Page 62 - The Art and Science of Analog Circuit Design

Gregory I A. Kovacs

of smoke pre-packaged inside. If, through an inadvertent wiring error,
conditions arise through which the smoke is permitted to escape, the de-
vice ceases to function. We also train the students to recognize and distin-
guish the smells of different burning components ("Ah yes, a carbon
resistor seems to have burned up in this circuit... smells like 220KQ.").
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I am not kidding about this, but not more than A of the EE students at
this level have ever used a soldering iron before! In contrast, nearly all of
them have driven a BMW and can explain leveraged buyouts in great
detail (I presume this is a phenomenon more common at schools where
yuppy pupae are present in large numbers). After a little trial and error,
most of them learn which end of the soldering iron is hot (I am told that
those who never really figure this out generally transfer to a local state-
ran university where they can just write software, but I have no concrete
evidence of this). Pretty soon, they not only know how to solder, but also
how to use a wide range of up-to-date test equipment. (I worry about the
ones who keep looking for an "auto setup" button on a voltmeter, though!
. . more on this below.)
At this point, we get the students into the guts of Boot Camp: design
it, SPICE it, make it work, and examine the differences between the
SPICE model and the real thing. The idea is to teach simulation as "vir-
tual instruments" and then introduce the real ones (the type with knobs).
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We provide SPICE decks for each circuit that are already on the student
computers. We leave out critical component values for the students to
choose. They have to come to lab with a running simulation and then
build the circuit. This can be fun to watch the first time, as the students
look around the lab for 10,000 amp current sources, diodes with forward
voltages of exactly 0,700V, and 13.4567E3 ohm resistors. Eventually,
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they figure things out and get things working.
We ask them to simulate and build a lot of discrete circuits, including
power supplies, basic op amp circuits, single-transistor amplifiers, a sim-
ple op amp built from discretes, and power amplifiers. After that they
build a project of their own choosing, demonstrating their analog design
skills. This exercise gives them a chance to construct a complete circuit
from scratch and write an instruction manual, specification sheet, and
marketing sheet for whatever it is. Some students have built really amaz-
ing things, such as a waveform synthesizer, a heterodyne spectrum ana-
lyzer, an infrared remote control system, an acoustic rangefinder, etc.
Some have built devices that are also humorous, including a fake leopard

"Gee, Dad, why do they call them SPICE decks?"
"Well, son, way back before they found a practical use for the 'Newton' in 2027, computers used
punched paper cards as a way to enter data and programs. We called a stack of those cards a
'deck'."
Our current sources only go to 9,000 amps, we keep the 0.700-V diodes in another room, and
they need to specify resistor values to a few more decimals or our component supplier doesn't
know which value to provide.

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