D-type flip-flop
Sequential circuit capturing data input D on clock edge and holding until next edge. D-type flip-flops are memory elements for state machines and registers.
Formula
Q = D (on clock edge)
Real World
Each bit in your laptop's RAM refresh circuit uses D-type flip-flops to hold data values stable between clock cycles, which is how your unsaved document stays in memory while you type.
Exam Focus
State that output Q only changes on the clock edge, not between edges — vague timing descriptions lose marks.
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