The **74HC7266** is a high-speed CMOS device containing four independent **2-input Exclusive-NOR (XNOR) gates**. It is commonly used in digital logic circuits for equality checking and phase detection. --- ### 1. Key Technical Specifications The "HC" in the name stands for **High-speed CMOS**, meaning it combines the low power consumption of the CMOS 4000 series with speeds comparable to the Schottky TTL (74LS) series. | Parameter | Specification | | :--- | :--- | | **Logic Type** | XNOR (Exclusive-NOR) | | **Supply Voltage (Vcc)** | 2.0V to 6.0V | | **Input Logic Level (High)** | 3.15V (at Vcc=4.5V) | | **Input Logic Level (Low)** | 1.35V (at Vcc=4.5V) | | **Propagation Delay** | ~10-15 ns (at 5V) | | **Output Current** | ±5.2 mA | | **Operating Temperature** | -40°C to +125°C | --- ### 2. Logic Function & Truth Table The XNOR gate is often called an **"Equality Gate."** The output is **HIGH (1)** only if both inputs are the same (both 0 or both 1). If the inputs are different, the output is **LOW (0)**. **Logic Equation:** $Y = \overline{A \oplus B}$ or $Y = AB + \overline{A}\overline{B}$ #### Truth Table | Input A | Input B | Output Y | | :---: | :---: | :---: | | L | L | **H** | | L | H | **L** | | H | L | **L** | | H | H | **H** | --- ### 3. Pinout Configuration The 74HC7266 is typically housed in a 14-pin DIP or SOIC package. | Pin Number | Symbol | Description | | :--- | :--- | :--- | | 1, 2 | 1A, 1B | Data Inputs (Gate 1) | | 3 | 1Y | Data Output (Gate 1) | | 4, 5 | 2A, 2B | Data Inputs (Gate 2) | | 6 | 2Y | Data Output (Gate 2) | | 7 | GND | Ground (0V) | | 8, 9 | 3A, 3B | Data Inputs (Gate 3) | | 10 | 3Y | Data Output (Gate 3) | | 11, 12 | 4A, 4B | Data Inputs (Gate 4) | | 13 | 4Y | Data Output (Gate 4) | | 14 | Vcc | Supply Voltage | --- ### 4. Common Applications * **Digital Equality Comparators:** Checking if two binary numbers are identical bit-by-bit. * **Parity Generators/Checkers:** Used in error detection systems. * **Phase Detectors:** Comparing the phase of two clock signals. * **Data Encryption/Decryption:** Basic hardware-level logic operations. --- ### 5. Schematic Symbol Example ```text Inputs Output A ----| \ | )O----- Y B ----| / ``` ---