Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
2SC39390RA Panasonic	TRANS NPN 80V 0.5A TO-92NL	494
DSC7505Q0L Panasonic	TRANS NPN 20V 3A MINIP3	961
DSC2C01R0L Panasonic	TRANS NPN 100V 0.02A MINI3	33
2SD05920RA Panasonic	TRANS NPN 25V 1A TO-92	4038
2SA1791GRL Panasonic	TRANS PNP 50V 0.05A SSMINI-3	6
DSC2001Q0L Panasonic	TRANS NPN 50V 0.1A MINI3-G3-B	1857
2SD14500RA Panasonic	TRANS NPN 20V 0.5A NS-B1	4919
DSC2A01S0L Panasonic	TRANS NPN 40V 0.05A MINI3	2890
2SA2028G0L Panasonic	TRANS PNP 20V 1A SMINI-3	5671
2SD21330RA Panasonic	TRANS NPN 50V 1A MT-3	1528
DSC5G02D0L Panasonic	TRANS NPN 20V 0.015A SMINI3	0
DSA7506R0L Panasonic	TRANS PNP 25V 3A MINIP3	0
DSC5G03S0L Panasonic	TRANS NPN 20V 0.05A SMINI3	0
DSC5G02C0L Panasonic	TRANS NPN 20V 0.015A SMINI3	0
DSC5G03T0L Panasonic	TRANS NPN 20V 0.05A SMINI3	0
DSA3G0100L Panasonic	TRANS PNP 20V 0.03A SSSMINI3	0
DSC5501T0L Panasonic	TRANS NPN 20V 0.5A SMINI3	0
2SC18460S Panasonic	TRANS NPN 35V 1A TO-126	0
2SD22580RA Panasonic	TRANS NPN DARL 50V 1A MT-2	0
2SB1218A0L Panasonic	TRANS PNP 45V 0.1A SMINI 3P	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