The **FST20180** is a high-power **Schottky Barrier Rectifier** diode. It is typically designed in a "Common Cathode" configuration and is housed in a heavy-duty power package (usually TO-249 or similar modules). --- ## 1. Core Technical Specifications The part number "FST20180" provides a shorthand for its primary electrical capabilities. | Parameter | Value | Description | | :--- | :--- | :--- | | **Max Average Rectified Current ($I_{O}$)** | 200 Amps | The total current capacity (100A per leg). | | **Peak Repetitive Reverse Voltage ($V_{RRM}$)** | 180 Volts | The maximum voltage it can block in reverse. | | **Forward Voltage Drop ($V_{F}$)** | ~0.85V to 0.95V | The voltage lost when current flows through the diode. | | **Operating Temperature Range** | -55 to +175 °C | The thermal limits for the silicon junction. | --- ## 2. Key Internal Components & Features ### A. Schottky Barrier Technology Unlike standard silicon diodes that use a P-N junction, the FST20180 uses a **metal-to-silicon junction**. * **Benefit:** This results in much faster switching speeds and a lower forward voltage drop compared to standard recovery diodes. * **Trade-off:** Higher reverse leakage current, especially at high temperatures. ### B. Common Cathode Configuration The device usually contains two diode chips inside a single module. * **Terminal 1 (Anode 1):** Input for the first phase. * **Terminal 2 (Anode 2):** Input for the second phase. * **Terminal 3 (Common Cathode):** The combined output (usually connected to the metal base or a center stud). ### C. Construction & Packaging * **Guard Ring Protection:** The internal silicon dies include a guard ring for "dv/dt" protection, which helps prevent failure during high-voltage transients. * **Hermetic/Semi-Hermetic Seal:** Designed for industrial environments to prevent moisture ingress. * **Baseplate:** Typically nickel-plated copper for maximum heat dissipation to a heatsink. --- ## 3. Applications Due to its high amperage and fast switching, the FST20180 is used in: 1. **Switch Mode Power Supplies (SMPS):** Providing rectification for high-frequency outputs. 2. **Free-Wheeling Diode:** Used in motor control circuits to protect against inductive spikes. 3. **Battery Chargers:** Handling high current flow for industrial battery banks. 4. **Solar Inverters:** Used in the DC-to-DC conversion stages. --- ## 4. Typical Symbol Diagram ```text Anode 1 (1) ----|>|----| |---- Cathode (Center/Base) Anode 2 (2) ----|>|----| ``` ---