Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
2SAR572D3TL1 ROHM Semiconductor	POWER TRANSISTOR WITH LOW VCE(SA	2477
MMST4401T146 ROHM Semiconductor	TRANS NPN 40V 0.6A SOT-346	11
2SAR523EBTL ROHM Semiconductor	TRANS PNP 50V 0.1A EMT3F	1560
2SD2096T114E ROHM Semiconductor	TRANS NPN 60V 3A HRT/TO-220FP	613
RXT2222AT100 ROHM Semiconductor	TRANS NPN MPT3	0
2SC4617EBTLS ROHM Semiconductor	TRANS NPN 50V 0.15A EMT3	0
BCW72T116 ROHM Semiconductor	TRANS NPN 45V 0.1A SST3	0
2SA1579T106S ROHM Semiconductor	TRANS PNP 120V 0.05A SOT-323	0
2SAR512PT100 ROHM Semiconductor	TRANS PNP 30V 2A MPT3	2032
2SC4102T106S ROHM Semiconductor	TRANS NPN 120V 0.05A SOT-323	0
2SCR553RTL ROHM Semiconductor	NPN DRIVER TRANSISTOR	2723
2SCR544PFRAT100 ROHM Semiconductor	NPN DRIVER TRANSISTOR (CORRESPON	1000
2SB1188T100R ROHM Semiconductor	TRANS PNP 32V 2A SO-89	1000
2SA1774TLS ROHM Semiconductor	TRANS PNP 50V 0.15A SOT-416 TR	47
2SA2007E ROHM Semiconductor	TRANS PNP 60V 12A TO220FN	500
2SCR372P5T100Q ROHM Semiconductor	NPN 120V 700MA MEDIUM POWER DRIV	1252
2SB1132T100Q ROHM Semiconductor	TRANS PNP 32V 1A SO-89	0
2SAR340QTR ROHM Semiconductor	PNP -100MA -400V MIDDLE POWER TR	2930
2SC2412KT146R ROHM Semiconductor	TRANS NPN 50V 0.15A SOT-346	89
2SAR502U3HZGT106 ROHM Semiconductor	PNP 500MA 30V GENERAL PURPOSE TR	2574

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