
CHAPTER 9
Propagation Delay and Timing
Defects in Combinational Logic
9.1 INTRODUCTION
To this point in the text, combinational logic circuits have been treated as though they
were composed of “ideal” gates in the sense of having no propagation delay. Now it is
necessary to take a step into the real world and consider that each gate has associated
with it a propagation time delay and that, as a result of this delay, undesirable effects may
occur.
Under certain conditions unwanted transients can occur in otherwise steady-state signals.
These transients have become known as glitches, a term that derives from the German
glitsche, meaning a “slip” (hence, ...