EXOR edge detector

38 This very simple edge detector can find its way into many applications. It relies on the propagation delay of the EXOR gates to provide an output pulse for every incoming edge, both positive and negative going. The incoming waveform is fed directly to one input of N4, the last of the four gates in the circuit diagram. This input signal is also fed through the other three gates N1 ... N3 in series and this "processed" signal becomes the other input to N4. In the case of the 7486 quad EXOR gate, the propagation delay (that is the time it takes for a signal to travel "through" the gate) is in the order of 15 ns. It therefore follows that the "processed" signal will be delayed by 3x 15 ns = 45 ns. Since the output of an EXOR gate is low when both inputs are equal, N4 will give a negative pulse out for the duration of the propagation delay time of gates N1 ... N3. It will be obvious that this circuit will also be quite useful as a frequency doubler.H EXOR edge detector N1 ... N4 = 7...