Of Reference Designators and Datasheets

Short post about random stuff. This site has been a reference for me many a time during work: http://en.wikipedia.org/wiki/Reference_designator

I'm sure most engineers know at least the common ones by heart. Anyway, these reference designators are how parts are named--usually the letter(s) followed by a number. So they'd be like C412, R78, or Q90. The C's and R's are pretty self-explanatory, but it did take me some time to get used to recognizing transistors as Q's or circuits as U's.

Another thing is pins. Each part has a certain number of pins (which matches the number of pads on the board). One can just think of them as connections. So resistors and capacitors each have two; a signal comes in one end and out the other. A transistor has three, different types of gates have three or more. Why is this important?

Datasheets. When I come across parts that PADS doesn't have built in, I have to make them myself to place on the board. As you would expect, a schematic symbol does not look like the actual part itself; a capacitor is not just two lines in reality, and a resistor is not just a series of spikes. All parts are of a certain type, and they have standardized names, like NC7SZ00.

These names meant nothing to me either when I started out, but apparently every one has its own datasheet, which is easily Google-able. For example: http://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS012156.PDF

On the first page are two diagrams; the one on the left is for schematic purposes, and the one on the right is how it looks like in real life, as well as the shape I make to place in PADS. This particular part has five pins--two inputs, one output, one power, and one ground (I don't know what it means either -__-).

Sadly for me, I didn't know about this stuff until a couple weeks ago, so I had been struggling along before and wondering why the hell did stuff not fit together. Turns out I numbered the pins wrong when making the footprint and stuff like that. Well, luckily I can change parts relatively easily.

On the bright side, I got my real paycheck today, and I found out like more than halfway into my job that I make $12.00 an hour. Berkeley's minimum wage is somewhere between $8 and $9. WIN!