## Overview of the MC74ACT05 The **MC74ACT05** is a high-performance, low-power integrated circuit (IC) belonging to the ON Semiconductor (formerly Motorola) ACT family. It consists of **six independent inverters with open-drain outputs**. This specific device is designed using silicon-gate CMOS technology and is compatible with TTL (Transistor-Transistor Logic) input levels, making it ideal for interfacing between different voltage logic families. --- ### Key Technical Specifications | Parameter | Specification | |:---|:---| | **Logic Type** | Inverter (Hex) | | **Output Type** | Open-Drain | | **Supply Voltage ($V_{CC}$)** | 4.5V to 5.5V | | **Input Threshold** | TTL Compatible | | **Output Current ($I_{OL}$)** | 24 mA | | **Propagation Delay** | ~6.5 ns (Typical) | | **Operating Temperature** | -40°C to +85°C | --- ### Functional Breakdown #### 1. Hex Inverter Logic The "Hex" prefix indicates there are six individual circuits inside one chip. Each circuit performs the **NOT** logic function ($Y = \bar{A}$). If the input is HIGH, the output transistor turns on; if the input is LOW, the output transistor turns off. #### 2. Open-Drain Output Unlike standard push-pull outputs, an open-drain output lacks the upper (P-channel) transistor. * **LOW State:** The output is actively pulled to Ground (GND). * **HIGH State:** The output enters a high-impedance state (floating). * **Requirement:** An external **pull-up resistor** is necessary to define the HIGH logic level. #### 3. ACT Technology The "ACT" designation stands for **Advanced CMOS with TTL-compatible inputs**. This means the chip consumes very little static power (typical of CMOS) but can be driven by older TTL logic parts without needing level shifters. --- ### Pinout Configuration (14-Pin) | Pin Number | Function | Description | |:---:|:---:|:---| | 1, 3, 5, 9, 11, 13 | $A_n$ | Data Inputs (1-6) | | 2, 4, 6, 8, 10, 12 | $\bar{O}_n$ | Open-Drain Outputs (1-6) | | 7 | GND | Ground | | 14 | $V_{CC}$ | Positive Supply Voltage | --- ### Common Applications 1. **Wired-AND Logic:** Multiple open-drain outputs can be connected to a single pull-up resistor. If any inverter output goes LOW, the entire line goes LOW. 2. **Level Shifting:** By connecting the pull-up resistor to a different voltage rail (e.g., 3.3V or 12V), the MC74ACT05 can interface 5V logic with other voltage levels. 3. **Driving Heavy Loads:** The 24mA sink capability allows it to drive LEDs or small relays directly. --- ### Internal Logic Diagram ```text Vcc (14) | +----+----+ | [INV] |--- Output (2) | Input (1) | | | [INV] |--- Output (4) | Input (3) +----+----+ GND (7) ``` *(Simplified view of 2 out of 6 gates)*