Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Image	Part Number	Description / PDF	Quantity	Rfq
	2N3904T93 ROHM Semiconductor	TRANS NPN 40V 0.2A TO-92	0
	2SD1963T100S ROHM Semiconductor	TRANS NPN 20V 3A SOT-89	0
	2SC4505T100P ROHM Semiconductor	TRANS NPN 400V 0.1A SOT-89	0
	2SD1468STPR ROHM Semiconductor	TRANS NPN 15V 1A 3PIN SPT	0
	QSX3TR ROHM Semiconductor	TRANS NPN 30V 5A TSMT6	0
	2SB1326TV2R ROHM Semiconductor	TRANS PNP 20V 5A ATV	0
	BSS63T116 ROHM Semiconductor	BSS63 IS A SOT-23 PACKAGE TRANSI	0
	BCX71JT116 ROHM Semiconductor	TRANS PNP 45V 0.2A SST3	0
	2SC4015TV2N ROHM Semiconductor	TRANS NPN 300V 0.1A ATV	0
	2SB1308T100P ROHM Semiconductor	TRANS PNP 20V 3A SOT-89	0
	2SC2389STPS ROHM Semiconductor	TRANS NPN 120V 0.05A 3PIN SPT	0
	2SD2170T100 ROHM Semiconductor	TRANS NPN DARL 90V 2A SOT-89	0
	2N3906T93 ROHM Semiconductor	TRANS PNP 40V 0.2A TO-92	0
	2SC1740STPR ROHM Semiconductor	TRANS NPN 50V 0.15A SC-72	0
	BSS4130T116 ROHM Semiconductor	BSS4130 IS A SOT-23 PACKAGE TRAN	0
	2SD2167T100P ROHM Semiconductor	TRANS NPN 31V 2A SOT-89	0
	2SA1585STPR ROHM Semiconductor	TRANS PNP 20V 2A SPT	0
	BSS64T116 ROHM Semiconductor	BSS64 IS A SOT-23 PACKAGE TRANSI	0
	2SD1862TV2Q ROHM Semiconductor	TRANS NPN 32V 2A ATV	0
	2SA933ASTPQ ROHM Semiconductor	TRANS PNP 50V 0.15A SPT	0

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