Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Image	Part Number	Description / PDF	Quantity	Rfq
	2N6251T1 Microsemi	NPN TRANSISTOR	0
	2C5014 Microsemi	TRANSISTOR NPN TO-5	0
	JANTX2N6251T1 Microsemi	TRANS NPN 350V 10A TO-3	0
	2N2221AL Microsemi	TRANS NPN 50V 0.8A TO18	0
	JANTX2N6249 Microsemi	TRANS NPN 200V 10A TO-3	0
	JANS2N6251T1 Microsemi	TRANS NPN 350V 10A TO-3	0
	JAN2N1489 Microsemi	TRANS NPN 40V 6A	0
	JAN2N6249 Microsemi	TRANS NPN 200V 10A TO-3	0
	JANTXV2N2221AUA Microsemi	TRANS NPN 50V 0.8A	0
	JANTX2N3019/TR Microsemi	SMALL-SIGNAL BJT	0
	JANTX2N3251AUB Microsemi	TRANS PNP 60V 0.2A TO-39	0
	JAN2N3251AUB Microsemi	TRANS PNP 60V 0.2A TO-39	0
	2N3251AUB Microsemi	TRANS PNP 60V 0.2A	0
	2C5015 Microsemi	TRANSISTOR NPN TO-5	0
	JAN2N1016B Microsemi	TRANS NPN 100V 7.5A	0
	JANTX2N6250T1 Microsemi	TRANS NPN 275V 10A TO-3	0
	JAN2N2221AUA Microsemi	TRANS NPN 50V 0.8A	0
	JANS2N6250T1 Microsemi	TRANS NPN 275V 10A TO-3	0
	JANTXV2N3960UB Microsemi	TRANS NPN 12V UB	0
	2N2944AUB Microsemi	TRANS PNP 10V 0.1A	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