A Story of Electronics: A gut feel approach

ISBN-13: 9781484897416 / Angielski / Miękka / 2013 / 258 str.

Robin Pain

Opis

Hi, this book begins in 1963 with me as a child of 9 trying to understand why my crystal set worked OK with the GPO headphones but not with my home-made earpiece (or with a loudspeaker) - output impedance - that's why But it was not until I was 13 or 14 that I realised this because I did not believe in "output impedance" - how can something such as a battery have output resistance? It is supposed to be supplying current, not hindering it This mystery and others are carefully explained in simple language because this is the book that I would have craved when I was a kid, but I was not good at reading and did not understand any algebra at all. We explain the mystery of the potential divider too (why not just use rheostats, like my Scalextric hand controllers?) and show that everything is just a potential divider - even the Scalextric hand controllers. This is the start of understanding Ohm's Law - input and output impedances and the potential divider, without using any maths, the gut feel. Time passes and we get to 11 years old and we have the chapter on algebra, just enough to understand V / I == R (we have already learned this by rote earlier) but now we use it, but with the geeky equals sign and in a programming manner because ..".we are roughly headed in that direction." And although this book ends in about 1980 we jump ahead here and write some ARM assembler to make the Raspberry Pi act as a "spark gap transmitter" using a piece of wire - this is really grown up stuff for kids. The climax is chapter 8 "TV and Radio Repairman" where I tell the story of how I learned the "secret" of fault finding at age 23 (its Ohm's Law and input and output impedance) and also chapter 9 "The Mighty Click" where we explain "Fourier" without using any maths at all, just picutures of sinusoids and "common sense" and this ties in with the spark gap transmitter and one particular fault finding trick (impulse response) and also the "Dick Parmee" audio test: a square wave. Now we are ready to start designing "by hacking" i.e. by fault finding as we go in chapter 10 Amplifier. I show each step (input and output impedance) and each mistake I make and a photograph of the rat's nest circuit so that you can build it without using the schematic if you prefer. The final amplifier uses bootstrap to get extra gain and we take advantage of the clipping to use this as our guitar amplifier (it is the one shown on the cover of the book). The bootstraping ties in with a description of the gyrator (as described to me by Dick Parmee) and finally ties in with the Sallen-key filters in chapter 17. But before we do Filters, we learn about Negative feedback and common mode and current source so that we can design the classic amplier of chapter 16 and here the output impedance goes down to nearly zero, as we predicted because of the negative feedback. In other words, this book is about input and output impendance (Ohm's Law) with a touch of Fourier Analysis and for the last chapter, a Hint of DSP. But most of all, it is a Story.

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