同步电路是一种由定时器信号子电路所同步的一种时序逻辑电路。 在一个同步电路中，他的组件中逻辑等级的每一个改变都是同时的。所有的转变都是遵循一个特别的同步信号，称为"时钟"（时脉）。不管逻辑的炼结有多长，在于时钟（时脉）以及其他部份的逻辑转变都是没有延迟的。所以在整个电路的行为-在任意一点-可以在任何的速度精确的被预见。在实际的电路中，时钟源到达各个寄存器的线网长度不同，因此需要使用一些时钟缓冲器来尽量降低时钟偏移的影响。

A synchronous circuit is a digital circuit in which the changes in the state of memory elements are synchronized by a clock signal. In a sequential digital logic circuit, data is stored in memory devices called flip-flops or latches. The output of a flip-flop is constant until a pulse is applied to its "clock" input, upon which the input of the flip-flop is latched into its output. In a synchronous logic circuit, an electronic oscillator called the clock generates a string of pulses, the "clock signal". This clock signal is applied to every storage element, so in an ideal synchronous circuit, every change in the logical levels of its storage components is simultaneous. Ideally, the input to each storage element has reached its final value before the next clock occurs, so the behaviour of the whole circuit can be predicted exactly. Practically, some delay is required for each logical operation, resulting in a maximum speed at which each synchronous system can run.