The circuits of the first three lessons in this course are humbler than what you will see later, and the devices you meet here are probably more familiar to you than, say, transistors, operational amplifiers – or microprocessors: Ohm’s Law will surprise none of you; 
probably sounds at least vaguely familiar.
But the circuit elements that this section treats – passive devices – appear over and over in later active circuits. So, if a student happens to tell us, “I’m going to be away on the day you’re doing Lab 2,” we tell her she will have to make up the lab somehow. We tell her that the second lab, on RC circuits, is the most important in the course. If you do not use that lab to cement your understanding of RC circuits – especially filters – then you will be haunted by muddled thinking for at least the remainder of the analog part of the course.
Resistors will give you no trouble; diodes will seem simple enough, at least in the view that we settle for: they are one-way conductors. Capacitors and inductors behave more strangely. We will see very few circuits that use inductors, but a great many that use capacitors. You are likely to need a good deal of practice before you get comfortable with the central facts of capacitors’ behavior – easy to state, hard to get an intuitive grip on: they pass AC, block DC, and only rarely cause large phase shifts.
We should also restate a word of reassurance: you can manage this course perfectly even if the “
” in the expression for the capacitor’s impedance is completely unfamiliar to you (it’s the square root of minus 1). If you consult AoE, and after reading about complex impedances in AoE’s spectacularly dense Math Review (Appendix A) you feel that you must be spectacularly dense, don’t worry. That is the place in the course where the squeamish may begin to wonder if they ought to retreat to some slower-paced treatment of the subject. Do not give up at this point; hang on until you have seen transistors, at least. One of the most striking qualities of this book is its cheerful evasion of complexity whenever a simpler account can carry you to a good design. The treatment of transistors offers a good example, and you ought to stay with the course long enough to see that: the transistor chapter is difficult, but wonderfully simpler than most other treatments of the subject. You will begin designing useful transistor circuits on your first day with the subject.
It is also in the first three labs that you will get used to the lab instruments – and especially to the most important of these, the oscilloscope. It is a complex machine; only practice will teach you to use it well. Do not make the common mistake of thinking that the person next to you who is turning knobs so confidently, flipping switches and adjusting trigger level – all on the first or second day of the course – is smarter than you are. No, that person has done it before. In two weeks, you too will be making the scope do your bidding – assuming that you don’t leave the work to that person next to you, who knew it all from the start.
The images on the scope screen make silent and invisible events visible, though strangely abstracted as well; these scope traces will become your mental images of what happens in your circuits. The scope will serve as a time microscope that will let you see events that last a handful of nanoseconds: the length of time light takes to get from you to the person sitting a little way down the lab bench. You may even find yourself reacting emotionally to shapes on the screen, feeling good when you see a smooth, handsome sinewave, disturbed when you see the peaks of the sine clipped, or its shape warped; annoyed when fuzz grows on your waveforms.
Anticipating some of these experiences, and to get you in the mood to enjoy the coming weeks in which small events will paint their self-portraits on your screen, we offer you a view of some scope traces that never quite occurred, and that nevertheless seem just about right: just what a scope would show if it could. This drawing was posted on my door for years, and students who happened by would pause, peer, hesitate – evidently working a bit to put a mental frame around these not-quite-possible pictures. Sometimes a person would ask if these are scope traces. They are not, of course; the leap beyond what a scope can show was down to the artist: Saul Steinberg. Graciously, he has allowed us to show his drawing here. We hope you enjoy it. Perhaps it will help you to look on your less exotic scope displays with a little of the respect and wonder with which we have to look on the traces below.
