17.7 Consider an inverter for which tPLH, tPHL, tTLH, and tTHL are 200 ps, 150 ps, 250 ps, and 100 ps, respectively. The rising and falling edges of the inverter output can be approximated by linear ramps. Also, for simplicity, we define tTLH to be 0% to 100% (rather than 10% to 90%) rise time, and similarly for tTHL. Two such inverters are connected in tandem and driven by an ideal input having zero rise and fall times. Calculate the time taken for the output voltage to complete its excursion for (a) a rising input and (b) a falling input. What is the propagation delay for the inverter?
(a) 475 ps (b) 400 ps; tp = 175 ps