The term **"105-R"** in the electronics industry typically refers to one of two things: a specific electrical rating for components (temperature and resistance) or a specific series of surface-mount (SMD) power inductors. --- ### 1. 105-R as a Power Inductor (SMD) The most common hardware component labeled "105" or "105R" is a **Shielded/Unshielded SMD Power Inductor**. These are widely used in DC-DC converters and power supplies. | Feature | Specification | | :--- | :--- | | **Inductance Value** | The "105" code typically translates to **1,000 $\mu$H** (10 followed by five zeros in picohenries, or more commonly 10 followed by 5 as a multiplier). | | **Physical Size** | Usually approximately 10mm x 10mm x 5mm. | | **Core Material** | Ferrite. | | **Applications** | Laptops, LED drivers, switching regulators, and power supplies. | --- ### 2. The "105" Temperature Rating In the context of **Electrolytic Capacitors**, "105" is a critical thermal specification rather than a part number. * **105°C Rating:** This indicates the maximum operating temperature the component can withstand while maintaining its rated lifespan. * **Comparison:** Standard capacitors are often rated at 85°C. A 105°C rated part is considered "High Temp" and is used in environments with poor airflow or high heat (like inside an ATX power supply). * **The "R" Suffix:** In capacitor series, "R" often denotes **Low ESR** (Equivalent Series Resistance) or **RoHS Compliant** (lead-free). --- ### 3. Resistor Marking (105R) If the code is printed on a precision resistor, it follows the standard numerical marking system: * **105:** The first two digits (10) are the significant figures, and the third (5) is the multiplier ($10^5$). * $10 \times 100,000 = 1,000,000$ Ohms (**1 MΩ**). * **105R:** If the 'R' acts as a decimal point (standard in some marking systems), it could mean **105 Ohms**. --- ### Summary Table: Which 105-R do you have? | Component Type | Meaning of "105-R" | Identification Tip | | :--- | :--- | :--- | | **Inductor** | 1.0mH Inductance | Square/Drum shape, usually grey or black. | | **Capacitor** | 105°C Heat Resistance | Cylindrical, usually has "105°C" printed on the sleeve. | | **Resistor** | 1 Megaohm or 105 Ohm | Small flat chip (SMD) or color-coded cylinder. | ---