Basically anything that has to do with processing an analog signal. It's always faster to do that with analog electronics rather than using a ADC, doing the com

Basically anything that has to do with processing an analog signal. It's always faster to do that with analog electronics rather than using a ADC, doing the computation in the digital domain, and then getting the result back to the analog world with an ADC. One example, if I need something that when two switches are triggered will turn on a light bulb (basically an AND gate) it's obviously faster doing that with an analog (mechanical) device, that is the two switches wired in series, than acquiring the signal with a microcontroller and outputting a signal to turn on the light bulb. Thinking about the industrial world, there are cases where you have constraints about speed and real time that make sense to do signal processing with analog components rather than digital ones. And that was always the case before computers where invented, by the way (missile guidance systems were purely analog, as one example, you can do a lot of stuff!)