Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
2SCR586D3FRATL ROHM Semiconductor	2SCR586D3FRA IS A POWER TRANSIST	2322
2SD2702TL ROHM Semiconductor	TRANS NPN 12V 1.5A TUMT3	1256
2SD2226KT146V ROHM Semiconductor	TRANS NPN 50V 0.15A SOT-346	0
2SCR523MT2L ROHM Semiconductor	TRANS NPN 50V 0.1A VMT3	7894
2SC5865TLQ ROHM Semiconductor	TRANS NPN 60V 1A TSMD3	0
BC848BT116 ROHM Semiconductor	TRANS NPN 30V 0.1A SST3	0
2SB1731TL ROHM Semiconductor	TRANS PNP 30V 1.5A TUMT3	25
2SD2098T100S ROHM Semiconductor	TRANS NPN 20V 5A SOT-89	0
2SCR554RTL ROHM Semiconductor	TRANS NPN 80V 1.5A TSMT3	195
2SB1184TLR ROHM Semiconductor	TRANS PNP 50V 3A SOT-428	0
2SCR375P5T100R ROHM Semiconductor	NPN 120V 1.5A MEDIUM POWER TRANS	1683
2SC4505T100Q ROHM Semiconductor	TRANS NPN 400V 0.1A SOT-89	0
2SC4617EBTLQ ROHM Semiconductor	TRANS NPN 50V 0.15A EMT3	103
2SD2671TL ROHM Semiconductor	TRANS NPN 30V 2A TSMT3	2995
2SD2696T2L ROHM Semiconductor	TRANS NPN 30V 0.4A VMT3	5192
2SC4081U3T106R ROHM Semiconductor	GENERAL PURPOSE SMALL SIGNAL AMP	0
2SC4081U3HZGT106Q ROHM Semiconductor	2SC4081U3HZG IS A TRANSISTOR WIT	0
2SC5876U3T106 ROHM Semiconductor	2SC5876U3 IS THE HIGH SPEED SWIT	3239
2SC4102U3HZGT106R ROHM Semiconductor	HIGH-VOLTAGE AMPLIFIER TRANSISTO	2317
2SA2094TLQ ROHM Semiconductor	TRANS PNP 60V 2A TSMT3	6638

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