Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
NTE2342 NTE Electronics, Inc.	TRANS PNP 80V 1A TO92	363
NTE2309 NTE Electronics, Inc.	TRANS NPN 800V 12A TO3P	75
NTE2429 NTE Electronics, Inc.	TRANS PNP 80V 1A SOT89	1554
TIP126 NTE Electronics, Inc.	POWER BIPOLAR TRANSISTOR, PNP	7312
2N404A NTE Electronics, Inc.	TRANS PNP 35V 150MA TO5	217
2N4401 NTE Electronics, Inc.	T-NPN SI-GEN PUR AMP SW	1550
NTE2312 NTE Electronics, Inc.	TRANS NPN 400V 8A TO220	546
NTE87 NTE Electronics, Inc.	TRANS NPN 250V 10A TO3	972
NTE175 NTE Electronics, Inc.	TRANS NPN 300V 2A TO66	258
NTE213 NTE Electronics, Inc.	TRANS PNP 60V 30A TO36	16
NTE274 NTE Electronics, Inc.	TRANS NPN 80V 4A TO66	519
MMBT3904 NTE Electronics, Inc.	TRANS NPN 40V 200MA SOT23-3	4036
NTE297MP NTE Electronics, Inc.	TRANS NPN 80V 500MA TO92	8
NTE2427 NTE Electronics, Inc.	TRANS PNP 80V 500MA SOT89	2233
2N3773 NTE Electronics, Inc.	TRANS NPN 140V 16A TO204	334
2N6426 NTE Electronics, Inc.	TRANS NPN 40V 500MA TO92-3	778
2N5192 NTE Electronics, Inc.	TRANS NPN 80V 4A TO225AA	17
NTE256 NTE Electronics, Inc.	TRANS NPN 400V 28A TO218	156
PN2907A NTE Electronics, Inc.	TRANS PNP 60V 600MA TO92-3	589
2N5551 NTE Electronics, Inc.	SMALL SIGNAL BIPOLAR TRANSISTOR	34000

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