Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
2N4923 PBFREE Central Semiconductor	TRANS NPN 80V 1A TO-126	286
FCX658ATA Zetex Semiconductors (Diodes Inc.)	TRANS NPN 400V 0.5A SOT-89	42551
2SD1383KT146B ROHM Semiconductor	TRANS NPN DARL 32V 0.3A SOT-346	213
BC807-25LT1G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 45V 500MA SOT23-3	15877
SPZT3904T1G Sanyo Semiconductor/ON Semiconductor	TRANS NPN 40V 200MA SOT223-3	3461
NSV20101JT1G	SMALL SIGNAL BIPOLAR TRANSISTOR,	66000
2SAR533P5T100 ROHM Semiconductor	PNP -50V -3A MEDIUM POWER TRANSI	73
NTE72 NTE Electronics, Inc.	TRANS NPN 80V 10A TO61	8
BCR191WH6327 IR (Infineon Technologies)	BIPOLAR DIGITAL TRANSISTOR	9000
NTE2330 NTE Electronics, Inc.	TRANS NPN 55V 4A TO3P	195
2N5884 NTE Electronics, Inc.	TRANS PNP 80V 25A TO3	4759
2N6109G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 50V 7A TO220AB	3579250
CMNT3904E TR PBFREE Central Semiconductor	TRANS NPN 60V 0.2A SOT953	224000
2SB1228	PNP DARLINGTON TRANSISTOR	2657
BCX71K,215 Nexperia	TRANS PNP 45V 100MA TO236AB	503
2DD1766R-13 Zetex Semiconductors (Diodes Inc.)	TRANS NPN 32V 2A SOT89-3	9997500
BC556	TRANS PNP 65V 100MA TO92-3	16860
BCX53-16,146 Nexperia	TRANS PNP 80V 1A SOT89	0
PBSS4021NT/WD215 NXP Semiconductors	SMALL SIGNAL BIPOLAR TRANSISTOR	576000
BC559B	TRANS PNP 30V 100MA TO92-3	1740

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