Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
BC557B	TRANS PNP 45V 100MA TO92-3	9312
MJE170STU	POWER BIPOLAR TRANSISTOR	6100
MPS6727	TRANS PNP 40V 1A TO92	3968
CZT2907A TR PBFREE Central Semiconductor	TRANS PNP 60V 0.6A SOT223	482
BC858BWE6327 IR (Infineon Technologies)	BIPOLAR GEN PURPOSE TRANSISTOR	66000
FJN3301RTA	0.1A, 50V, NPN, TO-92	52261
NJVTIP31CG	BIP TO-220 NPN 3A 100V	10920
2N6308 Roving Networks / Microchip Technology	NPN TRANSISTOR	0
BD180G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 80V 1A TO225AA	15887000
MMBT2222AT-7-F Zetex Semiconductors (Diodes Inc.)	TRANS NPN 40V 0.6A SOT523	2147483647
PBSS5250X146 NXP Semiconductors	SMALL SIGNAL BIPOLAR TRANSISTOR	0
PMST6429,115 NXP Semiconductors	NOW NEXPERIA PMST6429 - SMALL SI	941930
KSD526OTU	TRANS NPN 80V 4A TO220-3	0
2SCR574DGTL ROHM Semiconductor	TRANS NPN 80V 2A	0
MMBT3906LT3G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 40V 200MA SOT23-3	16599
MJF122G Sanyo Semiconductor/ON Semiconductor	TRANS NPN DARL 100V 5A TO220FP	1273
2SC3576	SMALL SIGNAL BIPOLAR TRANSTR NPN	35650
BCW72LT1G Sanyo Semiconductor/ON Semiconductor	TRANS NPN 45V 100MA SOT23-3	4589
2SA1586-Y,LF Toshiba Electronic Devices and Storage Corporation	TRANS PNP 50V 0.15A USM	43
NSVBC857CWT1G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 45V 0.1A SOT-323	810796000

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