Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
CMPT6517 TR PBFREE Central Semiconductor	TRANS NPN 350V 0.5A SOT-23	21066
CZT3904 TR PBFREE Central Semiconductor	TRANS NPN 40V 0.2A SMT	370
2N2904A PBFREE Central Semiconductor	TRANS PNP 60V 0.6A TO-39	628
MPS3415 TIN/LEAD Central Semiconductor	TRANS NPN 25V 0.5A TO-92	0
2N4401 PBFREE Central Semiconductor	TRANS NPN 40V 0.6A TO-92	11407
2N6426 PBFREE Central Semiconductor	THROUGH-HOLE TRANSISTOR-SMALL SI	0
CMUT5087E TR PBFREE Central Semiconductor	TRANS PNP 50V 0.1A SOT523	4590
CP127-2N6301-CT5 Central Semiconductor	TRANS NPN 1=5PCS	13
CMPT5086 TR PBFREE Central Semiconductor	TRANS PNP 50V 50MA SOT23	0
2N3501 PBFREE Central Semiconductor	TRANS NPN 150V 0.3A TO-39	0
2N3700 PBFREE Central Semiconductor	THROUGH-HOLE TRANSISTOR-SMALL SI	0
CJD200 TR13 Central Semiconductor	TRANS NPN 40V 5A DPAK	2500
2N5367 PBFREE Central Semiconductor	THROUGH-HOLE TRANSISTOR-SMALL SI	0
CJD122 TR13 Central Semiconductor	TRANS NPN 100V 8A DPAK	0
CEN-U05 PBFREE Central Semiconductor	TRANS NPN 60V 2A TO202	785
CMST5089 TR PBFREE Central Semiconductor	TRANS NPN 30V 50MA SOT323	1524
2N4234 PBFREE Central Semiconductor	TRANS PNP 40V 1A TO-39	0
CJD47 TR13 PBFREE Central Semiconductor	TRANS NPN 350V 1A DPAK	1298
CMPT3904G TR PBFREE Central Semiconductor	TRANS NPN 40V 0.2A SOT-23	0
CMPT4403 TR PBFREE Central Semiconductor	TRANS PNP 40V 0.6A SOT-23	11793

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