## Overview of the HIR7373C The **HIR7373C** is a high-intensity Infrared (IR) Emitting Diode manufactured by Everlight Electronics. It is encapsulated in a water-clear plastic package and is designed to emit light in the near-infrared spectrum, making it invisible to the human eye but detectable by silicon photodetectors. --- ### Key Technical Specifications The following table outlines the primary electrical and optical characteristics of the HIR7373C: | Parameter | Symbol | Typical Value | Unit | | :--- | :--- | :--- | :--- | | **Peak Wavelength** | $\lambda p$ | 850 | nm | | **Forward Voltage** | $V_F$ | 1.45 (Max 1.65) | V | | **Continuous Forward Current** | $I_F$ | 100 | mA | | **Radiant Intensity** | $I_e$ | 40 - 100 | mW/sr | | **Viewing Angle** | $2\theta_{1/2}$ | 30 | Degrees | | **Reverse Voltage** | $V_R$ | 5 | V | --- ### Internal Construction and Physics 1. **Material Composition:** The diode is typically fabricated using **GaAlAs** (Gallium Aluminum Arsenide) on a GaAs substrate. This material allows for high efficiency and high output power at the 850nm wavelength. 2. **Package Type:** It features a standard **T-1 3/4 (5mm)** package. The "C" in the part number usually denotes a "Clear" lens, which ensures maximum light transmission without diffusion. 3. **Spectral Bandwidth:** It has a relatively narrow spectral bandwidth ($\Delta\lambda$) of approximately 45nm, ensuring it matches well with 850nm-optimized sensors. --- ### Applications The HIR7373C is commonly integrated into the following systems: * **CCTV & Night Vision:** Used as an illuminator for security cameras. * **Infrared Applied Systems:** Remote controls and high-speed data transmission. * **Optical Switches:** Detecting presence or movement in industrial machinery. * **Biometric Systems:** Used in some types of vein scanning or pulse oximetry designs. --- ### Implementation Example (Basic Circuit) To drive the HIR7373C safely, a current-limiting resistor is required. Below is a conceptual calculation for a 5V supply: ```python # R = (V_supply - V_forward) / I_forward V_supply = 5.0 V_f = 1.45 I_f = 0.05 # Using 50mA for safety (Max is 100mA) resistor_value = (V_supply - V_f) / I_f print(f"Required Resistor: {resistor_value} Ohms") # Result: 71 Ohms (Standard value 75 or 82 Ohms) ```