Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
RXT2907AT100 ROHM Semiconductor	TRANS NPN MPT3	0
2SA1774EBTLQ ROHM Semiconductor	TRANS PNP 50V 0.15A EMT3F	0
BC847BU3HZGT106 ROHM Semiconductor	NPN GENERAL PURPOSE TRANSISTOR (	2847
2SC5868TLQ ROHM Semiconductor	TRANS NPN 60V 0.5A TSMT3	4328
2SCR572D3TL1 ROHM Semiconductor	POWER TRANSISTOR WITH LOW VCE(SA	1037
MMST6428T146 ROHM Semiconductor	TRANS NPN 50V 0.2A SMT3	0
BCW32T116 ROHM Semiconductor	TRANS NPN 32V 0.1A SST3	0
BC848CT116 ROHM Semiconductor	TRANS NPN 30V 0.1A SST3	0
2SC4725TLP ROHM Semiconductor	TRANS NPN 20V 0.05A SOT-416	2000
2SA1576U3HZGT106R ROHM Semiconductor	GENERAL PURPOSE TRANSISTOR (-50V	179
2SCR574D3TL1 ROHM Semiconductor	POWER TRANSISTOR WITH LOW VCE(SA	2595
2SD2662T100 ROHM Semiconductor	TRANS NPN 30V 1.5A SOT-89	875
2SCR533PT100 ROHM Semiconductor	TRANS NPN 50V 3A SOT-89	949
2SA2018TL ROHM Semiconductor	TRANS PNP 12V 0.5A SOT-416	1286
2SC4097T106R ROHM Semiconductor	TRANS NPN 32V 0.5A SOT-323	6858
2SAR542F3TR ROHM Semiconductor	TRANS PNP 30V 3A HUML2020L3	1222
2SB1260T100Q ROHM Semiconductor	TRANS PNP 80V 1A SO-89	1182
SST2907AT116 ROHM Semiconductor	TRANS PNP 60V 0.6A SSD3	21329
2SD2653TL ROHM Semiconductor	TRANS NPN 12V 2A TSMT 3	0
2SD2153T100V ROHM Semiconductor	TRANS NPN 25V 2A SOT-89	999

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