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Digital Logic

Digital logic is a wide-open and rapidly-growing field, and yet every single digital device operates on some combination of three basic logic functions: AND, OR, and NOT. Even the most complex circuit contains some combination of these three functions, and can be reduced to them in the final analysis. These pages define and describe the three basic functions and some of the unending ways in which they can be usefully combined.

Combinational Logic

In many cases, logic gates are combined in various ways and the output signal(s) is/are determined entirely by the current combination of input signals.

Sequential Logic

Sometimes a circuit must remember its current or previous state. In such cases, the output state of a circuit is determined by what has happened an in what order in the past.

Alternate Flip-Flop Circuits

There are many different ways to design flip-flops.

Counters

Flip-flops are much more useful when you combine them and use them in groups. In general, there are two categories of applications that use multiple flip-flops. One of these is the counter.

Registers

In addition to counters, we also have registers, which can hold a multi-bit value while something is done with that value.

The 555 Timer

The 555 timer is a deceptively simple circuit which has proved to be extremely useful in a wide range of applications.