The **5HF1.25-R** is a specific model of a subminiature, fast-acting ceramic tube fuse. It is commonly used in industrial and consumer electronics to protect sensitive components from overcurrent conditions. --- ### 1. Key Technical Specifications The part number follows the Bel Fuse naming convention. Below are the primary technical parameters: | Feature | Specification | | :--- | :--- | | **Current Rating** | 1.25 Amperes | | **Voltage Rating (AC)** | 250 Volts | | **Fuse Characteristic** | Fast-Acting (Quick Acting) | | **Body Material** | Ceramic | | **Mounting Type** | Through-Hole (Radial Leaded) | | **Interrupting Rating** | 1500A @ 250V AC | | **RoHS Compliant** | Yes (indicated by the "-R" suffix) | --- ### 2. Physical Dimensions and Design The "5HF" series is known for its compact, vertical form factor. * **Form Factor:** 5x20mm equivalent performance, but often configured with radial leads for direct PCB mounting. * **Construction:** The ceramic body provides high breaking capacity (interrupting rating), meaning it can safely extinguish an arc even during a significant short circuit. * **Termination:** Pigtail/Radial leads allow the fuse to be soldered directly to the board, eliminating the need for a separate fuse clip or holder. --- ### 3. Electronic Behavior * **Fast-Acting:** Unlike "Slow-Blow" fuses, the 5HF1.25-R is designed to open almost instantly when the current exceeds 1.25A significantly. This protects delicate semiconductors (like ICs or transistors) that cannot withstand even brief surges. * **Low Resistance:** It features low internal resistance to minimize voltage drop across the component during normal operation. * **Operating Temperature:** Generally rated to function between -55°C to +125°C, making it suitable for harsh environments. --- ### 4. Common Applications * **Power Supplies:** Primary protection on the AC input side. * **LED Lighting:** Protecting driver circuits. * **Battery Chargers:** Preventing overcurrent during charging cycles. * **Consumer Electronics:** Used in monitors, printers, and set-top boxes where space is limited.