Summary
Logic gates are built using MOSFETs. LT-Spice simulations of simple logic gates enable us to see actual voltage waveforms in digital systems.
Importantly, digital systems are not digital but analogue! Digital refers to the design technique. We design digital systems assuming zeros and ones are transmitted between logic gates. This level of abstraction considerably simplifies digital system design.
When it comes to implementation though, it must be appreciated that the waveforms in a digital system are analogue waveforms. Moreover, they are very high frequency waveforms. A 50 MHz clock is not a 50 MHz signal! A square wave has very sharp transitions. A Fourier analysis shows these transitions contain extremely high frequency components. Depending on the desired rise times, a bandwidth of at least ten times the clock frequency is typically required.
Files and Video
The LT-Spice files are in this zip file.
The accompanying video is here.