I studied Electrical Engineering in college.
One of the basic electrical components one must learn is called an operation amplifier. Op-amps have a ton of practical circuitry uses in our world such as inverters, phase-shifters, amplifiers, converters, and switches.
To perform circuit analysis and design with op-amps, you can assume that the op-amp is “ideal” — this means you assume several characteristics to be categorically perfect.
Ideal op-amps use no power, have infinite input impedance, unlimited gain-bandwidth and slew rate, no input bias current, and no input offset. They have unlimited voltage compliance.
With these assumptions, you go on your merry way designing or analyzing what’s happening — on paper.
And then you get in the lab. Only practical op-amps exist in the real world, and hence, in the lab.
Practical op-amps consume power, have high, but not infinite, impedance, have limited gain-bandwidth and limited slew rate, have some input bias current and input offset voltage. Voltage compliance is limited by the power supply rail, or frequently even less.
Ideal versus the real world.
Ideal can be assumed for analysis purposes — thought experiments, hypotheses, philosophical systems, “should” statements.
But never forget that, as humans, we live in the real world.
