Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
2SD1618T-TD-E	0.7A, NPN	154850
SMMBTA92LT3G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 300V 0.5A SOT-23	0
KSC900GTA	TRANS NPN 25V 50MA TO92-3	12000
MJ21196G Sanyo Semiconductor/ON Semiconductor	TRANS NPN 250V 16A TO204	238
BC807-40WT1G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 45V 500MA SC70-3	2612
FCX491TA Zetex Semiconductors (Diodes Inc.)	TRANS NPN 60V 1A SOT-89	2147483647
2DC2412R-7 Zetex Semiconductors (Diodes Inc.)	TRANS NPN 50V 0.15A SOT23-3	0
BC517-D74Z Sanyo Semiconductor/ON Semiconductor	TRANS NPN DARL 30V 1.2A TO-92	0
MMBT3906 NTE Electronics, Inc.	T-PNP SI- GEN PUR AMP	2144
D42C11X	3A NPN POWER TRANSISTOR	3250
2SD1835S	SMALL SIGNAL BIPOLAR TRANSISTOR	12500
2SD1803T-TL-E Sanyo Semiconductor/ON Semiconductor	TRANS NPN 50V 5A TPFA	125416800
KSD1616LBU	TRANS NPN 50V 1A TO92-3	10000
MMBTA56Q-13-F Zetex Semiconductors (Diodes Inc.)	TRANS PNP 80V 0.5A SOT23-3	40000
KST4401MTF	0.6A, 40V, NPN	175841
BC327-025	TRANS PNP 45V 0.8A TO	19000
DSC900100L Panasonic	TRANS NPN 50V 0.1A SSMINI3	0
SBC857BWT1G Sanyo Semiconductor/ON Semiconductor	TRANS PNP 45V 0.1A SOT-323	9895
BC850C	SMALL SIGNAL BIPOLAR TRANSISTOR	3000
2SB1203S-TL-E Sanyo Semiconductor/ON Semiconductor	TRANS PNP 50V 5A TP-FA	1372

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