Digital circuit is to achieve a certain logic function of the circuit, known as the logic circuit, also known as the switch circuit. Transistors in this circuit are generally operating in the switch state. The digital circuit can be composed of discrete components (such as inverter, self-excited multivibrator etc.), but now the vast majority is composed of integrated circuits (such as gate or gate circuit, etc.). To understand the digital circuit, first of all should master some basic knowledge of digital circuit; second is to understand the various logical symbols and output binary logic element input relations; and should also have some knowledge of logic algebra. With these basic knowledge, but also to understand the digital circuit has laid a good foundation.
To understand the composition and structure of logic circuit function by reading circuit instructions, you can also read the truth table, understanding between the output and input of the "yes" or "no" logical relationship, grasp the logic function of each module.
Two, component function to see pin
Digital circuits are often used with a variety of logic functions of the integrated circuit, this will make the whole circuit more simple and reliable. But it also brings some difficulties to the knowledge map. Because do not see the internal components of the integrated circuit and circuit, can see many external pins, the pins of each role, these pins with other external components or circuit connection, to achieve a certain function. In fact, a lot of time does not need to know the internal circuit of the integrated circuit components, only to understand the function of each pin can be. The function of each pin of the integrated circuit is indicated in the text, such as the circuit does not give the text description or parameters, then the relevant manual should be consulted to understand the logic function of the integrated block and the function of each pin. Some of the commonly used integrated circuit operational amplifier, such as LM324, four 74LS00, 2 INPUT NAND gate 555 timing circuit, the reader should remember the pin function, the fast and accurate map help.
Three, functional decomposition to see the module
The digital circuit according to the signal flow of the system is divided into several functional modules, each module is relatively independent of the function of module interaction analysis, when necessary, can list the input and output of each module logic truth table.
Four, comprehensive look at the whole
To connect each module, the analysis of the circuit from the input to the output of the complete work process, when necessary, can be drawn about the work of the waveform diagram, in order to help the analysis of the logic function of the circuit, understanding.