## Overview of the TSOP311 Series The **TSOP311** series is a miniaturized receiver module for infrared (IR) remote control systems. It consists of a PIN diode and a preamplifier assembled on a lead frame, with the epoxy package acting as an IR filter. ### 1. Key Internal Components The module is more than just a sensor; it is an integrated circuit (IC) that processes signals. | Component | Function | | :--- | :--- | | **PIN Photodiode** | Converts infrared light into an electrical current. | | **Preamplifier** | Boosts the weak signal from the photodiode. | | **Automatic Gain Control (AGC)** | Adjusts sensitivity to suppress noise and ambient light. | | **Band Pass Filter** | Filters out signals outside the specific carrier frequency (e.g., 30kHz - 56kHz). | | **Demodulator** | Removes the carrier frequency to output the original data pulses. | --- ### 2. Technical Specifications The TSOP311 series is known for its low power consumption and high immunity against ambient light. * **Operating Voltage:** 2.5 V to 5.5 V. * **Supply Current:** Typ. 0.35 mA (Very low power). * **Carrier Frequencies:** Available in versions for 30, 33, 36, 37, 38, 40, 56 kHz. * **Transmission Distance:** Up to 45 meters. * **Directivity:** Half angle $\phi = \pm 45^\circ$. --- ### 3. Pin Configuration The TSOP311 typically has three pins. Looking at the front of the sensor (the side with the "bump"): | Pin Number | Name | Description | | :---: | :--- | :--- | | 1 | **OUT** | Data Output (Active Low). | | 2 | **GND** | Ground connection. | | 3 | **Vs** | Power Supply (2.5V - 5.5V). | --- ### 4. Basic Application Circuit To ensure stable operation, a simple RC filter is recommended to suppress power supply ripples. ```cpp // Schematic Representation: // [Vs] ----[ 100 Ohm Resistor ]----+---- [Pin 3: Vs] // | // [ 4.7 uF Capacitor ] // | // [GND] ---------------------------+---- [Pin 2: GND] // [Pin 1: OUT] ------------------------> [Microcontroller Input] ``` ### 5. Distinctive Features * **Internal Filter:** It effectively shields against EMI (Electromagnetic Interference). * **TTL/CMOS Compatibility:** The output can be directly connected to a microprocessor. * **Insensitivity to Sunlight:** The black epoxy mold blocks visible light while allowing IR to pass through. ---