Logic element or logic circuit is an element (circuit) with logic function, also known as gate circuit. Common ones are "and" door, "or" door, "not" door, "and not" door and "or not" door. These gates can be used to form various logic functional circuits required by electronic computers. Different logic elements have different design characteristics. These characteristics vary with CMOS, TTL and ECL. These features include input power consumption, speed / energy relationship, packaging form, edge change rate and voltage drift value. Some logic elements have a clock offset circuit that controls the internal edge change of the internal logic gate in order to maintain accurate transmission delay. A feasible way to reduce EMI and improve signal quality is to choose the logic element with the slowest speed as far as possible, while maintaining an appropriate timing tolerance, and try to use the element with a rise time of more than 5 ns. In general, do not use components that are faster than the actual needs or timing requirements of the circuit.