I already read Jan's answers, I'll make note of when that's
noteworthy.
Max Hauser said:
1. Assuming that you are acquainted with the "cascode" configuration, do
you know where the term came from?
I have no idea (should I add an x-no-archive header?), but my
SWAG/folk etymology answer is that it's a combination of the words
"cascade" where the output of one amplifier stage goes to the input of
the next, NOT where there are multiply quoted lines in long Usenet
threads
, and "cathode" which is the element (in a tube circuit)
used as the signal input in "grounded grid" amplifier configuration.
As with many of these things, the name was surely carried over to
transistor circuits.
[Note! My 1988 answers had this wrong, reflecting a popular myth of which I
was later disabused, but a myth that also made it into the current revision
of a venerable analog-IC text, despite my efforts by sending the accurate
reference to those revising the text, upon their request to me at the time
for historical information. Enough About That.]
2. What is a reflex amplifier?
I remember reading about this 30-odd years ago (it was only of
historic interest even then), had forgotten what it was, then Jan's
answer reminded me.
3. What is the basic principle of a superhet receiver?
As Jan said, but specifically: a local oscillator and mixer stage
that generates an IF frequency that's above human hearing (as
constrasted to a hetrodyne receiver). Or did I just describe the
origins of the name?
Of a regenerative
receiver?
One where the RF input stage (generally the only stage) uses a
variable amount of feedback, controllable by the user on the front
panel, set to just below oscillation at the reception frequency. This
is a high Q active filter, and it has a large amount of amplification
of the signal with just one stage. It can directly drive headphones.
Difference between a mixer and a converter (in RF)?
No wait, it's coming back to me (I never got a ham license but I've
read the ARRL books and stuff, and been to many hamfests)...a mixer is
internal and gives the IF frequency (with a variable LO).
A converter is an external box containing both a fixed LO and a
mixer stage that converts from one RF band (that a receiver does not
receive) to another RF band (that a receiver DOES receive), and which
sits between the antenna and receiver.
4. Who developed the op amp, and when?
[2004 Note: Question 4 preceded George Rostky's excellent recent historical
articles in the trade press, which I recommend, and which themselves have
now achieved misquotation elsewhere. That and plagiarism may be today's
"sincerest form of flattery."]
I recall reading some of Rotsky's writings but not that. Most of
what I know about early op-amps is what Pease has written.
I want to say Philbrick (Pease wrote about working for him) but I
think he was the first to make an op-amp as a solid-state (transistors
instead of tubes) device circa 1960, and not the first op-amp. They
were implemented using vacuum tubes for years before then, perhaps
back to WWII, and used for calculating ballistics.
5. What is the "purple plague?"
6. What is a class-C amplifier and where is it typically used?
Active/amplifying device conducts for less than 180 degrees of the
cycle, used in RF amplifiers, especially high-power (anything over
100mW or so) amplifiers in radio transmitters.
7. Can you describe a tunnel diode?
It has negative resistance over a section of its characteristic
curve (is this forward, or reverse? I forget, or never learned) of I
vs. V. There's a section of the curve where the current goes DOWN as
the voltage goes up. It works (oscillates) up to the microwave range,
and was popular for that band many decades ago, because it was the
only solid-state device that did anything at such a high frequency.
A unijunction transistor?
I recall that it was used in relaxation-type oscillators.
Silicon Controlled Switch, and there must be a difference between
that and an SCR, but I don't know what it is.
(What is the basic principle of each and what are they used for?)
I already told you all I know about them.
8. Traditional op-amp ICs were made whenever possible to run on +- 15
volts. Why that voltage?
Hmm... you could power each rail with ten common "carbon-zinc" 1.5V
flashlight cells in series...
9. What do the following acronyms stand for: PDP,
Programmed Data Processor. The story behind the name is told in a
Creative Computing magazine circa 1977.
Didn't know that was an acronym. I know the plural is Vaxen.
American Standard Code for Information Interchange. (it describes a
7-bit code).
Extended Binary-Coded Decimal Information(?) Code(?). ISTR (perhaps
wrongly) that Hollerith punched-cards used this code.
Never heard of it...
Beat Frequency Oscillator. It oscillates in the IF frequency range,
and is adjustable over that range, injected between IF stage and the
(AM) detector, and converts CW signals into audible tones.
Continuous Wave. Used to describe unmodulated carrier or
transmission of Morse Code or International Morse Code or whatever
it's called.
VSB, VOR, Conelrad?
dunno...
10. What was revolutionary about the 741 op amp?
That it worked.
Jan said that it had internal compensation. I was thinking that it
was unity-gain stable without external compensation (not quite the
same thing), but also, it didn't have the latchup problems that the
earlier 709 had. In other words, it worked.
11. Can you specifically describe the US semiconductor products known by
the following terms: 1N34,
Germanium signal diode, good as RF detector.
The first commercial transistor (or one of the first), but only
because I've read about it here in recent years when its
characteristics and availablility, originally ('50's magazine ads) and
recently (on ebay), was discussed.
2N107, 2N998, 2N1304, 2N2222, 2N3055,
2N2222 was/is the ubiquitous NPN signal transistor, and 2N3055 was
the ubiquitous NPN power transistor. I'm sure there's much more to the
story.
U222, uL900, uL958, uA703, uA709, SN7300 series, SUHL, CCSL, HTL, ECCSL,
Utilogic, COSMOS,
COmplementary Symmetry Metal Oxide Semiconductor. Now just called
CMOS.
Intel 1101, Intel 1702.
12. Identify the following trademarks: Nixie, Pixie, Numitron?
They're apparently all trademarks for numeric indicator tubes that
use a separate element for each number, where a high [compared to
nowadays] voltage activates the neon gas around the element, thus a
number is displayed. Nixie is obviously the one that stuck and became
generic (are any of these trademarks still in force? When did such
tubes cease production? They're NOT still made, are they....).
Some sort of microwave tube...
This is an indicator tube that was commonly used as a tuning
indicator in radios. It has a fouorescent screen and 'shadow' area
that varies in size with an applied voltage.
Jan missed this one. This was the last line of standard "receiving
tubes" developed and manufactured. They were about the same height as
the "miniature" tubes used in "All-American Five" five-tube AM
tabletop radios, but Compactrons were larger in diameter, had 12 or 15
or so (I forget) pins, and had several active elements in each tube,
such as "triple triode." These were the last-ditch effort to extend
the market lifetime for tubes in the 60's when transistors were making
headway in the consumer market. I've got a smallish (about 12-inch
screen) '60's "portable" (has a handle on top) color TV with
compactrons in it. (sorry, more than you wanted to know)
14. What magnitudes of voltages are required for operating the following
devices: Neon bulb,
about 90V
Xenon flashtube, Geiger-Mueller tube, Esaki diode.
15. What IF frequencies are traditional in the US for AM broadcast, FM
broadcast, TV sound, TV picture?
455kHz, 10.7MHz, dunno, dunno but I recall the IF bandwidth is
about 5MHz. Do I get partial credit?
[2004 aside, for any who haven't heard this: European engineers have
quipped for decades that TV signal format acronyms stood in the US for
"Never The Same Color" and in France for "Système Envelloper Contre les
AMéricains."]
16. What is a Hartley oscillator? A Colpitts oscillator? A Pierce
oscillator? A Wien-bridge oscillator? A blocking oscillator?
17. Quick, without calculation: What voltage corresponds to zero dBm in a
600-ohm circuit?
About 0.7V, because I actually did the calculation when designing a
modem a few years back. I also hang out on rec.audio.pro where these
values are often discussed.
18. What is an Eccles-Jordan circuit? A polyflop? A switch-tail ring
counter? A Johnson counter? An AC-coupled flip-flop?
19. In the context of filters, what, formally, does "biquad" mean? (1988
note: Most engineers get this wrong.)
20. What does it mean when a resistor is marked with bands
red-yellow-green-silver? A capacitor with "104K?"
2.7 meg, 10 percent tolerance. For the cap, 104 is 10 followed by 4
zeros in picofarads, or 0.1 uF. I forget what K is.
21. If an aluminum electrolytic capacitor is rated for "working voltage" of
10 volts, in what range of voltages is it designed to operate?
Between about 5 and 10 volts. I want to see other responses to this
one.
22. Roughly compare ceramic, polystyrene, and polycarbonate capacitors.
I like Jan's answer, but I can tell you this, they all generally
have less capacitance than Electrolytics.
Actually, these are caps made of the named dielectrics, and
ceramics really suck. They're temperature-sensitive (though you can
specify which way and by how much, useful in compensating for the
temperature drift in crystal oscillators), and they're microphonic
(mechanically shock them and a voltage spike comes out). I'm sure
there's more bad stuff about them that I can't think of at the moment.
23. What is a "2 1/2 D" core memory plane? (You could not open a computer
trade magazine in, say, 1968 without seeing incessant references to them.)
24. What is a couplate? A micromodule? Difference between thin-film and
thick-film hybrid circuits?
[1988 questions 25 and 26 concerned memory of the Ovonic Devices publicity
and business acronyms and were pretty far afield even in 1988; omitted now.]
It's tempting to deja-google for the 1988 post.
Speaking of "business acronyms" what does VAR mean in electrical
engineering, and in business? (yes I know both) I recall some years
ago an editorial, possibly in EE Times, discussing both meanings and
railing against the business use.
Registered trademarks mentioned herein are identified indirectly by context,
for clarity and because this is a trivia quiz.
Copyright 1988, 2004 by Max W. Hauser. All rights reserved. Past shameless
exploitations of author's 1979 MIT "Bag of Tricks" notes and other
engineering writings do not preclude copyright enforcement for this or other
work.
Geez, I hope it's okay to copy this back to Usenet on the followup
group, with answers/guesses interspersed. Does this fall under fair
use? :-/
