Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
2SA2161J0L Panasonic	TRANS PNP 12V 0.5A SSMINI3P	3344
2SD1820G0L Panasonic	TRANS NPN 50V 0.5A SMINI-3	3907
DSA7U01Q0L Panasonic	TRANS PNP 100V 0.5A MINIP3	960
DSC2A01T0L Panasonic	TRANS NPN 40V 0.05A MINI3	47825
2SB1219GSL Panasonic	TRANS PNP 50V 0.5A SMINI-3	5635
2SD145000A Panasonic	TRANS NPN 20V 0.5A NS-B1	3673
2SD2413G0L Panasonic	TRANS NPN 400V 0.1A MINIP-3	2867
2SC24050RL Panasonic	TRANS NPN 35V 0.05A MINI-3P	2666
2SD250400A Panasonic	TRANS NPN 10V 5A TO-92	1219
2SC5946G0L Panasonic	TRANS NPN 20V 0.05A SSSMINI-3	2251
2SA201000L Panasonic	TRANS PNP 15V 2.5A MINI 3P	5220
DSC2501R0L Panasonic	TRANS NPN 20V 0.5A MINI3	6081
2SB1218AQL Panasonic	TRANS PNP 45V 0.1A SMINI 3P	14624
2SA16740SA Panasonic	TRANS PNP 80V 1A MT-2	2551
DSA940200L Panasonic	TRANS PNP 12V 0.5A SSMINI3	2982
2SB15990QL Panasonic	TRANS PNP 40V 1.5A MINI PWR	2178
DSC500200L Panasonic	TRANS NPN 50V 0.5A SMINI	38
2SB169300L Panasonic	TRANS PNP 20V 0.5A MINI-3	4786
2SB1320A0A Panasonic	TRANS PNP 50V 0.1A MT-1	9015
2SC441000L Panasonic	TRANS NPN 7V 0.01A SMINI-3	2282

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