Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
2SA1860 Sanken Electric Co., Ltd.	TRANS PNP 150V 14A TO-3PF	1779
2N3501 Roving Networks / Microchip Technology	TRANS NPN 150V 0.3A TO-39	1
2SA2127-AE	2SA2127 - PNP BIPOLAR TRANSISTOR	26999
BC239BBU	TRANS NPN 25V 100MA TO92-3	7021
ZXTN4000ZTA Zetex Semiconductors (Diodes Inc.)	TRANS NPN 60V 1A SOT89	145742000
CMPT3646 TR PBFREE Central Semiconductor	TRANS NPN 40V 0.2A SOT23	6887
2N3702	SMALL SIGNAL BIPOLAR TRANSISTOR	41005
2PD601ASL,215 Nexperia	TRANS NPN 50V 100MA TO236AB	0
2N5308 PBFREE Central Semiconductor	TRANS NPN DARL 40V 0.3A TO-92	2214
DSS4240Y-7 Zetex Semiconductors (Diodes Inc.)	TRANS NPN 40V 2A SOT363	0
2SA2088U3T106 ROHM Semiconductor	2SA2088U3 IS THE HIGH SPEED SWIT	0
2N6384 Roving Networks / Microchip Technology	NPN TRANSISTOR	0
MPS3563RLRAG	SMALL SIGNAL BIPOLAR TRANSISTOR	6000
MMBTA05-HF Comchip Technology	TRANS NPN 60V 0.5A SOT-23	3000
BCX19LT1	TRANS NPN 45V 500MA SOT23-3	73000
BC856A-7-F Zetex Semiconductors (Diodes Inc.)	TRANS PNP 65V 0.1A SOT23-3	1141963000
2SARA41CT116R ROHM Semiconductor	HIGH-VOLTAGE AMPLIFIER TRANSISTO	2580
BC857BT116 ROHM Semiconductor	TRANS PNP 45V 0.1A SST3	1001
ZXTP25020BFHTA Zetex Semiconductors (Diodes Inc.)	TRANS PNP 20V 4A SOT23-3	3909
2SD2390 Sanken Electric Co., Ltd.	TRANS NPN DARL 150V 10A TO-3P	326

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