Diodes Incorporated ZC834ATC

Overview

ZC834ATC from Zetex Semiconductors is a silicon hyperabrupt varactor diode optimized for voltage-controlled frequency tuning in precision oscillators and RF filters. It delivers 42.3–51.7 pF capacitance at 2 V, 5.0–6.5 capacitance ratio (C₂/C₂₀), ≥200 Q at 50 MHz, ≤200 pA reverse leakage, and operates up to 25 V reverse bias - deployed in VCXO/TCXO modules requiring low phase noise and steep CV slope.

For engineers reviewing the ZC834ATC datasheet, ZC834ATC pinout, ZC834ATC application, or ZC834ATC equivalent, key selection criteria include its SOT23 package compatibility, hyperabrupt junction profile for high tuning linearity, 250 ppm/°C temperature coefficient of capacitance, and suitability for wireless transceiver VCOs where stable C-V slope and minimal IR-induced noise are critical.

Technical Context

The ZC834ATC implements a hyperabrupt p-n junction structure engineered to produce a steep, predictable capacitance-voltage (C-V) response - essential for narrow-band frequency pulling in crystal oscillator circuits. Its CV slope enables fine-grained tuning resolution without sacrificing Q-factor stability across 2–20 V reverse bias range.

Designed specifically for analog voltage-controlled tuning, it functions as a voltage-dependent capacitor with no active control logic or integrated bias circuitry. Its performance is characterized at 25°C ambient, with capacitance tolerance ±10% (A-grade), and specified reverse breakdown voltage ≥25 V - ensuring margin against transient overvoltage in oscillator tank networks.

Key Specifications

Pinout & Package

Supplied in SOT23 package (JEDEC TO-236AB), 3-terminal plastic case with cathode-indicating marking on top surface. Pin 1 = anode, Pin 2 = cathode (common terminal in dual variants), Pin 3 = not connected (NC) in single-diode configuration.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZMV834ATA and ZC833BTA, ZC834ATC uniquely balances wide capacitance range, 25 V robustness, and hyperabrupt linearity - making it optimal for industrial TCXOs and wide-pull VCXOs where both voltage headroom and tuning resolution are critical.

Availability

ZC834ATC is available at Aetrix Electronics and suitable for VCXO frequency pulling, TCXO temperature compensation networks, wireless transceiver VCO cores, and pager RF front-end filtering requiring stable component supply and consistent hyperabrupt CV performance across production lots.

Supply support for ZC834ATC 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 plc was a UK-based ISO 9001 and TS16949-certified manufacturer specializing in high-performance analog and RF discrete semiconductors before its acquisition by Diodes Incorporated in 2008.

The 830 series varactors were developed to address demand for precision-tuned, low-phase-noise timing components in wireless infrastructure and portable communications equipment - emphasizing controlled CV slope, high Q, and miniature SMT packaging.

FAQ

What is the maximum recommended reverse voltage for continuous operation of ZC834ATC?

The absolute maximum reverse voltage is 25 V, but continuous operation should be limited to ≤20 V to maintain long-term reliability and avoid accelerated junction degradation. Derating to 15 V is advised for high-temperature environments (>85°C) or mission-critical timing applications.

Does ZC834ATC require external biasing circuitry to function in a VCXO?

Yes - ZC834ATC operates only under reverse bias and requires a stable, low-noise DC tuning voltage applied between cathode (Pin 2) and anode (Pin 1). A series resistor (1–10 kΩ) and RF choke or capacitor are typically used to isolate the tuning line from oscillator AC signals while preventing noise coupling.

How does the hyperabrupt junction improve performance versus an abrupt varactor in TCXO designs?

The hyperabrupt junction yields a steeper, more linear C-V slope near zero bias - enabling finer frequency resolution per volt and better matching to crystal tempco curves. This reduces residual uncorrected drift after analog compensation, improving overall TCXO stability to ±0.5 ppm over –40°C to +85°C in optimized implementations.

Is ZC834ATC RoHS compliant and lead-free?

Yes - ZC834ATC complies with the EU RoHS Directive (2011/65/EU) and contains no lead, mercury, cadmium, hexavalent chromium, PBB, or PBDE. The SOT23 package uses matte tin (Sn) lead finish, qualified for standard Pb-free reflow profiles (JEDEC J-STD-020D).