Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
PZT4403,115 Nexperia	TRANS PNP 40V 600MA SOT223	14
BCX70K IR (Infineon Technologies)	TRANS NPN 45V 200MA SOT23-3	3230
SBC807-25LT1	SMALL SIGNAL BIPOLAR TRANSISTOR	33000
MJD44H11AJ Nexperia	TRANS NPN 80V 8A DPAK	1268
PZT2907A	0.8A, 60V, PNP, TO-261AA	29416
MJE800STU	POWER BIPOLAR TRANSISTOR	817
KSP2222ATA	SMALL SIGNAL BIPOLAR TRANSISTOR,	203739
PBHV9040T,215 Nexperia	TRANS PNP 400V 0.25A SOT23-3	13453
2SA1417T-TD-E Sanyo Semiconductor/ON Semiconductor	TRANS PNP 100V 2A SOT89-3	1199
2SC5824T100Q ROHM Semiconductor	TRANS NPN 60V 3A SOT-89	1435
FZT653TA Zetex Semiconductors (Diodes Inc.)	TRANS NPN 100V 2A SOT-223	75688
KST5551MTF	0.6A, 160V, NPN	53000
PBSS303PD,115 Nexperia	TRANS PNP 60V 1A 6TSOP	3000
PHPT60606PYX Nexperia	TRANS PNP BIPO 60V 6A 8LFPAK	0
2SA1576AT106Q ROHM Semiconductor	TRANS PNP 50V 0.15A SOT-323	843
BUL42D	POWER BIPOLAR TRANSISTOR NPN	2500
BC817K-25HR Nexperia	BC817 - 45 V, 500 MA NPN GENERAL	2043000
2STW200 STMicroelectronics	TRANS PNP DARL 80V 25A TO-247	265
MJL3281AG Sanyo Semiconductor/ON Semiconductor	TRANS NPN 260V 15A TO264	0
TSA874CW RPG TSC (Taiwan Semiconductor)	TRANSISTOR, PNP, -500V, -0.15A,	0

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