Troubleshooting Analog Circuits (1991) [pdf]

This is still an essential guidebook in so many ways.

Here's one:

>Many classes of circuits are neither entirely analog nor entirely digital.

>when problems develop in circuits containing both analog and digital elements, finding a solution is more likely to require that you summon your analog expertise than your digital knowledge.

>Digital ICs have more than a few analog subtleties. And even multiplexers, which you may have thought of as purely analog, have some quirks that result from their close association with the digital world.