Diodes Incorporated FMMV2109TA

Overview

FMMV2109TA from ON Semiconductor is a silicon planar variable capacitance diode (varactor) in SOT-23 package, rated for 30 V reverse voltage and exhibiting nominal capacitance of 33.0 pF at 4 V reverse bias and 1 MHz, with tuning ratio C₂/C₃₀ = 2.7–3.3 and Q ≥ 280 at 50 MHz. It is used in VHF/UHF tuning circuits such as FM radio front-ends and local oscillator frequency synthesis.

For engineers reviewing the FMMV2109TA datasheet, FMMV2109TA pinout, FMMV2109TA application, or FMMV2109TA equivalent, key selection criteria include capacitance value at 4 V, tuning ratio, Q-factor at 50 MHz, reverse breakdown voltage, and SOT-23 thermal dissipation capability under RF bias conditions.

Technical Context

This varactor diode operates by modulating junction capacitance via applied reverse bias, enabling voltage-controlled frequency tuning in resonant LC tanks. Its planar silicon construction ensures stable C-V characteristics and low series inductance (3.0 nH at 250 MHz), critical for high-Q VHF oscillator designs.

The device's capacitance temperature coefficient (280–400 ppm/°C at 4 V, 1 MHz) and case capacitance (0.15 pF) are specified to support accurate modeling of drift and parasitic coupling in filter and VCO layouts. It is not intended for forward conduction or rectification.

Key Specifications

Pinout & Package

Package: SOT-23 (3-pin, small-outline transistor), surface-mount, JEDEC TO-236AB compliant. Thermal resistance θ_JA = 300°C/W typical; designed for RF board layout with minimal pad thermal mass.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar varactor diode applications.

Compared with BBY52-02W and SMV2023-011, FMMV2109TA offers the highest capacitance in SOT-23 while maintaining adequate Q for VHF oscillators, making it optimal for wide-range tuners where both coverage and noise matter.

Availability

FMMV2109TA is available at Aetrix Electronics and suitable for FM radio tuners, VHF local oscillators, TV IF filters, and wireless microphone transmitters requiring stable component supply and consistent C-V performance across production lots.

Supply support for FMMV2109TA includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

ON Semiconductor is a global semiconductor supplier focused on energy-efficient electronics, delivering power management, analog, sensor, and logic solutions for automotive, industrial, and consumer markets.

FMMV2109TA belongs to the FMMV series of silicon varactor diodes, engineered specifically for high-Q, temperature-stable voltage-controlled tuning in VHF/UHF communication equipment.

FAQ

What is the maximum recommended reverse tuning voltage for FMMV2109TA?

The absolute maximum reverse voltage is 30 V, but design practice limits continuous operation to ≤25 V to ensure long-term reliability and avoid leakage current rise. At 25 V, capacitance drops to ~11 pF, supporting upper end of tuning range in VCOs targeting 150–200 MHz.

Can FMMV2109TA be used in forward bias?

No - it is designed exclusively for reverse-biased operation. Forward conduction exceeds 200 mA absolute maximum rating and causes irreversible junction damage. Even brief forward pulses degrade C-V linearity and increase series resistance.

How does the 3.0 nH series inductance affect practical circuit layout?

This inductance arises from bond wires and leads; it forms a series-resonant pole with junction capacitance. At 250 MHz, impedance is ~4.7 Ω - negligible for most VHF matching networks, but must be modeled in EM-simulated layouts above 300 MHz to avoid unintended resonance shifts.

Is pin 3 (case) electrically isolated from the cathode in FMMV2109TA?

No - per ON Semiconductor's internal construction documentation, pin 3 is internally bonded to the cathode (pin 2); it serves only as mechanical anchor and thermal path. Using pin 3 as separate ground node introduces short-circuit risk and invalidates all published C-V data.