Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
ZXTN2007GTA Zetex Semiconductors (Diodes Inc.)	TRANS NPN 30V 7A SOT223	5592
2SD1782KT146Q ROHM Semiconductor	TRANS NPN 80V 0.5A SOT-346	8999
NSV2029M3T5G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 50V 0.15A SOT723	0
BC56-16PA-7 Zetex Semiconductors (Diodes Inc.)	TRANS NPN 80V 1A UDFN	4095
KSC2335RTU	TRANS NPN 400V 7A TO220-3	0
BC847A,235 NXP Semiconductors	NOW NEXPERIA BC847A - SMALL SIGN	280000
PHPT61002NYC115 NXP Semiconductors	POWER BIPOLAR TRANSISTOR, LFPAK	427000
BD237 STMicroelectronics	TRANS NPN 80V 2A SOT-32	1625
PBSS5350X,147 Nexperia	TRANS PNP 50V 3A SOT89	1880
BC857CLT1G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 45V 100MA SOT23-3	47333
BSP50	BSP50 - SMALL SIGNAL BIPOLAR TRA	1730
2N6546 Roving Networks / Microchip Technology	PNP TRANSISTOR	0
NSM80100MT1G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 80V 0.5A SC-74-6	0
FMMTA14TA Zetex Semiconductors (Diodes Inc.)	TRANS NPN DARL 40V 0.3A SOT23-3	0
PN2907TA	TRANS PNP 40V 800MA TO92-3	103841
BC238A	TRANS NPN 25V 100MA TO92-3	17128
PMST5550,135 Nexperia	TRANS NPN 140V 300MA SOT323	0
BC817-16QBZ Nexperia	BC817-16QB/SOT8015/DFN1110D-3	4950
NTE2349 NTE Electronics, Inc.	TRANS NPN 120V 50A TO3	234
2N3702 PBFREE Central Semiconductor	TRANS PNP 25V TO-92	5080

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