Diodes - Variable Capacitance (Varicaps, Varactors)

Part Number	Description / PDF	Quantity
1SV311(TPH3,F) Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 10V ESC	0
1SV323,H3F Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 10V ESC	3526
1SV279,H3F Toshiba Electronic Devices and Storage Corporation	PB-F ESC VARICAP DIODE (HF), IR=	0
1SV281(TPH3,F) Toshiba Electronic Devices and Storage Corporation	DIODE VCO V/UHF 10V ESC	22194
1SV229TPH3F Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 15V USC	0
1SV228TPH3F Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR DUAL 15V SC-59	33
1SV285TPH3F Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 10V ESC	0
1SV280,H3F Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 15V ESC	82151
1SV282TPH3F Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 34V SINGLE ESC	87
1SV277TPH3F Toshiba Electronic Devices and Storage Corporation	DIODE VARICAP VCO UHF USC	0
1SV325,H3F Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 10V ESC	0
1SV305,L3F Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 10V ESC	15813
1SV324TPH3F Toshiba Electronic Devices and Storage Corporation	DIODE TCXO/VCO 10V USC	3000
1SV310TPH3F Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 10V USC	0
1SV304TPH3F Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 10V USC	1822
1SV270TPH3F Toshiba Electronic Devices and Storage Corporation	DIODE VARICAP VCO UHF USC	0
1SV239TPH3F Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 15V USC	11459
1SV314(TPL3,F) Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 10V SINGLE ESC	0
1SV305,H3F Toshiba Electronic Devices and Storage Corporation	DIODE VARACTOR 10V ESC	0

Diodes - Variable Capacitance (Varicaps, Varactors)

1. Overview

Variable Capacitance Diodes (Varicaps or Varactors) are specialized semiconductor devices that exploit the voltage-dependent capacitance of a reverse-biased p-n junction. These components act as voltage-controlled capacitors, enabling electronic tuning and frequency modulation in various circuits. Their ability to provide precise capacitance adjustment without mechanical movement makes them critical in modern communication systems, signal processing, and RF/wireless applications.

2. Main Types and Functional Classification

Type	Functional Characteristics	Application Examples
Hyperabrupt Varactors	Non-linear C-V curve with high capacitance ratio	Voltage-Controlled Oscillators (VCOs), Frequency Synthesizers
Abrupt Junction Varactors	Linear C-V characteristics	Parametric Amplifiers, Tunable Filters
Double Varactors	Dual back-to-back junctions for balanced operation	Modulators, Demodulators, Microwave Switches
High-Voltage Varactors	Rated for >100V reverse bias	Power Tuning Circuits, Industrial RF Equipment

3. Structure and Composition

Varactors are constructed with a p-n junction optimized for controlled depletion region expansion. Key structural elements include:

Doped semiconductor layers (typically silicon or GaAs)
Metallized contacts with passivation layers
Hermetic glass or plastic encapsulation
Specific junction geometry to define capacitance-voltage (C-V) characteristics

The depletion region width varies with reverse bias voltage, altering the effective capacitance according to the formula: C = A/(W+d), where W is depletion width and d is fixed dielectric thickness.

4. Key Technical Specifications

Parameter	Significance
Capacitance Range (Cmin-Cmax)	Determines tuning range at specific bias voltages
Q-Factor (Quality Factor)	Measures energy loss at operating frequencies
Breakdown Voltage (Vbr)	Maximum allowable reverse voltage
Series Resistance (Rs)	Affects power handling capability
Temperature Coefficient	Defines capacitance stability over temperature
Capacitance Ratio (Cmax/Cmin)	Indicates tuning efficiency

5. Application Fields

Major application areas include:

Telecommunications: Cellular base stations, Satellite receivers, Wi-Fi equipment
Consumer Electronics: Smartphones, Television tuners, Bluetooth devices
Industrial: Test and measurement equipment, RFID systems
Automotive: Keyless entry systems, Radar sensors
Specialized: Phase-locked loops (PLLs), Parametric amplifiers

Case Study: In a smartphone transceiver, varactors enable adaptive antenna tuning to maintain optimal signal strength across multiple frequency bands (700MHz-6GHz).

6. Leading Manufacturers and Products

Manufacturer	Product Series	Key Features
ON Semiconductor	MVAM Series	High Q (>1000), 12pF-50pF range
STMicroelectronics	BB8XX Series	Ultra-small SMD packaging, 1-30pF
Skyworks Solutions	SMV Series	High linearity for CATV applications
NXP Semiconductors	BBY Series	Automotive-grade temperature stability

7. Selection Guidelines

Key selection criteria:

Match capacitance range to required frequency tuning range
Select appropriate Q-factor for target frequency (higher Q for microwave applications)
Consider temperature stability requirements
Evaluate package type (SMD vs. through-hole) for PCB integration
Verify voltage ratings against circuit requirements
Assess non-linearity requirements for modulation applications

For high-reliability applications, prioritize devices with AEC-Q101 automotive qualification.

8. Industry Trends

Current development trends include:

Increased integration with MEMS technology for hybrid tuning solutions
Development of GaN-based varactors for millimeter-wave applications
Improved capacitance ratios through advanced junction engineering
Nanometer-scale dielectrics for ultra-low voltage operation
Embedded varactors in SiP (System-in-Package) modules

The market is projected to grow at 6.2% CAGR through 2027, driven by 5G infrastructure and IoT connectivity demands.