Basic Gates

    The following truth table details the function of commonly used gates. Each entry in the table list the input logic levels and the output for that input combination. This table lists gates (aside from an inverter) with two inputs.

    Gates with more than two inputs are available for all of the types shown with the exception of the inverter. In gates with more than two inputs, the same functionality is extended to the additional inputs. For instance, a four input AND gate’s output will be high when all four inputs are high and a four input OR gate’s output will be high when one or more of its inputs are high. An XOR (or exclusive OR) gate might be confusing to some when it has more than two inputs. An XOR gate’s output is only high when one of its inputs is high. When two or more inputs are high, the output is low.

    Some gates are available with one or more inverted inputs. Logically, this is the equivalent of adding an inverter to the inverted input as shown in the following figure.

copyright © 2021 John Miskimins