Decoupling power rails

Adequate decoupling of power rails of most circuits is a seriously underestimated necessity. Particularly in the design of printed-circuit boards, it often happens that at the last moment the thought occurs that there is no or insufficient space left for decoupling capacitors, srnall though these normally are. His, of course, not surprising that such negligence often results in spontaneous oscillation in analogue circuits and unreliable operation of digital circuits. Especially sequential digital circuits, such as dividers, counters and bistables are prone to these problems, the causes of which are normally very difficult to find.