Integrated circuit with logic function in digital circuit

Integrated circuits with various logic functions are often used in digital circuits, which makes the entire circuit simpler and more reliable. But it also brings some difficulties for understanding. Because you can't see the internal components and circuit components of the integrated circuit, you can only see many external pins. These pins have their own functions. These pins are connected with other external components or circuits to achieve certain functions. . In fact, many times you do not need to know the internal circuit composition of the integrated circuit, just need to know the function of the external pins. The functions of each pin of the integrated circuit are marked with text. If no text description or parameter is given in the circuit, the relevant manual should be consulted to understand the logic function of the integrated block and the function of each pin. For some commonly used integrated circuits, such as the commonly used operational amplifier LM324, four 2-input NAND gates 74LS00, 555 time base circuit, etc., the reader should remember the function of each pin, which is helpful for fast and accurate mapping.