Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
BCP55-10TF Nexperia	BCP55-10T/SOT223/SC-73	0
BCW70,235 Nexperia	NOW NEXPERIA BCW70 - SMALL SIGNA	30000
2PD602ASL,235 Nexperia	TRANS NPN 50V 0.5A SOT-23	0
PMBT3904QAZ Nexperia	PMBT3904QA/SOT1215/DFN1010D-3	0
BC847BQAZ Nexperia	NOW NEXPERIA BC847BQA - SMALL SI	164880
PHPT60410PYX Nexperia	TRANS PNP 40V 10A LFPAK56 PWRSO8	289
PBSS4240ZF Nexperia	TRANS NPN 40V 2A SOT223	3244
BCX55-16,115 Nexperia	TRANS NPN 60V 1A SOT89	7018
BSP62,115 Nexperia	TRANS PNP DARL 80V 1A SOT223	1146
BC807-16LZ Nexperia	BC807-16L/SOT23/TO-236AB	0
PBSS301PD,115 Nexperia	TRANS PNP 20V 4A 6TSOP	1436
BF821,235 Nexperia	TRANS PNP 300V 50MA TO236AB	6782
PMBT2222AQAZ Nexperia	PMBT2222AQA/SOT1215/DFN1010D-3	19918
BC55-10PASX Nexperia	BC55PAS - 60V, 1 A NPN MEDIUM PO	27000
PMBTA56,235 Nexperia	TRANS PNP 80V 500MA TO236AB	0
BCW68HVL Nexperia	BCW68HSOT23TO-236AB	7824
PBSS4240T,215 Nexperia	TRANS NPN 40V 2A TO236AB	1437
PBHV3160ZX Nexperia	IC TRANS PNP 600V 0.1A SOT223	791
PMBT4403Z Nexperia	TRANS PNP 40V 0.6A TO-236AB	0
BCX70H,215 Nexperia	TRANS NPN 45V 100MA TO236AB	20261

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