Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
2SB1695KT146 ROHM Semiconductor	TRANS PNP 30V 1.5A SMT3	2969
2SCR341QTR ROHM Semiconductor	NPN 100MA 400V MIDDLE POWER TRAN	2925
2SD1782KT146R ROHM Semiconductor	TRANS NPN 80V 0.5A SOT-346	0
2SB1698T100 ROHM Semiconductor	TRANS PNP 30V 1.5A SOT-89	1371
MMST5088T146 ROHM Semiconductor	TRANS PNP SMT3	0
2SD2704KT146 ROHM Semiconductor	TRANS NPN 20V 0.3A SOT23-3	55098
2SA1514KT146S ROHM Semiconductor	TRANS PNP 120V 0.05A SOT-346	2920
2SCR522EBTL ROHM Semiconductor	TRANS NPN 20V 0.2A EMT3F	503
2SD2391T100Q ROHM Semiconductor	TRANS NPN 60V 2A SOT-89	1000
2SCR542PFRAT100 ROHM Semiconductor	NPN DRIVER TRANSISTOR (CORRESPON	202
BSS4130AHZGT116 ROHM Semiconductor	BSS4130AHZG IS A SOT-23 PACKAGE	2965
2SC5659T2LP ROHM Semiconductor	TRANS NPN 25V 0.05A VMT3	7740
2SD2672TL ROHM Semiconductor	TRANS NPN 12V 4A TSMT3	0
2SD2150T100S ROHM Semiconductor	TRANS NPN 20V 3A SOT-89	0
2SC5053T100Q ROHM Semiconductor	TRANS NPN 50V 1A SOT-89	485
2SD2654TLW ROHM Semiconductor	TRANS NPN 50V 0.15A EMT3	230
QST2TR ROHM Semiconductor	TRANS PNP 12V 6A TSMT6	3000
BSS63AT116 ROHM Semiconductor	TRANS 100V 100A SOT-23	2367
2SC5729T106R ROHM Semiconductor	TRANS NPN 30V 0.5A SC70	0
2SAR586D3TL1 ROHM Semiconductor	POWER TRANSISTOR WITH LOW VCE(SA	633

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