Pulse shaper

The diagram shows how the four gates contained in a 4077 may be used to build a circuit that doubles the frequency of a signal applied to it. In other words, it generates a pulse for every edge of the input signal: the pulse width is determined by the internal delay of gates IC(1a)-IC(1c). To that end, the original signal at pin 13 is compared with the delayed signal at pin 12. Because of the XNOR function of IC(1d), any level difference between the two is translated into a level change at the output of IC(1d).