Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
KSC838YTA	TRANS NPN 30V 30MA TO92-3	0
DTC124ERLRA	SMALL SIGNAL BIPOLAR TRANSISTOR	8000
KSA643YTA	0.5A, 20V, PNP, TO-92	559693
2N4125RLRA	SMALL SIGNAL BIPOLAR TRANSISTOR	0
KSC2330RTA	TRANS NPN 300V 100MA TO92-3	1755
STN690A STMicroelectronics	TRANS NPN 30V 3A SOT223	0
2SA1797T100P ROHM Semiconductor	TRANS PNP 50V 2A SOT-89	5
BCX18LT1G	TRANS PNP 25V 500MA SOT23-3	33000
NTE153 NTE Electronics, Inc.	TRANS PNP 90V 4A TO220	320
BC856BLT1	TRANS PNP 65V 0.1A SOT23	561725
NJV4030PT3G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 40V 3A SOT223	0
2SD1803S-E Sanyo Semiconductor/ON Semiconductor	TRANS NPN 50V 5A TP	43114000
2SC3331S	SMALL SIGNAL BIPOLAR TRANSTR NPN	0
TIP41C STMicroelectronics	TRANS NPN 100V 6A TO-220	1050
BCX51-10,115 Nexperia	TRANS PNP 45V 1A SOT89	111
PBSS5240X115 NXP Semiconductors	SMALL SIGNAL BIPOLAR TRANSISTOR	82555
BC857BLP-7 Zetex Semiconductors (Diodes Inc.)	TRANS PNP 45V 0.1A 3-DFN	100
MPSA42G	TRANS NPN 300V 500MA TO92-3	0
BFN39E6327 IR (Infineon Technologies)	HIGH VOLTAGE BIPOLAR TRANSISTOR	9000
KSD1616YTA	TRANS NPN 50V 1A TO92-3	3831

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