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Circuit Description

This circuit shows the basic archictecture of the so-called JK-flipflop, which consists of a few logic gates in front of a D-flipflop. On the rising edge of the clock, the flipflop enters a new state depending on the input values on the J and K inputs:

• J=0, K=0: store (Q=Q)
• J=0, K=1: clear (Q=0)
• J=1, K=0: set (Q=1)
• J=1, K=1: toggle (Q=!Q)

While JK-flipflops are not often used in modern integrated circuits, they were very popular during the TTL era of circuit design because of their flexibility. A JK flipflop can emulate most other types of flipflops including D-flipflops and T-flipflops with suitable wiring of the J and K inputs (a few additional gates in front of the J and K inputs might be required). To ease the construction of counters, JK-flipflops are often sensitive to the falling-edge of the clock signal.

The actual implementation of a JK-flipflop in TTL-technology does not rely on the circuit shown here, but uses a master-slave flipflop structure demonstrated in the next applet.