Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - Single

Part Number	Description / PDF	Quantity
BC69-25PASX Nexperia	BC69PAS - 20 V, 2 A PNP MEDIUM	5035
MMBTA14LT1HTSA1 IR (Infineon Technologies)	TRANSISTOR NPN DARL 30V 0.3A	53750
MMBTA94 Diotec Semiconductor	BJT SOT-23 400V 300MA	0
DTC124E	TRANS DIGITAL BJT NPN 50V 100MA	0
MPSA05RA Sanyo Semiconductor/ON Semiconductor	TRANS NPN 60V 500MA TO92-3	0
2N5550TF	TRANS NPN 140V 600MA TO92-3	48424
2SD1803T-E Sanyo Semiconductor/ON Semiconductor	TRANS NPN 50V 5A TP	427
2SB906-Y(TE16L1,NQ Toshiba Electronic Devices and Storage Corporation	TRANS PNP 60V 3A PW-MOLD	1814
MJE182 NTE Electronics, Inc.	GENERAL PURPOSE NPN TRANSISTOR	9552
BCW68GE6327HTSA1 IR (Infineon Technologies)	TRANS PNP 45V 0.8A SOT-23	0
BCX70KT216 ROHM Semiconductor	TRANS NPN 45V 0.2A SST3	0
MJL1302AG Sanyo Semiconductor/ON Semiconductor	TRANS PNP 260V 15A TO264	0
FJPF3305TU	TRANS NPN 400V 4A TO220F	26153
MJE4353 NTE Electronics, Inc.	TRANS PNP 160V 16A TO218	760
KSD1621TTF	TRANS NPN 25V 2A SOT89-3	56000
MJE200	TRANS NPN 40V 5A TO225AA	0
PN2907ATFR Sanyo Semiconductor/ON Semiconductor	TRANS PNP 60V 800MA TO92-3	0
BC860C,215 Nexperia	TRANS PNP 45V 100MA TO236AB	9578
2SB1382 Sanken Electric Co., Ltd.	TRANS PNP DARL 120V 16A TO3PF	372
BC560C	TRANS PNP 45V 100MA TO92-3	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