Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Image	Part Number	Description / PDF	Quantity	Rfq
	2SB1237TV2P ROHM Semiconductor	TRANS PNP 32V 1A ATV	0
	2SC3415STPN ROHM Semiconductor	TRANS NPN 300V 0.1A 3PIN SPT	0
	2SC5731T100Q ROHM Semiconductor	TRANS NPN 30V 2A SOT-89	0
	2SD1859TV2R ROHM Semiconductor	TRANS NPN 80V 0.7A ATV	0
	2SD2097TV2R ROHM Semiconductor	TRANS NPN 20V 5A ATV	0
	US6X3TR ROHM Semiconductor	TRANS NPN 12V 3A TUMT6	0
	2SC5732TLQ ROHM Semiconductor	TRANS NPN 30V 5A SOT-428	0
	2SD2144STPV ROHM Semiconductor	TRANS NPN 20V 0.5A SPT/SC-72	0
	2SA1585STPQ ROHM Semiconductor	TRANS PNP 20V 2A SPT	0
	2SB1565FU6E ROHM Semiconductor	TRANS PNP 60V 3A TO220FN	0
	BCW33T116 ROHM Semiconductor	TRANS NPN 32V 0.1A SST3	0
	2SB1236TV2Q ROHM Semiconductor	TRANS PNP 120V 1.5A ATV	0
	2SB1243TV2R ROHM Semiconductor	TRANS PNP 50V 3A ATV	0
	2SA1812T100Q ROHM Semiconductor	TRANS PNP 400V 0.5A SOT-89	0
	2SD1857ATV2Q ROHM Semiconductor	TRANS NPN 160V 1.5A ATV	0
	2SC4115STPR ROHM Semiconductor	TRANS NPN 20V 2A SPT	0
	2SA1807TLP ROHM Semiconductor	TRANS PNP 600V 1A TO252	0
	2SD1863TV2R ROHM Semiconductor	TRANS NPN 80V 1A ATV	0
	2SD1857ATV2P ROHM Semiconductor	TRANS NPN 160V 1.5A ATV	0
	2SD2144STPU ROHM Semiconductor	TRANS NPN 20V 0.5A 3PIN 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