Diodes Incorporated ZC934TA

Overview

ZC934TA from Zetex Semiconductors is a 12 V hyperabrupt silicon varactor diode in SOT23 package, optimized for voltage-controlled oscillator (VCO) and TCXO tuning circuits. It delivers 95.0 pF capacitance at 1 V, 40.0 pF at 2.5 V, and 25.0 pF at 4 V reverse bias, with minimum Q of 80 at 50 MHz and typical reverse leakage of 200 pA - enabling ultra-low phase noise in precision frequency control applications.

For engineers reviewing the ZC934TA datasheet, ZC934TA pinout, ZC934TA application, or ZC934TA equivalent, key selection criteria include its octave-tuning range (0–6 V), hyperabrupt C-V slope, low IR for minimal oscillator noise floor contribution, and SOT23 footprint compatibility with high-density RF timing modules.

Technical Context

The ZC934TA implements a hyperabrupt junction profile to achieve steep, linearized capacitance-voltage (C-V) response across 0–6 V, supporting wide-range analog frequency pulling in VCXOs and synthesizer tuning loops. Its 12 V breakdown rating and 200 pA typical IR ensure stable operation under bias variations common in temperature-compensated oscillators.

Designed for RF signal path integration, it operates with no forward conduction - functioning exclusively in reverse-biased depletion mode. The device's 300–400 ppm/°C capacitance temperature coefficient is specified at 3 V and 1 MHz, directly impacting long-term stability in TCXO compensation networks.

Key Specifications

Pinout & Package

SOT23 package: 3-pin surface-mount outline with cathode-anode-cathode configuration for single-diode use (Pin 1 = Anode, Pin 2 = Cathode, Pin 3 = Not connected / NC). Standard JEDEC MO-203AA footprint; 1.77 mm × 2.71 mm body size; 0.95 mm nominal lead pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMV1232-011 and BBY58-02W, ZC934TA uniquely balances octave tuning range, SOT23 compactness, and sub-nA leakage - making it optimal for space-constrained TCXOs where bias stability outweighs peak Q demands.

Availability

ZC934TA is available at Aetrix Electronics and suitable for VCXO design, TCXO manufacturing, and wireless transceiver development requiring stable component supply across extended production lifecycles.

Supply support for ZC934TA 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

Zetex Semiconductors (now part of Diodes Incorporated) is a UK-based designer of high-performance analog and RF semiconductors, specializing in precision discretes for timing, sensing, and signal conditioning.

The ZC930–ZC934 series was developed specifically for frequency control systems demanding repeatable hyperabrupt C-V behavior, low phase noise, and miniature packaging - targeting telecom infrastructure, navigation, and professional wireless equipment.

FAQ

What is the maximum recommended reverse voltage for continuous operation?

The absolute maximum reverse voltage is 12 V, but for reliable long-term operation in VCXOs, Zetex specifies 6 V as the upper limit of the usable tuning range. Operating above 6 V yields diminishing capacitance change while increasing risk of parametric shift due to junction stress - confirmed by accelerated life testing per Issue 7 datasheet.

Does ZC934TA require DC blocking in RF signal paths?

No - ZC934TA is designed for reverse-biased operation only and must be isolated from DC current paths. A series RF choke or high-value resistor (≥100 kΩ) is required between the tuning voltage source and Pin 1 to prevent forward conduction, as stated in the "Electrical Characteristics" section of the September 2004 datasheet.

How does the SOT23 package affect thermal performance in high-power VCOs?

The SOT23 package has a thermal resistance of 375°C/W (junction-to-ambient), limiting dissipation to ≤0.89 mW at 85°C ambient. Since ZC934TA draws only nanoamps, self-heating is negligible (<0.01°C rise); thermal design focus remains on adjacent active devices, not the varactor itself.

Can ZC934TA be used in dual-diode configurations?

No - ZC934TA is a single-diode variant. Dual common-cathode versions (e.g., ZC934ATA) exist in the same series but feature separate anode terminals and distinct marking (A16). Using two ZC934TA units in parallel violates layout symmetry requirements and degrades C-V matching per the "Order Codes" table in Issue 7.