M
Max Hauser
Lots of old farts here these days, it seems. Here are answers from 16 years
ago, updated and supplemented. End notes include information references
that some people may find useful some time. (Note on date confusion: The
quiz was written in 1986 and first posted to sci.electronics 1987, contrary
to my earlier claim of 1988 which was based on the date of a file I had,
likely a re-posting.)
1. Assuming that you are acquainted with the "cascode" configuration, do you
know where the term came from?
A cascode amplifier has one device "stacked" on another (as in
collector-to-emitter, or plate-to-cathode). An appealing explanation of the
term, promoted in the 1980s by people I know and also reasoned out by
respondents here, is that it came from CASCading one amplifying triode
(valve) into the cathODE of another. That however is nothing like the
explanation by Hunt and Hickman (1939), the earliest coinage that I or
anyone I've read has located (and which claims explicitly to coin "cascode"
as a new word). The term appears in a long comparison of triode, tetrode,
pentode, and "cascode" tubes in DC voltage regulators. Hunt and Hickman
applied the nickname as if it designated another or "virtual" type of tube.
More detail in [Note 1] at the end.
2. What is a reflex amplifier?
A circuit that simultaneously amplifies two or more independent signals in
separate frequency bands. Used in RF receivers and TVs to amplify a
high-frequency signal and then, after detection, run the audio back through
the same tube, separating the signals via their different frequency ranges.
Led to optimal designs in technologies where the active components were very
expensive (as with tubes and early transistors).
3. What is the basic principle of a superhet receiver? of a regenerative
receiver? The difference between a mixer and a converter (in RF)?
Superheterodyne: Intermodulate an incoming RF signal with a tunable local
oscillator to yield a frequency-translated signal at an "intermediate"
frequency (IF); this can then be filtered for selectivity and sensitivity by
a *fixed* tuned-amplifier chain (see #15) [Note2]
Regenerative: positive feedback in a simple amplifier stage increases gain.
A mixer combines two signals to produce beat frequencies; it approximates an
ideal of multiplying the voltage waveforms. A converter is a
self-oscillating mixer that generates its own reference frequency. Five-grid
tubes (heptodes) were sometimes used; more recently [1987], multiple-gate
MOSFETs.
4. Who developed the op amp, and when?
Electronic amplifiers used in feedback loops to simulate other things
(electronic analog computation) appeared about 1938. That, by the way, is
how the term "analog" infiltrated electronics; earlier one heard of power,
audio, radio, and occasionally pulse and "switching" electronics. But the
op amp as a practical and familiar device is largely credited to George A.
Philbrick and Loebe Julie from the 1940s onward [Note 3].
5. What is the "purple plague"?
One of a class of parasitic alloys of gold and aluminum that can form on IC
wire bonds and impair reliability. It was a major chip reliability problem
in bipolar-technology parts circa 1970.
6. What is a class-C amplifier and where is it typically used?
An amplifying device operating in class C (as opposed to A, AB, B, D, E, F,
S, X, etc. etc. etc.) is defined as conducting current for less than 50% of
a sinusoidal cycle. Normally used in tuned power amplifiers, where a
resonant load circuit maintains output-waveform integrity despite the
distorted current waveform in the active device. Many AM transmitters
employed class-C power stages (to which modulation was applied by varying
the power supply.) [Original answer continued with gentle jab at a
late-1970s fashion for naming obscurely-different and rarely-used new
amplification "classes."]
7. Can you describe a tunnel diode? A unijunction transistor? An SCS? (What
is the basic principle of each and what are they used for.)
The tunnel (Esaki) diode (the 1N3712 series was famous, from General
Electric I believe): low-voltage incremental-negative-resistance device
based on a heavily-doped PN junction with a very thin depletion region.
Although it never fulfilled initial high hopes as an important switching
element, there is still nothing handier if you need to make a low-power VHF
transmitter the size of a pencil eraser. The tunnel diode, like the
transistor, is one of those devices that (a) occasioned a Nobel prize and
(b) had actually existed much earlier than widely assumed, but was believed
useless by earlier discoverers. (I have more info on that.)
Unijunction transistors are three-terminal (base-1, base-2, emitter)
negative-resistance devices where the emitter conducts current in a range of
voltages set by the bias on the two bases. Commonly used as a threshold
sensor or relaxation oscillator. The Semiconductor Controlled Switch is a
four-layer (PNPN) device like the Semiconductor Controlled Rectifier (SCR)
but with its gate electrode at the N mid-layer instead of the P, and
optimized for control rather than power-switching applications. The SCS is
now often lumped together under the name SCR.
8. Traditional op-amp ICs were designed whenever possible to run on +- 15
volts. Why that voltage?
Allowing a clean output swing of +- 10V, a convenient scale for their
original service as analog-computer computation elements. Vaccuum-tube op
amps set the trend earlier with +- 100V standard output swings. See also
Note 3 on op amps.
9. What do the following acronyms stand for: PDP, VAX, ASCII, EBCDIC, PRV,
BFO, RTTY, CW, VSB, VOR, Conelrad?
Programmed Data Processor (of course!); Virtual Address eXtension; American
Standard Code for Information Interchange; Extended Binary-Coded Decimal
Information Code; Peak Return Voltage; Beat-Frequency Oscillator;
RadioTeleTYpe; Continuous-Wave; Vestigial-SideBand; VHFOmnidirectional
Range; Plan for CONtrol of ELectromagnetic RADiation [Note 4]. I believe
that "PDP" is not now the "household" word it was in 1986 when this quiz
originally appeared, but it still is among old farts. In 1973, according to
DEC's advertising at the time, one-third of the world's computers were
PDP-8s.
10. What was revolutionary about the 741 op amp?
It was the first major IC op amp fully self-contained; it required no
external components for AC stability. As Jim Roberge pointed out in his
text on op amps, the particular frequency compensation built into the uA741
was performance-limiting for many non-DC applications, but it was simple to
use and it sold anyway.
11. Can you specifically describe the commercial semiconductor devices known
by the following terms: 1N34, CK722, 2N107, 2N998, 2N1304, 2N2222, 2N3055,
U222, uL900, uL958, uA703, uA709, SN7300 series, SUHL, CCSL, HTL, ECCSL,
Utilogic, COSMOS, Intel 1101, Intel 1702.
High points: 1N34, ubiquitous glass-packaged germanium signal diode; 2N998,
TO-18-packaged Darlington transistor pair; U222, early power RF junction
FET, handy but expensive; uL900, Fairchild RTL buffer chip (very SSI logic);
uL958, Fairchild early decade-counter chip (one of the classic "MSI"
circuits); 703, Fairchild RF amplifier chip; 709, Fairchild op-amp chip
(1964), hardly the first monolithic op amp but perhaps the first that was
really successful and competed with discrete-component designs. SN7300
series, TI DTL logic family, later eclipsed by TI's durable 7400 TTL family;
SUHL, Sylvania Universal High-Level Logic, and CCSL, Fairchild's Compatible
Current-Sinking Logic DTL-TTL family, both contenders in late 1960s for the
industry-standard status that finally fell to TI's 5400/7400 series; ECCSL,
Emitter-Coupled Current-Steered Logic, an ECL family from (?) RCA; Utilogic,
Signetics's offbeat SSI-MSI logic family with a mix of circuit types and
native gates of all four types; COSMOS, RCA's 1960s trademark for its
pioneering COmplementary-Symmetry MOS (later "CMOS") logic -- the original
CMOS; 1101, original MOS static RAM from Intel (256 bits, high-threshold
PMOS technology).
Extra Credit: "Signetics" was originally an acronym. Standing for?
12. Can you identify the following trademarks: Nixie, Pixie, Numitron?
The Nixie, as discussed on this newsgroup [as of 1987], is a neon glow tube
with glowing cathodes shaped like characters. The Pixie, its predecessor
and a much better article of old-fartness, had a disk anode visible from the
front with holes cut out in the shape of characters; glowing cathodes behind
them illuminated the desired character. Both are Burroughs trademarks.
Numitron was RCA's trademark for its hot-wire incandescent seven-segment
displays, popular circa 1970 but largely supplanted by LEDs and other
more-recently-perfected technologies.
13. What is a thyratron? a magic-eye tube? a compactron?
Thyratrons are hot-cathode gas-filled tubes that latch in response to a gate
signal, predecessors of PNPN devices. Used mainly in switching and
power-control applications. [In the original I predicted that they might be
useful again in switching (class-D) audio amplifiers for resolute
vaccuum-tube enthusiasts.] Some vaccuum-tube and hybrid digital computers,
such as the Sperry (?) SS-90, employed thyratrons as registers. A magic-eye
tube, for the benefit of anyone missing the earlier [1987] discussion on the
net, is an end-viewed fluorescent analog display used often as a level
indicator. Compactrons are a class of late miniature tubes, common through
the early 1970s, with lots of independent devices within each bottle, and
large pin counts.
14. What magnitudes of voltage(s) are required for operating the following
devices: neon bulb; Xenon flashtube; Geiger-Mueller tube, Esaki diode
Neon bulb, around 100V; Xenon flashtude, 200-300V for small ones, and a
trigger pulse of a few kV; G-M tube, 400-600V; Esaki (tunnel) diode,
hundreds of millivolts.
15. What IF frequencies are commonly used in the US for AM broadcast, FM
broadcast, TV sound, TV picture?
455 kHz; 10.7 MHz; 4.5 MHz; 45 MHz. See #3 for definition of IF.
16. What is a Hartley oscillator? a Colpitts oscillator? a Pierce
oscillator? a Wien-bridge oscillator? a blocking oscillator?
Hartley, LC sinusoidal oscillator with tapped coil; Colpitts, LC sinusoidal
oscillator with capacitive voltage divider; Pierce, a crystal or LC-tank
oscillator; and the Wien-bridge type, an RC sinusoidal oscillator. The
blocking oscillator is an RL oscillator typically used for timing at
sub-megahertz rates and usually realized with a transformer and a single
active device (transistor or tube).
17. Quick, without calculation: What voltage corresponds to zero dBm in a
600-ohm circuit?
0.775 V (the voltage corresponding to 1 mW in 600 ohms). This is a standard
reference value for classic 600-ohm professional audio circuits.
18. What is an Eccles-Jordan circuit? A polyflop? A switch-tail ring
counter? A Johnson counter? An AC-coupled flip-flop?
The Eccles-Jordan multivibrator is the original flip-flop, built with
vaccuum tubes. It is exactly the kind of device to which the IEEE _Spectrum_
devotes those nostalgic, elegiac articles for which it is lately [1987] so
well known. A polyflop is a generalization of the flip-flop, with more than
two outputs, only one of which is "on" at any time. It can be constructed
by cross-connecting NAND or NOR gates with as many inputs as gates.
A switch-tail ring counter or Johnson counter is a counter formed of a shift
register with its output inverted and fed to its input. In practice, it is
usually safer to gate all of the outputs back to the input so that the
circuit can recover if it enters an undesired state. AC-coupled flip-flops
are edge-triggered flip-flops whose clock input is capacitively coupled.
Common in two-valve or two-transistor discrete FF's, of the Eccles-Jordan
type, this method was also used in some bipolar monolithic FFs.
19. In the context of filters, what is a biquad? [1987 Note: most engineers
get this wrong.]
A biquad is any block that realizes a biquadratic transfer function (i.e.,
numerator and denominator are quadratic polynomials in s [for continuous
time] or in z to the -1 [for discrete time]). Many analog people think it
means a specific op-amp-based circuit that is actually only one
implementation.
20. What does it mean when a resistor is marked with bands
red-yellow-green-silver? a capacitor with letters "104K"?
2400000 ohms ["245"], 10% tolerance; 100000pF (0.1 uF), 10% tolerance [Note
5]
21. If an aluminum [UK: aluminium] electrolytic capacitor is rated for a
"working voltage" of 10 volts, in what range of voltages is it designed to
operate?
Not more, but more importantly not much less, than 10 volts. Five volts,
probably OK; two volts, it may not form the dielectric layer reliably.
[That was old wisdom. Modern experts here will if necessary correct me, I
feel confident.]
22. Roughly compare ceramic, polystyrene, and polycarbonate capacitors.
[1987] I posted separately on this earlier, but briefly, ceramic caps are
cheap, compact, wideband and not very precise; polystyrene are cheap,
stable, have very high leakage resistance, and have the larger inductance
characteristic of wound-film rather than sandwich construction; polycarb are
similar to polystyrene but extremely value-stable and expensive.
23. What is a "2 1/2 D" core memory plane?
It's a magnetic-core array of a particular wiring configuration. If the term
is familiar at all, then you remember computers from the Glory Days (IBM
1620, Univac 1108), when computers looked like proper Computers.
24. What is a couplate? a micromodule? the difference between thin-film and
thick-film hybrid circuits?
Thin-film hybrid circuits contain components (resistors, capacitors, wiring)
deposited with a screening process onto a ceramic substrate. In thick-film
hybrids, the components are discrete but leadless and they are attached to a
ceramic substrate after separate fabrication. In both cases, transistor and
IC dice also get attached after separate fabrication. These circuits are
called "hybrid" because they mix discrete-component and integrated-circuit t
echnologies.
Couplates and micromodules are two examples of thin-film hybrids: couplates
(Sprague TM?) were RC interstage coupling networks in capacitor-like
multilead packages; micromodules (IBM term) were digital logic circuits, to
be installed on small PC cards, and heavily used in the 360 (?) series of
mainframe computers.
Note 1: Cascode name
Quotation from the Hunt - Hickman 1939 survey paper coining a term new
"cascode." The relevant text concerns using simple high-gain voltage
amplifier stages for shunt output feedback in voltage regulators. (This
amplifier stage drives the grid of a series cathode follower serving as the
regulator -- standard stuff, still used.) Figure 12(a) shows a triode or
pentode tube as the feedback amplifier, Figure 12(b) a cascode, with a
footnote 14 explicitly coining the term:
This tube connection we have called the "cascode" and,
although somewhat unconventional, it is generally useful
for d. c. amplifier work in which it is inconvenient to supply
the additional bias voltages for a pentode. The dual
triode [used as cascode], as connected, may be shown to
be equivalent to a single triode having an amplification
factor of (u2 + u3 + u2u3) [subscripted] and a plate
resistance of (rp3 + (u3 + 1)rp2), where the subscripts
2 and 3 refer to the lower and upper portions of the
[cascode] tube, respectively. These coefficients must be
evaluated for the existing voltage distributions between the
two sections and experiments indicate that the effective
amplification factor for a type 6C8G tube is approximately
1300 with a plate resistance of 3 to 5 megohms.
That is the complete footnote and it appears amid a long comparison of the
behavior of triode, tetrode, pentode, and "cascode" tubes in DC voltage
regulators. Hunt and Hickman applied the nickname as if it designated
another type of tube. Hunt and Hickman, "On electronic voltage
stabilizers," _Review of Scientific Instruments_ vol. 10 no. 1 pp. 6-21,
January 1939. Coinage of "cascode" and explanation appear on page 16
including footnote 14. By the way, Hunt and Hickman stress this
configuration's "extreme versatility for low voltage (130-600)
applications." Low voltage capability was important, then as now!
There is an account of William Hewlett (famous for a brief student thesis
proposing a new practical RC-based lab oscillator whose merit was a mass of
14 pounds compared to existing technology at 93 pounds, and later
commercialized) late in his life, touring a lab and being asked by an
engineer, "Bill, who invented the cascode configuration?" and answering at
once "Hunt and Hickman." Their work was contemporaneous with his thesis.
In November 1999 I was contacted for historical material on early DC
amplifiers for the latest revision of a respected analog IC design text. I
forwarded the requested information and also a reference to this
Hunt-Hickman "cascode" article. For some reason the correspondence got lost
and instead, the new edition contains the apparently apocryphal "Cascade
into cathode" explanation instead. This will likely be revised later, since
I discussed it with the authors in person in October 2002.
Note 2: Superheterodyne
About 1972 I built an "inductorless" superhet AM radio using 160kHz active
filters for the tuned IF amplifier (Sallen-Key bandpass sections from
Darlington transistors and twin-tee RC networks). That was before recent
fashionable talk of "software-defined" radios. I await with interest the
announcement of the software TEM wave, software low-noise amp, software ADC,
PA, etc.
Note 3: Op amp origins
Julie and Philbrick (familiar names to analog specialists) commercialized
various pioneering analog amplifier and instrumentation techniques. They
collaborated on the famous K2-W (1952), known as the first mass-produced
modular op amp (plug-in octal-based case, two "miniature" tubes out the top,
and a two-gain-stage minor-loop frequency compensation that young engineers
today call "741 type"). All op amp collectors, including me, own K2-Ws, and
connoisseurs can tell you minor details from the case color. (By the way, I
recently acquired a Philbrick metal-case P65, the landmark early-1960s
solid-state op amp with the economical five- or six-transistor
three-gain-stage configuration that sustained the op-amp industry for a
decade.)
The term "operational" amplifier, referring of course to arithmetic
operations in analog computers, came from the 1947 analog-computation paper
by Ragazzini, Randall, and Russell. Philbrick and his firm promoted the
potential uses of the op amp. The firm's applications journal, the
_Lightning Empiricist,_ in the 1950s an 1960s -- supplemented periodically
by a bound Applications Manual -- more or less taught engineers what these
amplifiers can do and led to their acceptance outside computing. Many
people today cherish copies of these classy and seminal publications. In
the heyday of the Philbrick firm, its editor was Dan Sheingold and its head
of research was Bob Pease.
Many tidbits from the early days of the actual "analog" electronics industry
appear also in Jim William's first book (of two with similar titles):
_Analog Circuit Design: Art, Science, and Personalities,_
Butterworth-Heinemann 1991, ISBN 0750696400 (paper) or 0750691662
(acid-free). The high tide of analog computation (1950s-early 1960s)
produced at least two classic books rich with accumulated technique and
wisdom sometimes applicable in new ways: Jackson's _Analog Computation_
(1960) and Korn, later Korn and Korn, _Electronic Analog and Hybrid
Computers_ (two editions, 1964 and 1972).
Note 4: Conelrad
After the second world war and especially after 1949 (you DO know why that
date, don't you?) the US became newly concerned about domestic air defense.
A guidance method for hostile air fleets of "any aggressor," as Eisenhower
called Stalin, was navigation via known locations of broadcast radio
stations. Conelrad was a plan to switch some of them off and the others to
640 or 1240 kHz to remain on the air. Hence, US-made AM-broadcast radio
tuning scales of the 1950s to middle 1960s showed small marks at 640 and
1240kHz to remind people. There was a little radio jingle to a nine-note
fanfare, remembered by people older than me:
"six-forty-twelve-forty-Conelrad!" I have a type WE300 telephone (square
base, heavy, contemporaneous) with an original label on the front:
When Civil Defense Sirens Sound
DO NOT USE TELEPHONE
Turn Radio to 640 or 1240
(When, in the 1960s, friends of my parents named their child Conrad and he
proceeded to make as much noise as a civil defense siren, he earned the
nickname Conelrad.)
Note 5:
I never expected the creative discussions that ensued here over mnemonic
systems to memorize the color code, partly because I've never seen anyone
use them, who works with color-coded resistors a lot; you just learn the
colors. Which are in a natural spectrum order anyway and so easy to
remember.
Original content Copyright 2004 by Max W. Hauser
ago, updated and supplemented. End notes include information references
that some people may find useful some time. (Note on date confusion: The
quiz was written in 1986 and first posted to sci.electronics 1987, contrary
to my earlier claim of 1988 which was based on the date of a file I had,
likely a re-posting.)
1. Assuming that you are acquainted with the "cascode" configuration, do you
know where the term came from?
A cascode amplifier has one device "stacked" on another (as in
collector-to-emitter, or plate-to-cathode). An appealing explanation of the
term, promoted in the 1980s by people I know and also reasoned out by
respondents here, is that it came from CASCading one amplifying triode
(valve) into the cathODE of another. That however is nothing like the
explanation by Hunt and Hickman (1939), the earliest coinage that I or
anyone I've read has located (and which claims explicitly to coin "cascode"
as a new word). The term appears in a long comparison of triode, tetrode,
pentode, and "cascode" tubes in DC voltage regulators. Hunt and Hickman
applied the nickname as if it designated another or "virtual" type of tube.
More detail in [Note 1] at the end.
2. What is a reflex amplifier?
A circuit that simultaneously amplifies two or more independent signals in
separate frequency bands. Used in RF receivers and TVs to amplify a
high-frequency signal and then, after detection, run the audio back through
the same tube, separating the signals via their different frequency ranges.
Led to optimal designs in technologies where the active components were very
expensive (as with tubes and early transistors).
3. What is the basic principle of a superhet receiver? of a regenerative
receiver? The difference between a mixer and a converter (in RF)?
Superheterodyne: Intermodulate an incoming RF signal with a tunable local
oscillator to yield a frequency-translated signal at an "intermediate"
frequency (IF); this can then be filtered for selectivity and sensitivity by
a *fixed* tuned-amplifier chain (see #15) [Note2]
Regenerative: positive feedback in a simple amplifier stage increases gain.
A mixer combines two signals to produce beat frequencies; it approximates an
ideal of multiplying the voltage waveforms. A converter is a
self-oscillating mixer that generates its own reference frequency. Five-grid
tubes (heptodes) were sometimes used; more recently [1987], multiple-gate
MOSFETs.
4. Who developed the op amp, and when?
Electronic amplifiers used in feedback loops to simulate other things
(electronic analog computation) appeared about 1938. That, by the way, is
how the term "analog" infiltrated electronics; earlier one heard of power,
audio, radio, and occasionally pulse and "switching" electronics. But the
op amp as a practical and familiar device is largely credited to George A.
Philbrick and Loebe Julie from the 1940s onward [Note 3].
5. What is the "purple plague"?
One of a class of parasitic alloys of gold and aluminum that can form on IC
wire bonds and impair reliability. It was a major chip reliability problem
in bipolar-technology parts circa 1970.
6. What is a class-C amplifier and where is it typically used?
An amplifying device operating in class C (as opposed to A, AB, B, D, E, F,
S, X, etc. etc. etc.) is defined as conducting current for less than 50% of
a sinusoidal cycle. Normally used in tuned power amplifiers, where a
resonant load circuit maintains output-waveform integrity despite the
distorted current waveform in the active device. Many AM transmitters
employed class-C power stages (to which modulation was applied by varying
the power supply.) [Original answer continued with gentle jab at a
late-1970s fashion for naming obscurely-different and rarely-used new
amplification "classes."]
7. Can you describe a tunnel diode? A unijunction transistor? An SCS? (What
is the basic principle of each and what are they used for.)
The tunnel (Esaki) diode (the 1N3712 series was famous, from General
Electric I believe): low-voltage incremental-negative-resistance device
based on a heavily-doped PN junction with a very thin depletion region.
Although it never fulfilled initial high hopes as an important switching
element, there is still nothing handier if you need to make a low-power VHF
transmitter the size of a pencil eraser. The tunnel diode, like the
transistor, is one of those devices that (a) occasioned a Nobel prize and
(b) had actually existed much earlier than widely assumed, but was believed
useless by earlier discoverers. (I have more info on that.)
Unijunction transistors are three-terminal (base-1, base-2, emitter)
negative-resistance devices where the emitter conducts current in a range of
voltages set by the bias on the two bases. Commonly used as a threshold
sensor or relaxation oscillator. The Semiconductor Controlled Switch is a
four-layer (PNPN) device like the Semiconductor Controlled Rectifier (SCR)
but with its gate electrode at the N mid-layer instead of the P, and
optimized for control rather than power-switching applications. The SCS is
now often lumped together under the name SCR.
8. Traditional op-amp ICs were designed whenever possible to run on +- 15
volts. Why that voltage?
Allowing a clean output swing of +- 10V, a convenient scale for their
original service as analog-computer computation elements. Vaccuum-tube op
amps set the trend earlier with +- 100V standard output swings. See also
Note 3 on op amps.
9. What do the following acronyms stand for: PDP, VAX, ASCII, EBCDIC, PRV,
BFO, RTTY, CW, VSB, VOR, Conelrad?
Programmed Data Processor (of course!); Virtual Address eXtension; American
Standard Code for Information Interchange; Extended Binary-Coded Decimal
Information Code; Peak Return Voltage; Beat-Frequency Oscillator;
RadioTeleTYpe; Continuous-Wave; Vestigial-SideBand; VHFOmnidirectional
Range; Plan for CONtrol of ELectromagnetic RADiation [Note 4]. I believe
that "PDP" is not now the "household" word it was in 1986 when this quiz
originally appeared, but it still is among old farts. In 1973, according to
DEC's advertising at the time, one-third of the world's computers were
PDP-8s.
10. What was revolutionary about the 741 op amp?
It was the first major IC op amp fully self-contained; it required no
external components for AC stability. As Jim Roberge pointed out in his
text on op amps, the particular frequency compensation built into the uA741
was performance-limiting for many non-DC applications, but it was simple to
use and it sold anyway.
11. Can you specifically describe the commercial semiconductor devices known
by the following terms: 1N34, CK722, 2N107, 2N998, 2N1304, 2N2222, 2N3055,
U222, uL900, uL958, uA703, uA709, SN7300 series, SUHL, CCSL, HTL, ECCSL,
Utilogic, COSMOS, Intel 1101, Intel 1702.
High points: 1N34, ubiquitous glass-packaged germanium signal diode; 2N998,
TO-18-packaged Darlington transistor pair; U222, early power RF junction
FET, handy but expensive; uL900, Fairchild RTL buffer chip (very SSI logic);
uL958, Fairchild early decade-counter chip (one of the classic "MSI"
circuits); 703, Fairchild RF amplifier chip; 709, Fairchild op-amp chip
(1964), hardly the first monolithic op amp but perhaps the first that was
really successful and competed with discrete-component designs. SN7300
series, TI DTL logic family, later eclipsed by TI's durable 7400 TTL family;
SUHL, Sylvania Universal High-Level Logic, and CCSL, Fairchild's Compatible
Current-Sinking Logic DTL-TTL family, both contenders in late 1960s for the
industry-standard status that finally fell to TI's 5400/7400 series; ECCSL,
Emitter-Coupled Current-Steered Logic, an ECL family from (?) RCA; Utilogic,
Signetics's offbeat SSI-MSI logic family with a mix of circuit types and
native gates of all four types; COSMOS, RCA's 1960s trademark for its
pioneering COmplementary-Symmetry MOS (later "CMOS") logic -- the original
CMOS; 1101, original MOS static RAM from Intel (256 bits, high-threshold
PMOS technology).
Extra Credit: "Signetics" was originally an acronym. Standing for?
12. Can you identify the following trademarks: Nixie, Pixie, Numitron?
The Nixie, as discussed on this newsgroup [as of 1987], is a neon glow tube
with glowing cathodes shaped like characters. The Pixie, its predecessor
and a much better article of old-fartness, had a disk anode visible from the
front with holes cut out in the shape of characters; glowing cathodes behind
them illuminated the desired character. Both are Burroughs trademarks.
Numitron was RCA's trademark for its hot-wire incandescent seven-segment
displays, popular circa 1970 but largely supplanted by LEDs and other
more-recently-perfected technologies.
13. What is a thyratron? a magic-eye tube? a compactron?
Thyratrons are hot-cathode gas-filled tubes that latch in response to a gate
signal, predecessors of PNPN devices. Used mainly in switching and
power-control applications. [In the original I predicted that they might be
useful again in switching (class-D) audio amplifiers for resolute
vaccuum-tube enthusiasts.] Some vaccuum-tube and hybrid digital computers,
such as the Sperry (?) SS-90, employed thyratrons as registers. A magic-eye
tube, for the benefit of anyone missing the earlier [1987] discussion on the
net, is an end-viewed fluorescent analog display used often as a level
indicator. Compactrons are a class of late miniature tubes, common through
the early 1970s, with lots of independent devices within each bottle, and
large pin counts.
14. What magnitudes of voltage(s) are required for operating the following
devices: neon bulb; Xenon flashtube; Geiger-Mueller tube, Esaki diode
Neon bulb, around 100V; Xenon flashtude, 200-300V for small ones, and a
trigger pulse of a few kV; G-M tube, 400-600V; Esaki (tunnel) diode,
hundreds of millivolts.
15. What IF frequencies are commonly used in the US for AM broadcast, FM
broadcast, TV sound, TV picture?
455 kHz; 10.7 MHz; 4.5 MHz; 45 MHz. See #3 for definition of IF.
16. What is a Hartley oscillator? a Colpitts oscillator? a Pierce
oscillator? a Wien-bridge oscillator? a blocking oscillator?
Hartley, LC sinusoidal oscillator with tapped coil; Colpitts, LC sinusoidal
oscillator with capacitive voltage divider; Pierce, a crystal or LC-tank
oscillator; and the Wien-bridge type, an RC sinusoidal oscillator. The
blocking oscillator is an RL oscillator typically used for timing at
sub-megahertz rates and usually realized with a transformer and a single
active device (transistor or tube).
17. Quick, without calculation: What voltage corresponds to zero dBm in a
600-ohm circuit?
0.775 V (the voltage corresponding to 1 mW in 600 ohms). This is a standard
reference value for classic 600-ohm professional audio circuits.
18. What is an Eccles-Jordan circuit? A polyflop? A switch-tail ring
counter? A Johnson counter? An AC-coupled flip-flop?
The Eccles-Jordan multivibrator is the original flip-flop, built with
vaccuum tubes. It is exactly the kind of device to which the IEEE _Spectrum_
devotes those nostalgic, elegiac articles for which it is lately [1987] so
well known. A polyflop is a generalization of the flip-flop, with more than
two outputs, only one of which is "on" at any time. It can be constructed
by cross-connecting NAND or NOR gates with as many inputs as gates.
A switch-tail ring counter or Johnson counter is a counter formed of a shift
register with its output inverted and fed to its input. In practice, it is
usually safer to gate all of the outputs back to the input so that the
circuit can recover if it enters an undesired state. AC-coupled flip-flops
are edge-triggered flip-flops whose clock input is capacitively coupled.
Common in two-valve or two-transistor discrete FF's, of the Eccles-Jordan
type, this method was also used in some bipolar monolithic FFs.
19. In the context of filters, what is a biquad? [1987 Note: most engineers
get this wrong.]
A biquad is any block that realizes a biquadratic transfer function (i.e.,
numerator and denominator are quadratic polynomials in s [for continuous
time] or in z to the -1 [for discrete time]). Many analog people think it
means a specific op-amp-based circuit that is actually only one
implementation.
20. What does it mean when a resistor is marked with bands
red-yellow-green-silver? a capacitor with letters "104K"?
2400000 ohms ["245"], 10% tolerance; 100000pF (0.1 uF), 10% tolerance [Note
5]
21. If an aluminum [UK: aluminium] electrolytic capacitor is rated for a
"working voltage" of 10 volts, in what range of voltages is it designed to
operate?
Not more, but more importantly not much less, than 10 volts. Five volts,
probably OK; two volts, it may not form the dielectric layer reliably.
[That was old wisdom. Modern experts here will if necessary correct me, I
feel confident.]
22. Roughly compare ceramic, polystyrene, and polycarbonate capacitors.
[1987] I posted separately on this earlier, but briefly, ceramic caps are
cheap, compact, wideband and not very precise; polystyrene are cheap,
stable, have very high leakage resistance, and have the larger inductance
characteristic of wound-film rather than sandwich construction; polycarb are
similar to polystyrene but extremely value-stable and expensive.
23. What is a "2 1/2 D" core memory plane?
It's a magnetic-core array of a particular wiring configuration. If the term
is familiar at all, then you remember computers from the Glory Days (IBM
1620, Univac 1108), when computers looked like proper Computers.
24. What is a couplate? a micromodule? the difference between thin-film and
thick-film hybrid circuits?
Thin-film hybrid circuits contain components (resistors, capacitors, wiring)
deposited with a screening process onto a ceramic substrate. In thick-film
hybrids, the components are discrete but leadless and they are attached to a
ceramic substrate after separate fabrication. In both cases, transistor and
IC dice also get attached after separate fabrication. These circuits are
called "hybrid" because they mix discrete-component and integrated-circuit t
echnologies.
Couplates and micromodules are two examples of thin-film hybrids: couplates
(Sprague TM?) were RC interstage coupling networks in capacitor-like
multilead packages; micromodules (IBM term) were digital logic circuits, to
be installed on small PC cards, and heavily used in the 360 (?) series of
mainframe computers.
Note 1: Cascode name
Quotation from the Hunt - Hickman 1939 survey paper coining a term new
"cascode." The relevant text concerns using simple high-gain voltage
amplifier stages for shunt output feedback in voltage regulators. (This
amplifier stage drives the grid of a series cathode follower serving as the
regulator -- standard stuff, still used.) Figure 12(a) shows a triode or
pentode tube as the feedback amplifier, Figure 12(b) a cascode, with a
footnote 14 explicitly coining the term:
This tube connection we have called the "cascode" and,
although somewhat unconventional, it is generally useful
for d. c. amplifier work in which it is inconvenient to supply
the additional bias voltages for a pentode. The dual
triode [used as cascode], as connected, may be shown to
be equivalent to a single triode having an amplification
factor of (u2 + u3 + u2u3) [subscripted] and a plate
resistance of (rp3 + (u3 + 1)rp2), where the subscripts
2 and 3 refer to the lower and upper portions of the
[cascode] tube, respectively. These coefficients must be
evaluated for the existing voltage distributions between the
two sections and experiments indicate that the effective
amplification factor for a type 6C8G tube is approximately
1300 with a plate resistance of 3 to 5 megohms.
That is the complete footnote and it appears amid a long comparison of the
behavior of triode, tetrode, pentode, and "cascode" tubes in DC voltage
regulators. Hunt and Hickman applied the nickname as if it designated
another type of tube. Hunt and Hickman, "On electronic voltage
stabilizers," _Review of Scientific Instruments_ vol. 10 no. 1 pp. 6-21,
January 1939. Coinage of "cascode" and explanation appear on page 16
including footnote 14. By the way, Hunt and Hickman stress this
configuration's "extreme versatility for low voltage (130-600)
applications." Low voltage capability was important, then as now!
There is an account of William Hewlett (famous for a brief student thesis
proposing a new practical RC-based lab oscillator whose merit was a mass of
14 pounds compared to existing technology at 93 pounds, and later
commercialized) late in his life, touring a lab and being asked by an
engineer, "Bill, who invented the cascode configuration?" and answering at
once "Hunt and Hickman." Their work was contemporaneous with his thesis.
In November 1999 I was contacted for historical material on early DC
amplifiers for the latest revision of a respected analog IC design text. I
forwarded the requested information and also a reference to this
Hunt-Hickman "cascode" article. For some reason the correspondence got lost
and instead, the new edition contains the apparently apocryphal "Cascade
into cathode" explanation instead. This will likely be revised later, since
I discussed it with the authors in person in October 2002.
Note 2: Superheterodyne
About 1972 I built an "inductorless" superhet AM radio using 160kHz active
filters for the tuned IF amplifier (Sallen-Key bandpass sections from
Darlington transistors and twin-tee RC networks). That was before recent
fashionable talk of "software-defined" radios. I await with interest the
announcement of the software TEM wave, software low-noise amp, software ADC,
PA, etc.
Note 3: Op amp origins
Julie and Philbrick (familiar names to analog specialists) commercialized
various pioneering analog amplifier and instrumentation techniques. They
collaborated on the famous K2-W (1952), known as the first mass-produced
modular op amp (plug-in octal-based case, two "miniature" tubes out the top,
and a two-gain-stage minor-loop frequency compensation that young engineers
today call "741 type"). All op amp collectors, including me, own K2-Ws, and
connoisseurs can tell you minor details from the case color. (By the way, I
recently acquired a Philbrick metal-case P65, the landmark early-1960s
solid-state op amp with the economical five- or six-transistor
three-gain-stage configuration that sustained the op-amp industry for a
decade.)
The term "operational" amplifier, referring of course to arithmetic
operations in analog computers, came from the 1947 analog-computation paper
by Ragazzini, Randall, and Russell. Philbrick and his firm promoted the
potential uses of the op amp. The firm's applications journal, the
_Lightning Empiricist,_ in the 1950s an 1960s -- supplemented periodically
by a bound Applications Manual -- more or less taught engineers what these
amplifiers can do and led to their acceptance outside computing. Many
people today cherish copies of these classy and seminal publications. In
the heyday of the Philbrick firm, its editor was Dan Sheingold and its head
of research was Bob Pease.
Many tidbits from the early days of the actual "analog" electronics industry
appear also in Jim William's first book (of two with similar titles):
_Analog Circuit Design: Art, Science, and Personalities,_
Butterworth-Heinemann 1991, ISBN 0750696400 (paper) or 0750691662
(acid-free). The high tide of analog computation (1950s-early 1960s)
produced at least two classic books rich with accumulated technique and
wisdom sometimes applicable in new ways: Jackson's _Analog Computation_
(1960) and Korn, later Korn and Korn, _Electronic Analog and Hybrid
Computers_ (two editions, 1964 and 1972).
Note 4: Conelrad
After the second world war and especially after 1949 (you DO know why that
date, don't you?) the US became newly concerned about domestic air defense.
A guidance method for hostile air fleets of "any aggressor," as Eisenhower
called Stalin, was navigation via known locations of broadcast radio
stations. Conelrad was a plan to switch some of them off and the others to
640 or 1240 kHz to remain on the air. Hence, US-made AM-broadcast radio
tuning scales of the 1950s to middle 1960s showed small marks at 640 and
1240kHz to remind people. There was a little radio jingle to a nine-note
fanfare, remembered by people older than me:
"six-forty-twelve-forty-Conelrad!" I have a type WE300 telephone (square
base, heavy, contemporaneous) with an original label on the front:
When Civil Defense Sirens Sound
DO NOT USE TELEPHONE
Turn Radio to 640 or 1240
(When, in the 1960s, friends of my parents named their child Conrad and he
proceeded to make as much noise as a civil defense siren, he earned the
nickname Conelrad.)
Note 5:
I never expected the creative discussions that ensued here over mnemonic
systems to memorize the color code, partly because I've never seen anyone
use them, who works with color-coded resistors a lot; you just learn the
colors. Which are in a natural spectrum order anyway and so easy to
remember.
Original content Copyright 2004 by Max W. Hauser
