIPOLAR TRANSISTOR,	755750
2SB1184TLP ROHM Semiconductor	TRANS PNP 50V 3A SOT-428	0
HFA3127MJ/883	DUAL MARKED (5962-9474901MEA)	1027
MBT35200MT1	TRANS PNP 35V 2A 6TSOP	33000

Transistors - Bipolar (BJT) - Single

1. Overview

Bipolar Junction Transistors (BJTs) are three-terminal semiconductor devices that use both electron and hole charge carriers. They form the foundation of analog electronics through their ability to amplify signals and control current flow. BJTs remain critical in modern electronics for applications ranging from audio amplifiers to power management circuits, offering superior linearity and robustness in switching operations.

2. Main Types & Functional Classification

Type	Functional Characteristics	Application Examples
NPN Transistor	Majority carriers: electrons. Requires positive base current for conduction.	Low-noise amplifiers, digital logic circuits
PNP Transistor	Majority carriers: holes. Conducts with negative base current.	Power supply circuits, motor controllers
High-Frequency BJT	Optimized for RF/microwave signal amplification (f_T > 100 MHz)	Wireless communication systems, radar
Power BJT	High current/voltage ratings (I_C > 1A, V_CE > 50V)	Switch-mode power supplies, motor drives

3. Structure & Composition

BJTs consist of three doped semiconductor regions forming two p-n junctions:

Emitter: Heavily doped region emitting charge carriers
Base: Thin, lightly doped middle region controlling carrier flow
Collector: Moderately doped region collecting carriers

Manufactured using silicon (common) or germanium (historic) with planar processing technology. The structure forms either NPN (n-type emitter/base/collector) or PNP configuration, with metal contacts for external connections.

4. Key Technical Specifications

Parameter	Description	Importance
Current Gain (h_FE)	Ratio of collector to base current (10-1000)	Determines amplification capability
Transition Frequency (f_T)	Frequency at which current gain drops to 1	Limits high-frequency performance
Max Collector Current (I_Cmax)	Maximum allowable continuous collector current	Defines power handling capability
Breakdown Voltage (V_CEO)	Max voltage between collector and emitter	Prevents device failure under stress
Saturation Voltage (V_CEsat)	Voltage drop in fully conducting state	Affects power efficiency in switching

5. Application Areas

Consumer Electronics: Audio amplifiers, LED drivers
Automotive: Engine control units, electric vehicle inverters
Industrial: PLCs, motor controllers
Telecommunications: RF power amplifiers, fiber optic transceivers
Aerospace: Avionics systems, satellite transponders

6. Leading Manufacturers & Products

Manufacturer	Product Series	Key Specifications	Typical Use
ON Semiconductor	2N3904	hFE: 100-300, fT: 300 MHz	General-purpose switching
Infineon	BC547	VCEO: 50V, ICmax: 100mA	Analog signal amplification
STMicroelectronics	2SD2656	ICmax: 15A, VCEO: 80V	Power inverter applications
Diodes Inc.	BFR93A	fT: 10 GHz, Noise Figure: 2dB	High-frequency front-end amplifiers

7. Selection Guidelines

Determine operating frequency: Select fT > 3 target frequency
Power requirements: Ensure Icmax and VCEO exceed circuit requirements by 20%
Thermal considerations: Calculate power dissipation (P=V_CE I_C)
Package type: TO-92 for low power, TO-220 for high-power applications
Environmental factors: Consider temperature ratings for industrial/military use

8. Industry Trends

Future developments include:

High-frequency BJTs operating beyond 100 GHz for 6G communication
Integrated BJT-MOSFET hybrid devices (BiCMOS) for mixed-signal applications
Wide-bandgap materials (SiC/GaN) for higher power density
Miniaturization through chip-scale packaging
Improved thermal management solutions for automotive applications