Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
2SC3649T-TD-H Sanyo Semiconductor/ON Semiconductor	TRANS NPN 160V 1.5A PCP	2147483647
FSB649 Sanyo Semiconductor/ON Semiconductor	TRANS NPN 25V 3A SUPERSOT3	566
BF199RL1	SMALL SIGNAL BIPOLAR TRANSISTOR	4000
2N2896 Roving Networks / Microchip Technology	BJTS	0
BCX51H6327XTSA1 IR (Infineon Technologies)	TRANS PNP 45V 1A SOT89	58493
DSC700400L Panasonic	TRANS NPN 50V 2A MINIP3	638
MMBT6427LT1G Sanyo Semiconductor/ON Semiconductor	TRANS NPN DARL 40V 500MA SOT23-3	1088
KSP44TF Sanyo Semiconductor/ON Semiconductor	TRANS NPN 400V 300MA TO92-3	0
2PB710AS,115 NXP Semiconductors	TRANS PNP 50V 500MA SMT3	9000
NTE342 NTE Electronics, Inc.	T-NPN RF PO 7W TYP TO-220 TYPE	634
2N3417 NTE Electronics, Inc.	TRANS NPN 50V 500MA TO92-3	0
BC550CTA Sanyo Semiconductor/ON Semiconductor	TRANS NPN 45V 0.1A TO-92	0
2SB647CTZ-E Renesas Electronics America	SMALL SIGNAL BIPOLAR TRANS PNP	3527
KST64MTF	TRANS PNP 30V 500MA SOT23-3	21145
2STN1550 STMicroelectronics	TRANS NPN 50V 5A SOT-223	31829
BC847BW Diotec Semiconductor	BJT SOT-323 45V 100MA	0
2N2605 Roving Networks / Microchip Technology	TRANS PNP 60V 0.03A TO-46	0
MPS6724G	TRANS NPN 40V 1A TO92	3000
2SD1841Q	POWER BIPOLAR TRANSISTOR NPN	616
2SC3467E-AE	SMALL SIGNAL BIPOLAR TRANSTR NPN	24000

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