Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
BSV52,215 Nexperia	TRANS NPN 12V 100MA TO236AB	6
FZT951TC Zetex Semiconductors (Diodes Inc.)	TRANS PNP 60V 5A SOT223	4000
CZT955 TR PBFREE Central Semiconductor	TRANS PNP 140V 4A SOT-223	16353
MMBT3904-G Comchip Technology	TRANS NPN 40V 200MA SOT23	65930000
DSS5240T-7 Zetex Semiconductors (Diodes Inc.)	TRANS PNP 40V 2A SOT-23	397989
MMBTA42-AQ Diotec Semiconductor	BJT SOT-23 300V 500MA	0
MMBT3906LT1H	SMALL SIGNAL BIPOLAR TRANSISTOR	78000
2PC4617R,115 NXP Semiconductors	TRANS NPN 50V 150MA SC75	523599
2N4402RLRA	SMALL SIGNAL BIPOLAR TRANSISTOR	12333
BCP53TA Zetex Semiconductors (Diodes Inc.)	TRANS PNP 80V 1A SOT223-4	304
FZT649TC Zetex Semiconductors (Diodes Inc.)	TRANS NPN 25V 3A SOT223	0
2SC3325-Y,LF Toshiba Electronic Devices and Storage Corporation	TRANS NPN 50V 0.5A S-MINI	7382
ZXTN25100BFHTA Zetex Semiconductors (Diodes Inc.)	TRANS NPN 100V 3A SOT23-3	11882
FPN660A	TRANS PNP 60V 3A TO226	11565
2SC3646S-P-TD-E	BIPOLAR NPN TRANSISTOR, 1A 100V	5000
BC54-10PASX NXP Semiconductors	NOW NEXPERIA BC54-10PASX - SMALL	146990
FJD5304DTF Sanyo Semiconductor/ON Semiconductor	TRANS NPN 400V 4A DPAK	6690
FMMT491ATC Zetex Semiconductors (Diodes Inc.)	TRANS NPN 40V 1A SOT23-3	0
2SC3929ASL Panasonic	TRANS NPN 55V 0.05A SMINI-3	2687
2SA1416S-TD-E Sanyo Semiconductor/ON Semiconductor	TRANS PNP 100V 1A PCP	240610000

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