- AC [Wechselstrom / Wechselspannung] - I should rewrite this paragraph.
- Alternating Current. In a time/voltage diagram, AC
voltage represents a sine function (usually), or just any periodically
alternating function. The mains voltage is AC voltage,
for example.
- Active high / active low [High-aktiv/Low-aktiv]
- Normally, signals are active high, which means a
voltage level of
0V represents a logical 0 (LOW) and a voltage of above 5V represents a
logical 1 (HIGH). If, for example, an IC pin is named "CS"
(chip select), the chip is usually selected by pulling this line to HIGH (5V
for TTL), and it gets deselected by pulling it to LOW (0V).
This is when signals are active high. In
many cases, however, the signals are active low, e.g. the Commodore
serial bus lines carry active low signals,
so that, for instance, a serial reset is activated by pulling the reset line
from the default 5V level to 0V (LOW); and the data line carries 0-bits when
it is HIGH and 1-bits when it is LOW.
- ADC [A/D-Wandler]
- Analog-Digital Converter.
- Amperemeter
- Device for measuring electric current. Usually part of a
multimeter.
- AND [UND]
- Logical function which is TRUE if all inputs are TRUE.
A B | A AND B
-----+-------
0 0 | 0
0 1 | 0
1 0 | 0
1 1 | 1
Examples:
7408: 4 AND gates with 2 inputs each
7409: 4 AND gates with 2 inputs each, open collector
7421: 2 AND gates with 4 inputs each
4081: 4 CMOS AND gates with 2 inputs each
4081: 2 CMOS AND gates with 4 inputs each
- Buffer [Puffer / Treiber]
- Same as driver.
- Bus
- This is the name for a set of lines in a computer system fulfilling a
common function, e.g. the address bus and the data bus.
- Capacitance [Kapazität]
- Electrical entity which describes the amount of charge a
capacitor can store. Unit: farad (F).
- Capacitor [Kondensator]
- A capacitor is an electrical element which is capable of storing small
amounts of electrical energy, just like an accumulator.
The five most common capacitor types are:
- Styroflex capacitor
- High quality, little tolerance. Mainly employed in high-end
audio applications. Irrelevant for computer applications. Unpolarized.
- Electrolytic capacitor [Elektrolytkondensator, Elko]
- High capacities, polarized, bigger tolerances. Typical application:
filtering capacitor in power supplies. Typical capacity greater than 1uF.
- Ceramic capacitor [Keramikkondensator]
- Unpolarized. Typical capacity smaller than 1uF. The Dielectric consists
of ceramic layers. Widely used for all applications.
- Film capacitor [Folienkondensator] [or is this a FOIL capacitor?]
- Like ceramic, selfhealing, usually smaller tolerance range, as
ceramic, this type is widely used in all applications. Unpolarized.
Available for high voltages also (up to 1000V).
- Tantal (electrolytic) capacitor [Tantalkondensator, Tantal-Elko]
- Like electrolytic, smaller tolerance range, particularly used in digital
electronics. Polarized. Typical application: stabilizing. Rarely
available for higher voltages (> 10V) and higher capacities
(> 100uF) or at least very expensive then.
Since a simple capacitor only consists of two plates facing each other, you
can imagine that even two wires lying in parallel have a certain capacitance.
When you charge a capacitor by applying voltage to it, it first behaves like
a shortcut, then its resistance increases until no current flows through it
anymore. This shortcut period is also present in parallel wires, it drains
much power from the chip the wires are connected to, a good example is a
parallel cable for SpeedDOS, etc.,
or a printer cable attached to
the C64's userport: the longer the cable, the higher its capacitance, the
longer the shortcut period, the higher the current which the chip (the CIA
in this case) has to endure, and the shorter the chip's lifetime.
- Chip
- An IC with housing. The following types are common:
- DIL
- Dual In Line. This is the most widely used IC housing. The pins come
out on both sides of the chip. When the notch on the case points to
the top, pin 1 is in the upper left corner, the other pin
numbers are counted counter-clockwise.
- DIP
- DIL Package. 1) Same as DIL, 2) used in 'DIP switch', a set of small
switches in a chip like case.
- SIL
- Single In Line. They have pins on only one side of the case. SILs are
used on SIMMs (Single In line Memory Module) and SIPPs (Single In line
Package err... P... P... - I don't know, do you?).
- ZIP
- Zigzag In line Package. Like SILs, but the pins form a zigzag line.
VRAMs often come in ZIP housings.
- CMOS
- Complementary Metal Oxide Semiconductor. TTL uses bipolar
transistors, while CMOS chips use unipolar transistors (FETs)
which are connected complementarily (one p-mos, one n-mos), thus consuming
virtually no power and staying much cooler than appropriate TTL chips. Alas,
CMOS chips are not suitable for very high frequencies: when the input level
changes, supply voltage pin and GND get shortly short-circuited. The higher
the switch frequency, the higher the shortcut time. If you run CMOS chips at
high frequencies, most of the switching time there is a shortcut, resulting
in high power consumption and heat generation.
The switching thresholds are less than 30% (LOW) and greater than 70%
(HIGH) of the supply voltage.
As opposed to the TTL series (74xx), CMOS family chips are
not bound to 5V supply voltage. Vcc ranges from 3 to 18V (for the
4000 family). There are also TTL compatible CMOS families available, e.g.
the widely used 74HCxx series (voltage range 4-6V), where HC stands for
High speed Cmos..
- Composite video [BAS / FBAS]
- Video signal which comprises of color and brightness information as well
as horizontal and vertical synchronization information. Since the video chip's
output signals are mixed into one signal (the composite video signal) and then
must be split again in the monitor, losses occur and deteriorate the display
quality, often resulting in color schlieren (streaks). If possible, use the
computer's Chroma/Luma output, which carries brightness and sync information
on one line, but color information on another line, which eliminates the color
schlieren. The best result is achieved by using an RGB output.
- Conductor [Leiter]
- A material is called a conductor if electrons can move through it, in
other words, if it allows flow of electrical current.
How well current can flow through the conductor is determined by its
resistance. If the resistance is very high, the
material is called an insulator.
- Connector [Steckverbinder, Stecker]
-
- BNC
- Bajonett Nut Connector. Used for video connections, ethernet/arcnet,
and for high frequency measuring equipment
(oscilloscope, etc.).
- DB-xx [Sub-D, D-Sub]
- ? Used for: RS232C (DB9 or DB25 male), parallel port (DB25 female),
C128D keyboard connector (DB 25).
- DIN
- Deutsches Institut für Normung. Used for Commodore
serial bus
(6-pin), C64/C128/SX64 AV port
(8-pin, horseshoe shape), C64
power supply jack (7-pin, male) and for
MIDI connections.
- RCA [Cinch]
- Radio Company of America(?). Used for audio and video connections.
In Germany and probably other countries, too, this connector is
also known as 'cinch'. Can someone please tell me why?
- Continuity [Durchgang]
- A cable (or other conducting material) has continuity when it has
a low resistance, when it therefore constitutes a shortcut.
- Continuity tester [Durchgangsprüfer]
- Device for checking for continuity. It reacts to
a resistance below ~100ohm, normally accoustically; some devices have a
selectable threshold. Usually part of a multimeter.
Alas, many continuity testers beep already at a resistance of up to 300ohm,
including my own, and that is NOT the definition of shortcut. These devices
are only good for checking your xmas tree light chain or a simple cable; for
sophisticated electronics, a continuity tester is usually useless.
- Counter [Zähler]
- Counters are elements counting the number of clock signals and
outputting them as binary or decimal representation on the output pins.
Examples
4060: 14-step CMOS binary counter with internal oscillator circuit
7468: 2 asynchronous decimal counters
- Current [Strom]
- Electrical entity which is defined by the amount of charge flow
in Coulomb per second. Unit: ampere (A). 1 A = 1 C / 1 sec.
- DC [Gleichstrom / Gleichspannung]
- Direct current. DC voltage is linear and constant,
and either positive or negative. The same applies to direct current. See
also AC.
- DAC [D/A-Wandler]
- Digital-Analog Converter.
- Diode
- Semiconductor element which lets
current flow in only one direction (forward direction).
Current flows if a positive voltage greater than the forward voltage is
applied to the anode of the diode (the other end is called cathode and is
usually marked with a black ring on the case), otherwise, the diode has a
very high resistance. If the applied voltage is below the avalanche / blocking
voltage (which is always negative), the diode breaks down and constitutes a
shortcut.
The rarely used germanium diodes have a
forward voltage of 0.3V, while the standard silicon diode has a forward
voltage of 0.6V.
- Schottky diode
- Diode with a p-n junction consisting of metal and silicon [?].
It is used for applications requiring fast switching, for instance
ECL circuits.
- Zener diode [Z-Diode]
- As opposed to all other diodes, the Z diode is used in reverse
direction. It has a defined avalanche voltage and is often used for
voltage stabilizing.
Z diodes often have a blue, yellow or red base color. Common series
are BZXxx, ZPDxx, and BZYxx, where xx is the avalanche voltage, e.g.
ZPD4.7 or BZY9.1.
- Tunnel diode
- Only for very high frequency applications. Its function is not based
on the avalanche effect, but on the tunnel effect.
- DRAM
- Dynamic RAM. Not to be mixed up with a dram of whisky :-)
DRAM needs a continuous refresh, as the information in it is stored by
very small capacitors.
- Driver [Treiber]
- A driver's output level follows the input level if it is a non-inverting
type, and it implements a NOT function, if it is an
inverting type. Drivers are employed for
- increasing the maximum output current of logical signals.
- signal shaping - turn a noisy signal into a clean signal
- protecting expensive chips
Examples:
7404: hex inverter (6 inverters)
7414: hex inverter with Schmitt trigger inputs
7405: hex inverter with O.C. outputs
7406: inverting driver with O.C. outputs (30V)
7416: inverting driver with O.C. outputs (15V)
7407: non-inverting driver with O.C. outputs (30V)
7417: non-inverting driver with O.C. outputs (15V)
4069: inverting CMOS driver
4049: inverting CMOS driver, buffered
4050: CMOS driver
- ECL
- Emitter-Coupled-Logic. Daniel actually wanted to skip this, but
Mr. SID persuaded me to write something about it. Errm... wait :-)
- EEPROM
- Electrically EPROM. In contrast to EPROMs, EEPROMs
don't need exposure to UV light to be erased, but can be erased electrically.
A big advantage is that is accessed like an SRAM. Write accesses perform
an automatic clear before write and thus make writing EEPROMs as easy as
writing to SRAMs. Series designator: 28xx, where xx is the number of kbits stored.
Serial EEPROMs are labeled 24Cxx (8bit) or 93Cxx (16bit).
Low voltage eproms (PLCC): 3V (or 3.3V) are
labeled 27Vxx.
- Electron [Elektron]
- Doh!
- EPROM
- Erasable PROM. EPROMs allow the contents to be erased
by exposing its builtin window to UV light. After this process, all memory
cells contain $ff and the EPROM can be written again.
Series designator: 27xx, where xx is the number of kbits stored.
Links: AMD's Programming AMD's CMOS EPROMs [PDF, 42k]
- EXOR
- Logical function which is TRUE if and only if exactly one input is TRUE. Another
very common name for this function is XOR.
A B | A EXOR B
-----+-------
0 0 | 0
0 1 | 1
1 0 | 1
1 1 | 0
Examples:
7486 : 4 EXOR gates with 2 inputs each
74136: 4 EXOR gates with 2 inputs each, open collector
4070 : 4 CMOS EXOR gates with 2 inputs each
- FET
- Field Effect Transistor. As opposed to normal bipolar transistors, these
unipolar transistors have a neglectable flow of current through their gate
(bipolar: base), they consume virtually no power. NMOS-FETs
and PMOS-FETs can be coupled to form CMOS
circuits.
- Flash-EPROM
- An EEPROM which can only be written (and erased) in
whole banks.
Series designator: 28Fxxx (12 V prg. voltage), 29Fxxx (5 V prg. voltage),
and 29LVxxx/29SLxxx (3 V and below),
where xxx is the memory capacity: 010 - 1 Mbit, 020 - 2 Mbit, etc. If the
Flash-EPROM supports 16 bit organization, xxx is: 100 - 1 Mbit, 200 - 2 Mbit, etc.
- Flip-flop [Flipflop]
- This edge-triggered element has two stable states, which are toggled on different
events, depending on the type:
- D flip-flop
- Delay flip-flop. The input appears at the output delayed by one clock
cycle.
- T flip-flop
- Toggle flip-flop. The output alternates with each input signal change.
Funnily enough, I did not find this chip anywhere, although it is
mentioned in the "DUDEN Informatik", Dudenverlag. To simulate a T
flip-flop, you can simply connect a D flip-flop's complementary output
Q' with its input.
- JK flip-flop
- This type combines characteristics of of RS flip-flop and T flip-flop.
It has two inputs J and K and a clock input C. If different signals are
applied to J and K, the JK flip-flop acts like an RS flip-flop. If
J=K, it acts like a T flip-flop.
Viewed technically, a JK flip-flop comprises of two coupled flip-flops
(called Master and Slave), where one outputs the input signals on the
rising edge, the other one on the falling edge of the clock signal.
Therefore, it is sometimes called master slave flip-flop. Main
applications of the JK flip-flop are counters and
shift registers.
- RS flip-flop
- Reset-Set flip-flop. These have a reset input and a set input. If
reset is high, the output goes low, if set is high, the output goes
high. Setting both reset and set to high is forbidden, as the results
are indetermined.
Examples:
7470 : JK flip-flop with 3 inputs each, preset and reset
74L71: RS master slave flip-flop with 3 inputs each, preset and reset
74171: 4 D flip-flops with clear input
- Fuse [Sicherung]
- Little glass tube with a wire of defined maximum voltage and current
which protects a device from overvoltage and overcurrent.
There are two common formats: 5 x 20mm (German) and 6 x 30mm (American), the
latter is used in the C64. Sometimes (particularly with types for higher
currents) you cannot see the wire because the glass tube is filled with sand.
- Gate [Gatter]
- A gate is a circuit on a chip, which implements a logical function. A
7406, for example, contains 6 gates (non-inverting
drivers).
- IC
- Integrated Circuit. A set of gates etched on a silicon wafer. As ICs are
very sensitive, they get enclosed by a plastic or ceramic case, with their
inputs and outputs connected to little metal pins. An IC in this housing
is called chip. Often chips are called IC, too.
- Impedance [Impedanz]
- A few opinions about impedance:
Impedance is when
- you check an 8ohms loudspeaker with an ohmmeter and what you get is
6.7ohms,
- you apply a video signal to a radio antenna cable and the output
remains quiet,
- you put your turtle on the clothes-line and the
other day, your neigbor's cat is dead.
to be continued...
- Insulator [Isolator]
- A material which doesn't conduct electrical current.
The opposite is a conductor.
- Inverter
- Gate inverting a logical signal, thus implementing a
NOT function. For examples, see drivers.
- Latch [?]
- A set of flip-flops with a common clock signal.
In each cycle, they take the logical input signals over to their outputs.
Usually used to form multiplex address
busses. As opposed to flip-flops,
latches are level-triggered.
- LED [Leuchtdiode]
- An LED (Light Emitting Diode) is a diode emitting
light when operated in forward direction. Since it is a diode, it has a
nearly neglectible resistance and MUST be operated with a series
resistor.
The forward voltages depend on the type:
- Red
- 1.6 V-2.1 V. Series resistor for 5V: 330 ohm.
- Green
- 2.2 V-2.7 V. Series resistor for 5V: 270 ohm.
- Yellow
- 2.7 V-3.2 V. Series resistor for 5V: 270 ohm.
- Blue
- 3.3 V - 4.2 V. [Thanks to Matthias for this information]
While normal LEDs consume about 20mA, high efficiency LEDs require
only currents from 2-4mA (depending on type and color), which means that
you can directly connect them to standard logical outputs (74LSxx or CMOS
4000 series) without need of a driver. Nevertheless
you need an appropriate series resistor.
- Logic tester [Logiktester]
- Detects and indicates logic TTL (and/or)
CMOS voltage levels. It
usually contains a pulse memory (comprising a
flip-flop) that memorizes pulses too short
to be noticed otherwise.
- Mains voltage [Netzspannung]
- The voltage at the wall outlet.
Australia: 240V @ 50Hz
England : 230V @ 50Hz (formerly 240V) [?]
Germany : 230V / 400V @ 50Hz (formerly 220V / 380V)
Japan : 100V @ 75Hz (perverts!) [?]
USA : 120V / 240V @ 60Hz (ranges from 110V to 125V)
Note that since 1989, the new European voltage is 230V @ 50Hz
Do you live in one of the countries mentioned above and can verify the
information? Then mail me!
- Monoflop
- Also known as one-shot multivibrator. Flip-flop
with only one stable state. It remains in the unstable state for a
certain time determined by capacitors.
Examples:
74121: Monoflop with Schmitt trigger input
74221: 2 monoflops with Schmitt trigger input and reset
74122: Retriggerable monoflop with reset
74123: 2 retriggerable monoflops with reset
- MOS
- Metal Oxide Semiconductor.
- Multi emitter
-
- Multimeter
- An all-in-one measuring device. It combines a voltmeter,
an amperemeter and an ohmmeter
which usually also can act as
continuity tester.
Often it contains a transistor tester and measures capacities and
inductivities (in a small range). There are both analog and digital types,
the latter is the preferred choice.
- Multiplexing
-
- NAND [NUND - bah!]
- Logical function which is TRUE if and only if not all of the inputs are
TRUE.
A B | A NAND B
-----+---------
0 0 | 1
0 1 | 1
1 0 | 1
1 1 | 0
Examples:
7400: 4 NAND gates with 2 inputs each
7401: 4 NAND gates with 2 inputs each, open collector
7413: 2 NAND Schmitt triggers with 4 inputs each
7426: 4 NAND gates with 2 inputs each, open collector, 15V
4011: 4 CMOS NAND gates with 2 inputs each
4012: 2 CMOS NAND gates with 4 inputs each
4093: 4 CMOS NAND gates with 2 inputs each and Schmitt trigger
- Negative logic [Negative Logik]
- Negative logic means that the signals are active low.
- NMOS
- N-doped MOS.
- NOR [NODER - bah!]
- Logical function which is TRUE if and only if all inputs are FALSE.
A B | A NOR B
-----+---------
0 0 | 1
0 1 | 0
1 0 | 0
1 1 | 0
Examples:
7402: 4 NOR gates with 2 inputs each
7423: 2 NOR gates with 4 inputs each and strobe
4001: 4 CMOS NOR gates with 2 inputs each
4002: 2 CMOS NOR gates with 4 inputs each
- NOT [NICHT]
- Logical function which is TRUE if the input is FALSE.
A | NOT A
---+-------
0 | 1
1 | 0
Inverters implement this function.
- NTSC
- National Television Standard Code. Video encoding standard in
the United States and in Japan. NTSC has 60 pictures/sec and 526 lines
vertical resolution. [Thanks to Fungus for the info on the resolution]
- Ohmmeter
- Device for measuring resistance. Usually part of a
multimeter.
- Open collector
- A possible output connection of a TTL circuit. The output is
formed by a single transistor, which is not connected
to the
supply voltage, therefore an external connection to the supply
voltage (via a pull-up resistor) is required. Multiple
open collector outputs can be connected together, the outputs
carrying a 0 signal will override all other outputs.
- Oscilloscope [Oszilloskop]
- A sophisticated device which displays voltage curves graphically.
If you have one, you are either lucky or rich. Oscilloscope donations here, please :-)
- OR [ODER]
- Logical function which is TRUE if at least one input is TRUE.
A B | A OR B
-----+-------
0 0 | 0
0 1 | 1
1 0 | 1
1 1 | 1
Examples:
7432 : 4 OR gates with 2 inputs each
74832: 6 OR drivers with 2 inputs each
4071 : 4 CMOS OR gates with 2 inputs each
4072 : 2 CMOS OR gates with 4 inputs each
- PAL
- This acronym has two meanings:
- Phase-Alternation Lines. Video encoding standard used in
European countries. PAL has 50 pictures/sec interlaced and a
resolution of 625 lines [?].
- Programmable Array Logic. A chip which implements a sum-of-products
logic equation. A PAL can be programmed only once.
Type designator: xxyzz, where xx is the number of inputs, y is
either L for active low outputs or H for active high
outputs, and zz is the number of outputs; example: 16L8. A derivate [?]
is the PLA.
- PCB [Platine, Leiterplatte]
- Printed Circuit Board. This is the most professional way to
implement a circuit. The elements are put into the holes of the
photographically etched media and soldered on the opposite side.
When it is clear that the topic is not skate boards, PCBs are
shortly called 'board'.
- Photo diode
- Diode which is controlled by light.
- Photo transistor
- Transistor which is controlled by light.
- PLA
- Programmable Logic Array. AFAIR the same as a PAL, but
with a programmable OR matrix
- PMOS
- P-doped MOS.
- P-n junction [PN-Übergang]
- Positive logic [Positive Logik]
- Positive logic means that the signals are active high.
- Potentiometer [Potentiometer, Poti]
- Variable resistor the value of which is determined
by the position of a slider or a knob.
- PROM
- Programmable ROM. This memory type can be written once, then it behaves
like a ROM. Series designator: 25xx, where xx is the number
of kbits stored. ***
- Pull-up / pull-down resistor
- On active low inputs, you trigger events by pulling
them to LOW. The default state of such inputs is HIGH, which means you have
to apply e.g. +5V (not necessary for TTL). If you would
do this by simply connecting such a line directly to the supply voltage
line, then pulling this line to LOW (which is achieved by connecting this
line to ground via an (electronic) switch) would result in a SHORTCUT between
+5V and GND, which either - if you are lucky - blows a fuse or even
causes severe damage to your machine/device/whatever. So you do not directly
connect that input line to +5V, but via a socalled pull-up
resistor, which "pulls" the voltage level of the input line
"up" to +5V by being connected
at one end to the +5V supply voltage and at the other end to the input line.
If you now pull that line to LOW, there is no shortcut, but the resistor
between +5V and GND instead.
The other way (pulling a line to LOW) is achieved with a pull-down resistor.
I know that this explanation is not the best, but I couldn't find any
better. Can you?
- RAM
- Random Access Memory. Information can be read and written in any order,
the number of read or write accesses is not limited (except by the RAM's
lifetime :-). RAM comes in different flavors: DRAM,
SRAM, VRAM and many more.
- Rectifier [Gleichrichter]
- Circuitry transforming AC into
DC, usually consisting of 4 diodes
(bridge rectifier). Derives from the ancient word 'rectum fire'.
- Resistance [Widerstand]
- The resistance of a conductor (or an
insulator) is how easily current
can flow through it.
Unit: ohm (capital omega).
- Resistor [Widerstand]
- Electrical element with a defined resistance. It
is used as voltage divider or
current limiter. For small resistors, their value
is not printed on the case, but encoded with color rings.
- RGB
- Red-Green-Blue. These three colors are additively mixed in color
TVs and monitors and so give a picture which ranges from black
over all rainbow colors to white. The number of colors displayed
depends on the technology: TTL or ECL supply digital signals and
thus a limited color resolution, usually 4 bits, which results
in 16 colors; analog signals, however, make the color resolution
practically infinite, the number of colors only depends on the
graphics card's memory and on its RAMDAC.
- RMS [Effektivwert]
- Root Mean Square. The real peak value of an AC voltage, which is
U * square root of 2, abbreviation Vrms.
- ROM
- Read Only Memory. Unlike RAM, this type of electronic
memory can only be read. The ROM's content is determined during the
manufacturing process (mask programming). Derivatives are
PROM, EPROM, EEPROM,
and Flash-EPROM.
- Schmitt trigger [Schmitt-Trigger]
- A logical device that outputs 0 if the input voltage is below a
given treshold voltage and 1 otherwise. Used to cleanup the edges
of digital signals. Often comes with a built-in inverter.
- Semiconductor [Halbleiter]
- Pure semiconductor materials like silicon are insulators. But doping
these materials with a very small amount of e.g. Bor makes them
less insulating and, under certain circumstances, conducting electrical
current. Common semiconductors are diodes
and transistors, which are also etched into the silicon
wafers for ICs.
- SMD
- Surface mounted device. SMD technique means soldering elements
(which have specially designed, very short pins) directly onto
the PCB surface without drilling holes.
- Solder [Lötzinn]
- Solder is made of tin (Sn) and lead (Pb) and contains a rosin core,
which makes the solder flow more easily.
- Soldering iron [Lötkolben]
- A tool for soldering electrical conducting connections.
- SRAM
- Static RAM. As opposed to DRAM, this
type of memory doesn't need a continuous refresh, as the information in it
is stored by flip-flops. An example is the
Color RAM used in the Commodore 64.
- Three-state
- See tristate.
- Thyristor
-
- Totem pole
- A possible output connection of a TTL circuit. A totem pole
consists of two transistors, which are driven
complementary.
Depending on the desired output, only one of the two transistors
is conducting. If two totem pole outputs are connected, a shortcut
occurs if they carry different digital signals (0/1 or 1/0).
Therefore it's forbidden to connect two totem pole outputs
together!
- Transformer [Transformator, Trafo]
- A transformer transforms one AC
voltage into another AC voltage. It consists
of two coils (actually not seperate coils, but windings) with a different
number of turns, where one coil (transformer primary winding) encloses the
other (transformer secondary winding). The current flowing through the
transformer primary (the one where the input voltage is applied) envokes a
magnetical field which in turn induces a voltage in the transformer secondary,
the amount of which is determined by the ratio of the number of turns of the
windings.
If a transformer hums, this is due to resonances which can be eliminated in
many cases by simply spraying plastic spray on it.
Oh, btw: A transformer can have more than one secondary, resulting in
more than one output voltage.
- Transistor
- "Transfer Resistor". Invented in 1948 by John Bardeen and Walter
Houser Brattain. In principle, this element is an electrically
controllable semiconductor resistor. It has three
terminals C(ollector), E(mitter), and B(ase). Basically,
when there is no voltage applied to the base, the transistor acts as an
insulator and blocks current flow between C and E.
It is used both as an amplifier and an electronic switch.
- Triac
- Tristate
- The output lines of tristate circuits can have three states: HIGH, LOW,
and HIGH IMPEDANCE, where the latter is equivalent to not being connected.
- TTL
- Transistor-Transistor-Logic. The TTL family needs a supply voltage
of 4.75V-5.25V, the switching threshold is less than 0.8V for LOW and
greater than 2.4V for HIGH.
Type Meaning typ. tpd* [ns] Power[mW/G]
----------------------------------------------------------------
74xx Standard 10 10
74ALSxx Advanced Low Power Schottky 4 1
74ASxx Advanced Schottky 1.5 20
74Fxx Fast Schottky 2 4
74Hxx High Power 6 20
74Lxx Low Power 30 1
74LSxx Low Power Schottky 9 20
74Sxx Schottky 5 20
* tpd = propagation delay time. Time for an output level
change after the input level changed.
- Vector board [Lochrasterplatine]
- Board made of pertinax or other insulating material
for building prototype circuits. It contains a matrix of holes. There are
also types with soldering pads around the holes, these should be preferred.
- Voltage [Spannung]
- Electrical entity which is the cause for current
flow. When talking about AC voltages, peak-to-peak
voltage means - as the name suggests - the absolute amount of voltage
between the upper and the lower bound; Abbreviation: Vpp.
Unit: Volt (V).
- Voltmeter
- Device for measuring electrical voltage. Usually part
of a multimeter.
- VRAM
- Video RAM. VRAM is dual-ported, so that you can read
and write simultaneously, resulting in a much smaller access time. As the
name suggests, VRAMs are employed as memory on graphic cards.
- XOR
- See EXOR
