Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
NTE185 NTE Electronics, Inc.	TRANS PNP 80V 4A TO126	355
MMBT2222A NTE Electronics, Inc.	T-NPN SI- GEN PUR AMP	5794
BCW61C NTE Electronics, Inc.	T-PNP SI- GEN PUR	2262
MMBT2907A NTE Electronics, Inc.	T-PNP SI- GEN PUR AMP	6546
NTE226 NTE Electronics, Inc.	TRANS PNP 35V 2A TO66	221
2N6385 NTE Electronics, Inc.	TRANS NPN 80V 10A TO204AA	234
NTE281 NTE Electronics, Inc.	TRANS PNP 140V 12A TO3	204
NTE327 NTE Electronics, Inc.	TRANS NPN 150V 25A TO3	58
2N3584 NTE Electronics, Inc.	TRANS NPN 250V 2A TO66	277
TIP141 NTE Electronics, Inc.	TRANS DARLINGTON NPN 80V 10A	1140
NTE307 NTE Electronics, Inc.	TRANS PNP 40V 1.5A TO202	455
NTE185MCP NTE Electronics, Inc.	TRANS PNP 80V 4A TO126	15
2N5428 NTE Electronics, Inc.	TRANS NPN 80V 7A TO66	52
NTE182 NTE Electronics, Inc.	TRANS NPN 60V 10A TO127	0
NTE391 NTE Electronics, Inc.	TRANS PNP 100V 10A TO3PN	90
NTE181 NTE Electronics, Inc.	TRANS NPN 100V 30A TO3	651
NTE193 NTE Electronics, Inc.	TRANS PNP 50V 500MA TO92HS	170
NTE289A NTE Electronics, Inc.	TRANS NPN 80V 500MA TO92	425
2N3906 NTE Electronics, Inc.	SMALL SIGNAL BIPOLAR TRANSISTOR	224461
NTE2320 NTE Electronics, Inc.	TRANS NPN 30V 500MA 14DIP	95

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