Flip-flop circuit and scan chain using the same

A flip-flop circuit is provided. The flip-flop circuit receives a test signal at a test-in terminal and a data signal at a data-in terminal and generates a scan-out signal. The flip-flop circuit includes a buffer and a scan flip-flop. The buffer has an input terminal coupled to the test-in terminal and an output terminal and further has a first power terminal and a second power terminal. The buffer operates to generate a buffering signal. The scan flip-flop receives the buffering signal and the data signal. The scan flip-flop is controlled by a test-enable signal to generate the scan-out signal according to the buffering signal or the data signal. The scan flip-flop further generates a test-enable reverse signal which is the reverse of the test-enable signal. The first power terminal of the buffer receives the test-enable signal or the test-enable reverse signal.