The **BP104FAS** is a high-speed silicon PIN photodiode specifically designed for detecting infrared (IR) light. It is commonly used in remote control circuits, light barriers, and optical communication. --- ### 1. Key Technical Specifications The following table outlines the core electronic characteristics of the BP104FAS: | Parameter | Specification | Description | | :--- | :--- | :--- | | **Spectral Sensitivity** | 820 nm to 1100 nm | Peak sensitivity is around 950 nm (Infrared). | | **Package Type** | SMT (Surface Mount) | Standard SMT package with a daylight filter. | | **Half Angle** | ± 65° | Wide viewing angle for signal reception. | | **Rise/Fall Time** | 20 ns | High-speed response suitable for data transmission. | | **Reverse Voltage** | 20 V (Max) | Maximum voltage it can withstand in reverse bias. | | **Dark Current** | 2 nA (Typ) | Current flowing when no light is present. | --- ### 2. Physical Design and Features * **Integrated Daylight Filter:** The "F" in the part number often denotes a black epoxy coating that acts as a daylight filter. This blocks visible light and allows only infrared light to pass through, reducing noise from ambient lighting. * **PIN Construction:** Unlike standard photodiodes, the PIN structure (P-type, Intrinsic, N-type) features a wide undoped intrinsic layer. This reduces capacitance, allowing the diode to switch on and off much faster. * **Surface Mount Technology (SMT):** Designed for automated PCB assembly, making it ideal for compact consumer electronics. --- ### 3. Electronic Application Circuit To use the BP104FAS, it is typically connected in **Photoconductive Mode** (reverse biased). This provides the fastest response time. ```python # Simple representation of a Photodiode Receiver Circuit # [VCC] --- [Resistor] --- [Cathode (BP104FAS) Anode] --- [GND] # | # [Signal Out to MCU/Op-Amp] ``` ### 4. Common Use Cases 1. **IR Remote Controls:** Receiving signals for TVs, Air Conditioners, and Hi-Fi systems. 2. **Industrial Sensors:** Detecting objects on conveyor belts or counting pulses in optical encoders. 3. **Data Transmission:** Short-range wireless IR communication links. ---