The linear-backbone "polymer blacks" (polyacetylene, polypyrrole, and polyaniline) and their copolymers are the main class of conductive polymers. Historically, these are known as Melanins. In 1963 Australians DE Weiss and coworkers reported iodine-doped oxidized polypyrrole blacks with resistivities as low as 1 ohm/cm. Subsequent papers reported resistances as low as 0.03 Ohm/cm. With the notable exception of Charge transfer complexes (some of which are even superconductors), organic molecules had previously been considered insulators or at best weakly conducting semiconductors.
Over a decade later in 1977, Shirakawa, Heeger, and MacDiarmid reported equivalent high conductivity in rather similarly oxidized and iodine-doped polyacetylene. They later received the 2000 Nobel prize in chemistry for " The discovery and development of conductive polymers ".
Sunday, May 16, 2010
Band structure
atoms - crystal - vacuum
In a single H-atom an electron resides in well known orbits. Note that the orbits are called s,p,d in order of increasing circular current.
Putting two atoms together leads to delocalized orbits across two atoms, a so called covalent bond. Due to Paulis principle in every state there is max one electron.
This can be continued with more atoms.
Using 6 carbon atoms one can create molecular orbits which allow for circular current. Filling the states following Pauli's principle leads to zero net current. Current due to uneven filling needs an energy investment.
Proceeding in a regular fashion and create a crystal, which may after creation be cut into a tape and fused together at the ends allow for circular currents.
For this regular solid the band structure can be calculated or measured.
Integrating over the k axis gives the bands of a semiconductor showing a full valence band and an empty conduction band. Generally stopping at the vacuum level is dumb, because some people want to calculate: photoemission, inverse photoemission, Semiconductor_detector#particle_detectors
After the band structure is determined states can be combined to generate wave packets. As this is analogous to wave packages in free space, the results are similar.
An alternative description, which does not really appreciate the strong Coulomb interaction, shoots free electrons into the crystal and looks at the scattering.
A third alternative description uses strongly localized unpaired electrons in chemical bonds, which looks almost like a Mott insulator.
In a single H-atom an electron resides in well known orbits. Note that the orbits are called s,p,d in order of increasing circular current.
Putting two atoms together leads to delocalized orbits across two atoms, a so called covalent bond. Due to Paulis principle in every state there is max one electron.
This can be continued with more atoms.
Using 6 carbon atoms one can create molecular orbits which allow for circular current. Filling the states following Pauli's principle leads to zero net current. Current due to uneven filling needs an energy investment.
Proceeding in a regular fashion and create a crystal, which may after creation be cut into a tape and fused together at the ends allow for circular currents.
For this regular solid the band structure can be calculated or measured.
Integrating over the k axis gives the bands of a semiconductor showing a full valence band and an empty conduction band. Generally stopping at the vacuum level is dumb, because some people want to calculate: photoemission, inverse photoemission, Semiconductor_detector#particle_detectors
After the band structure is determined states can be combined to generate wave packets. As this is analogous to wave packages in free space, the results are similar.
An alternative description, which does not really appreciate the strong Coulomb interaction, shoots free electrons into the crystal and looks at the scattering.
A third alternative description uses strongly localized unpaired electrons in chemical bonds, which looks almost like a Mott insulator.
Semiconductor
A semiconductor is a solid material that has electrical conductivity in between that of a conductor and that of an insulator; it can vary over that wide range either permanently or dynamically.Semiconductors are tremendously important in technology. Semiconductor devices, electronic components made of semiconductor materials, are essential in modern electrical devices. Examples range from computers to cellular phones to digital audio players. Silicon is used to create most semiconductors commercially, but dozens of other materials are used as well.
Semiconductors are very similar to insulators. The two categories of solids differ primarily in that insulators have larger band gaps — energies that electrons must acquire to be free to move from atom to atom. In semiconductors at room temperature, just as in insulators, very few electrons gain enough thermal energy to leap the band gap from the valence band to the conduction band, which is necessary for electrons to be available for electric current conduction. For this reason, pure semiconductors and insulators in the absence of applied electric fields, have roughly similar resistance. The smaller bandgaps of semiconductors, however, allow for other means besides temperature to control their electrical properties.
Semiconductors' intrinsic electrical properties are often permanently modified by introducing impurities by a process known as doping. Usually, it is sufficient to approximate that each impurity atom adds one electron or one "hole" (a concept to be discussed later) that may flow freely. Upon the addition of a sufficiently large proportion of impurity dopants, semiconductors will conduct electricity nearly as well as metals. Depending on the kind of impurity, a doped region of semiconductor can have more electrons or holes, and is named N-type or P-type semiconductor material, respectively. Junctions between regions of N- and P-type semiconductors create electric fields, which cause electrons and holes to be available to move away from them, and this effect is critical to semiconductor device operation. Also, a density difference in the amount of impurities produces a small electric field in the region which is used to accelerate non-equilibrium electrons or holes.
In addition to permanent modification through doping, the resistance of semiconductors is normally modified dynamically by applying electric fields. The ability to control resistance/conductivity in regions of semiconductor material dynamically through the application of electric fields is the feature that makes semiconductors useful. It has led to the development of a broad range of semiconductor devices, like transistors and diodes. Semiconductor devices that have dynamically controllable conductivity, such as transistors, are the building blocks of integrated circuits devices like the microprocessor. These "active" semiconductor devices (transistors) are combined with passive components implemented from semiconductor material such as capacitors and resistors, to produce complete electronic circuits.
In most semiconductors, when electrons lose enough energy to fall from the conduction band to the valence band (the energy levels above and below the band gap), they often emit light. This photoemission process underlies the light-emitting diode (LED) and the semiconductor laser, both of which are very important commercially. Conversely, semiconductor absorption of light in photodetectors excites electrons to move from the valence band to the higher energy conduction band, thus facilitating detection of light and vary with its intensity. This is useful for fiber optic communications, and providing the basis for energy from solar cells.
Semiconductors may be elemental materials such as silicon and germanium, or compound semiconductors such as gallium arsenide and indium phosphide, or alloys such as silicon germanium or aluminium gallium arsenide.
Semiconductors are very similar to insulators. The two categories of solids differ primarily in that insulators have larger band gaps — energies that electrons must acquire to be free to move from atom to atom. In semiconductors at room temperature, just as in insulators, very few electrons gain enough thermal energy to leap the band gap from the valence band to the conduction band, which is necessary for electrons to be available for electric current conduction. For this reason, pure semiconductors and insulators in the absence of applied electric fields, have roughly similar resistance. The smaller bandgaps of semiconductors, however, allow for other means besides temperature to control their electrical properties.
Semiconductors' intrinsic electrical properties are often permanently modified by introducing impurities by a process known as doping. Usually, it is sufficient to approximate that each impurity atom adds one electron or one "hole" (a concept to be discussed later) that may flow freely. Upon the addition of a sufficiently large proportion of impurity dopants, semiconductors will conduct electricity nearly as well as metals. Depending on the kind of impurity, a doped region of semiconductor can have more electrons or holes, and is named N-type or P-type semiconductor material, respectively. Junctions between regions of N- and P-type semiconductors create electric fields, which cause electrons and holes to be available to move away from them, and this effect is critical to semiconductor device operation. Also, a density difference in the amount of impurities produces a small electric field in the region which is used to accelerate non-equilibrium electrons or holes.
In addition to permanent modification through doping, the resistance of semiconductors is normally modified dynamically by applying electric fields. The ability to control resistance/conductivity in regions of semiconductor material dynamically through the application of electric fields is the feature that makes semiconductors useful. It has led to the development of a broad range of semiconductor devices, like transistors and diodes. Semiconductor devices that have dynamically controllable conductivity, such as transistors, are the building blocks of integrated circuits devices like the microprocessor. These "active" semiconductor devices (transistors) are combined with passive components implemented from semiconductor material such as capacitors and resistors, to produce complete electronic circuits.
In most semiconductors, when electrons lose enough energy to fall from the conduction band to the valence band (the energy levels above and below the band gap), they often emit light. This photoemission process underlies the light-emitting diode (LED) and the semiconductor laser, both of which are very important commercially. Conversely, semiconductor absorption of light in photodetectors excites electrons to move from the valence band to the higher energy conduction band, thus facilitating detection of light and vary with its intensity. This is useful for fiber optic communications, and providing the basis for energy from solar cells.
Semiconductors may be elemental materials such as silicon and germanium, or compound semiconductors such as gallium arsenide and indium phosphide, or alloys such as silicon germanium or aluminium gallium arsenide.
Charge transfer complexes
The first highly-conductive organic compounds were the Charge transfer complexes. In 1954, researchers at Bell Labs and elsewhere reported Charge transfer complexes with resistivities as low as 8 ohms-cm . In the early 1970's, salts of tetrathiafulvalene were shown to exhibit almost metallic conductivity, while superconductivity was demonstrated in 1980. Broad research on charge transfer salts continues today.
Charge Transfer (CT) bands in transition metal complexes result from movement of electrons between molecular orbitals (MO) that are predominantly metal in character and those that are predominantly ligand in character. If the electron moves from the MO with ligand like character to the metal like one, the complexes is called Ligand to Metal Charge Transfer (LMCT) complex. If the electron moves from the MO with metal like character to the ligand like one, the complexes is called Metal to Ligand Charge Transfer (MLCT) complex. Thus a MLCT results in oxidation of the metal center whereas a LMCT results in the reduction of the metal center. Resonance Raman Spectroscopy is a powerful technique to assign and characterize charge transfer bands.
Charge Transfer (CT) bands in transition metal complexes result from movement of electrons between molecular orbitals (MO) that are predominantly metal in character and those that are predominantly ligand in character. If the electron moves from the MO with ligand like character to the metal like one, the complexes is called Ligand to Metal Charge Transfer (LMCT) complex. If the electron moves from the MO with metal like character to the ligand like one, the complexes is called Metal to Ligand Charge Transfer (MLCT) complex. Thus a MLCT results in oxidation of the metal center whereas a LMCT results in the reduction of the metal center. Resonance Raman Spectroscopy is a powerful technique to assign and characterize charge transfer bands.
Field-effect transistor
The field-effect transistor (FET) is a type of transistor that relies on an electric field to control the shape and hence the conductivity of a 'channel' in a semiconductor material. The concept of the field effect transistor predates the bipolar junction transistor (BJT), though it was not physically implemented until after BJTs, due to the limitations of semiconductor materials and relative ease of manufacturing BJTs compared to FETs at the time.
Terminals
All FETs except J-FETs have four terminals, which are known as the gate, drain, source and body/base/bulk/substrate. Compare these to the terms used for BJTs: base, collector and emitter. BJTs and J-FETs have no body terminal.
The names of the terminals refer to their functions. The gate terminal may be thought of as controlling the opening and closing of a physical gate. This gate permits electrons to flow through or blocks their passage by creating or eliminating a channel between the source and drain. Electrons flow from the source terminal towards the drain terminal if influenced by an applied voltage. The body simply refers to the bulk of the semiconductor in which the gate, source and drain lie. Usually the body terminal is connected to the highest or lowest voltage within the circuit, depending on type. The body terminal and the source terminal are sometimes connected together since the source is also sometimes connected to the highest or lowest voltage within the circuit, however there are several uses of FETs which do not have such a configuration, such as transmission gates and cascode circuits.
Terminals
All FETs except J-FETs have four terminals, which are known as the gate, drain, source and body/base/bulk/substrate. Compare these to the terms used for BJTs: base, collector and emitter. BJTs and J-FETs have no body terminal.
The names of the terminals refer to their functions. The gate terminal may be thought of as controlling the opening and closing of a physical gate. This gate permits electrons to flow through or blocks their passage by creating or eliminating a channel between the source and drain. Electrons flow from the source terminal towards the drain terminal if influenced by an applied voltage. The body simply refers to the bulk of the semiconductor in which the gate, source and drain lie. Usually the body terminal is connected to the highest or lowest voltage within the circuit, depending on type. The body terminal and the source terminal are sometimes connected together since the source is also sometimes connected to the highest or lowest voltage within the circuit, however there are several uses of FETs which do not have such a configuration, such as transmission gates and cascode circuits.
Quantum realm
Quantum realm is a term of art in physics referring to scales where quantum mechanical effects become important . Typically, this means distances of 100 nanometers (nm) or less. Not coincidentally, this is the same scale as Nanotechnology.
While originating on the nanometer scale, such effects can operate on a macro level. The classic example is Electron tunneling. Most fundamental processes in Molecular electronics, Organic electronics, and Organic semiconductors also originate in the quantum realm.
The quantum realm can also sometimes paradoxically involve actions at long distances. E.g., "The quantum realm involves curious correlations between distant events. A well-known example is David Bohm's (1951) version of the famous thought experiment that Einstein, Podolsky and Rosen proposed in 1935 (henceforth, the EPR/B experiment). Pairs of particles are emitted from a source in the so-called spin singlet state and rush in opposite directions . When the particles are widely separated from each other, they each encounter a measuring apparatus that can be set to measure their spin components along various directions. Although the measurement events are distant from each other, so that no slower-than-light or light signal can travel between them, the measurement outcomes are curiously correlated
While originating on the nanometer scale, such effects can operate on a macro level. The classic example is Electron tunneling. Most fundamental processes in Molecular electronics, Organic electronics, and Organic semiconductors also originate in the quantum realm.
The quantum realm can also sometimes paradoxically involve actions at long distances. E.g., "The quantum realm involves curious correlations between distant events. A well-known example is David Bohm's (1951) version of the famous thought experiment that Einstein, Podolsky and Rosen proposed in 1935 (henceforth, the EPR/B experiment). Pairs of particles are emitted from a source in the so-called spin singlet state and rush in opposite directions . When the particles are widely separated from each other, they each encounter a measuring apparatus that can be set to measure their spin components along various directions. Although the measurement events are distant from each other, so that no slower-than-light or light signal can travel between them, the measurement outcomes are curiously correlated
Organic electronic devices
A 1972 paper in the journal Science proposed a model for electronic conduction in the melanins. Historically, melanin is another name for the various oxidized polyacetylene, polyaniline, and Polypyrrole "blacks" and their mixed copolymers, all commonly-used in present day organic electronic devices. E.g., some fungal melanins are pure polyacetylene. This model drew upon the theories of Neville Mott and others on conduction in disordered materials. Subsequently, in 1974, the same workers at the Physics Department of The University of Texas M. D. Anderson Cancer Center reported an organic electronic device, a voltage-controlled switch
Their material also incidentally demonstrated "negative differential resistance", now a hall-mark of such materials. A contemporary news article in the journal Nature noted this materials "strikingly high conductivity'. These researchers further patented batteries, etc. using organic semiconductive materials. Their original "gadget" is now in the Smithsonian's collection of early electronic devices.
This work, like that the decade-earlier report of high-conductivity in a polypyrrole, was "too early" and went unrecognized outside of pigment cell research until recently. At the time, few except cancer research institutes were interested in the electronic properties of such polymers, which are applicable to the treatment of melanoma.
Their material also incidentally demonstrated "negative differential resistance", now a hall-mark of such materials. A contemporary news article in the journal Nature noted this materials "strikingly high conductivity'. These researchers further patented batteries, etc. using organic semiconductive materials. Their original "gadget" is now in the Smithsonian's collection of early electronic devices.
This work, like that the decade-earlier report of high-conductivity in a polypyrrole, was "too early" and went unrecognized outside of pigment cell research until recently. At the time, few except cancer research institutes were interested in the electronic properties of such polymers, which are applicable to the treatment of melanoma.
Organic electronics
Organic electronics, or plastic electronics, is a branch of electronics that deals with conductive polymers, plastics, or small molecules. It is called 'organic' electronics because the polymers and small molecules are carbon-based, like the molecules of living things. This is as opposed to traditional electronics which relies on inorganic conductors such as copper or silicon.
In addition to organic Charge transfer complexes, technically, electrically conductive polymers are mainly derivatives of polyacetylene black (the "simplest melanin"). Examples include PA (more specificially iodine-doped trans-polyacetylene); polyaniline: PANI, when doped with a protonic acid; and poly(dioctyl-bithiophene): PDOT.
For a history of the field, see "An Overview of the First Half-Century of Molecular Electronics" by Noel S. Hush, Ann. N.Y. Acad. Sci. 1006: 1–20 (2003).
The men principally credited for the discovery and development of highly-conductive organic polymers (at least of the rigid-backbone "polyacetylene" class) are Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa, who were jointly awarded the Nobel Prize in Chemistry in 2000 for the 1977 discovery and development of oxidized, iodine-doped polyacetylene.
Interestingly, this prize passed over the much earlier discovery of highly-conductive organic Charge transfer complexes, some of which are even superconductive. Similarly, the first demonstration of high-conductivity in the linear backbone polymers was a series of papers by Weiss et al in 1963. These workers reported a conductivity of 1 S/cm in a similarly iodine-"doped" and oxidized polypyrrole black.
Conduction mechanisms in such materials involve resonance stabilization and delocalization of pi electrons along entire polymer backbones, as well as mobility gaps, tunneling, and phonon-assisted hopping.
Melanin voltage-controlled switch, an "active" organic polymer electronic device from 1974. Now in the Smithsonian.
Conductive polymers are lighter, more flexible, and less expensive than inorganic conductors. This makes them a desirable alternative in many applications. It also creates the possibility of new applications that would be impossible using copper or silicon.
New applications include smart windows and electronic paper. Conductive polymers are expected to play an important role in the emerging science of molecular computers.
In general organic conductive polymers have a higher resistance and therefore conduct electricity poorly and inefficiently, as compared to inorganic conductors. Researchers currently are exploring ways of "doping" organic semiconductors, like melanin, with relatively small amounts of conductive metals to boost conductivity. However, for many applications, inorganic conductors will remain the only viable option.
In addition to organic Charge transfer complexes, technically, electrically conductive polymers are mainly derivatives of polyacetylene black (the "simplest melanin"). Examples include PA (more specificially iodine-doped trans-polyacetylene); polyaniline: PANI, when doped with a protonic acid; and poly(dioctyl-bithiophene): PDOT.
For a history of the field, see "An Overview of the First Half-Century of Molecular Electronics" by Noel S. Hush, Ann. N.Y. Acad. Sci. 1006: 1–20 (2003).
The men principally credited for the discovery and development of highly-conductive organic polymers (at least of the rigid-backbone "polyacetylene" class) are Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa, who were jointly awarded the Nobel Prize in Chemistry in 2000 for the 1977 discovery and development of oxidized, iodine-doped polyacetylene.
Interestingly, this prize passed over the much earlier discovery of highly-conductive organic Charge transfer complexes, some of which are even superconductive. Similarly, the first demonstration of high-conductivity in the linear backbone polymers was a series of papers by Weiss et al in 1963. These workers reported a conductivity of 1 S/cm in a similarly iodine-"doped" and oxidized polypyrrole black.
Conduction mechanisms in such materials involve resonance stabilization and delocalization of pi electrons along entire polymer backbones, as well as mobility gaps, tunneling, and phonon-assisted hopping.
Melanin voltage-controlled switch, an "active" organic polymer electronic device from 1974. Now in the Smithsonian.
Conductive polymers are lighter, more flexible, and less expensive than inorganic conductors. This makes them a desirable alternative in many applications. It also creates the possibility of new applications that would be impossible using copper or silicon.
New applications include smart windows and electronic paper. Conductive polymers are expected to play an important role in the emerging science of molecular computers.
In general organic conductive polymers have a higher resistance and therefore conduct electricity poorly and inefficiently, as compared to inorganic conductors. Researchers currently are exploring ways of "doping" organic semiconductors, like melanin, with relatively small amounts of conductive metals to boost conductivity. However, for many applications, inorganic conductors will remain the only viable option.
Rectifier
A rectifier is an electrical device that converts alternating current to direct current, a process known as rectification. Rectifiers are used as components of power supplies and as detectors of radio signals. Rectifiers may be made of solid state diodes, vacuum tube diodes, mercury arc valves, and other components.
A circuit which performs the opposite function (converting DC to AC) is known as an inverter.
When only one diode is used to rectify AC (by blocking the negative or positive portion of the waveform), the difference between the term diode and the term rectifier is merely one of usage, i.e., the term rectifier describes a diode that is being used to convert AC to DC. Almost all rectifiers comprise a number of diodes in a specific arrangement for more efficiently converting AC to DC than is possible with only one diode. Before the development of silicon semiconductor rectifiers, vacuum tube diodes and copper(I) oxide or selenium rectifier stacks were used.
Early radio receivers, called crystal radios, used a "cat's whisker" of fine wire pressing on a crystal of galena (lead sulfide) to serve as a point-contact rectifier or "crystal detector". In gas heating systems flame rectification can be used to detect a flame. Two metal electrodes in the outer layer of the flame provide a current path and rectification of an applied alternating voltage, but only while the flame is pr
A circuit which performs the opposite function (converting DC to AC) is known as an inverter.
When only one diode is used to rectify AC (by blocking the negative or positive portion of the waveform), the difference between the term diode and the term rectifier is merely one of usage, i.e., the term rectifier describes a diode that is being used to convert AC to DC. Almost all rectifiers comprise a number of diodes in a specific arrangement for more efficiently converting AC to DC than is possible with only one diode. Before the development of silicon semiconductor rectifiers, vacuum tube diodes and copper(I) oxide or selenium rectifier stacks were used.
Early radio receivers, called crystal radios, used a "cat's whisker" of fine wire pressing on a crystal of galena (lead sulfide) to serve as a point-contact rectifier or "crystal detector". In gas heating systems flame rectification can be used to detect a flame. Two metal electrodes in the outer layer of the flame provide a current path and rectification of an applied alternating voltage, but only while the flame is pr
Stereoelectronics
Stereoelectronics is the study of the interplay between the electronic structure and geometry of a molecule. For example, in the case of reactant molecules with chiral isomers the electron distribution can determine the stereochemistry of the reactions of the different diastereomers
History, origins, and generations
In April 1949, the German engineer Werner Jacobi (Siemens AG) filed the earliest patent for an integrated-circuit-like semiconductor amplifying device showing five transistors on a common substrate arranged in a 3-stage amplifier arrangement. Jacobi discloses small and cheap hearing aids as typical industrial applications of his patent. A commercial use of his patent has not been reported.
The integrated circuit was later also conceived by a radar scientist, Geoffrey W.A. Dummer (1909-2002), working for the Royal Radar Establishment of the British Ministry of Defence, and published in Washington, D.C. on May 7, 1952. Dummer unsuccessfully attempted to build such a circuit in 1956.
A precursor idea to the IC was to create small ceramic squares (wafers), each one containing a single miniaturized component. Components could then be integrated and wired into a bidimensional or tridimensional compact grid. This idea, which looked very promising in 1957, was proposed to the US Army by Jack Kilby, and led to the short-lived Micromodule Program (similar to 1951's Project Tinkertoy). However, as the project was gaining momentum, Kilby came up with a new, revolutionary design: the IC.
The first integrated circuits were manufactured independently by two scientists: Jack Kilby of Texas Instruments filed a patent for a "Solid Circuit" made of germanium on February 6, 1959. Kilby received several US patents. Robert Noyce of Fairchild Semiconductor was awarded a patent for a more complex "unitary circuit" made of Silicon on April 25, 1961. ( the Chip that Jack built for more information.)
Noyce credited Kurt Lehovec of Sprague Electric for the principle of p-n junction isolation caused by the action of a biased p-n junction (the diode) as a key concept behind the IC.
The integrated circuit was later also conceived by a radar scientist, Geoffrey W.A. Dummer (1909-2002), working for the Royal Radar Establishment of the British Ministry of Defence, and published in Washington, D.C. on May 7, 1952. Dummer unsuccessfully attempted to build such a circuit in 1956.
A precursor idea to the IC was to create small ceramic squares (wafers), each one containing a single miniaturized component. Components could then be integrated and wired into a bidimensional or tridimensional compact grid. This idea, which looked very promising in 1957, was proposed to the US Army by Jack Kilby, and led to the short-lived Micromodule Program (similar to 1951's Project Tinkertoy). However, as the project was gaining momentum, Kilby came up with a new, revolutionary design: the IC.
The first integrated circuits were manufactured independently by two scientists: Jack Kilby of Texas Instruments filed a patent for a "Solid Circuit" made of germanium on February 6, 1959. Kilby received several US patents. Robert Noyce of Fairchild Semiconductor was awarded a patent for a more complex "unitary circuit" made of Silicon on April 25, 1961. ( the Chip that Jack built for more information.)
Noyce credited Kurt Lehovec of Sprague Electric for the principle of p-n junction isolation caused by the action of a biased p-n junction (the diode) as a key concept behind the IC.
Integrated circuit
In electronics, an integrated circuit (also known as IC, microcircuit, microchip, silicon chip, or chip) is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) that has been manufactured in the surface of a thin substrate of semiconductor material.
A hybrid integrated circuit is a miniaturized electronic circuit constructed of individual semiconductor devices, as well as passive components, bonded to a substrate or circuit board
Integrated circuits were made possible by experimental discoveries which showed that semiconductor devices could perform the functions of vacuum tubes, and by mid-20th-century technology advancements in semiconductor device fabrication. The integration of large numbers of tiny transistors into a small chip was an enormous improvement over the manual assembly of circuits using discrete electronic components. The integrated circuit's mass production capability, reliability, and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors.
There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography and not constructed one transistor at a time. Performance is high since the components switch quickly and consume little power, because the components are small and close together. As of 2006, chip areas range from a few square mm to around 350 mm², with up to 1 million transistors per mm².
A hybrid integrated circuit is a miniaturized electronic circuit constructed of individual semiconductor devices, as well as passive components, bonded to a substrate or circuit board
Integrated circuits were made possible by experimental discoveries which showed that semiconductor devices could perform the functions of vacuum tubes, and by mid-20th-century technology advancements in semiconductor device fabrication. The integration of large numbers of tiny transistors into a small chip was an enormous improvement over the manual assembly of circuits using discrete electronic components. The integrated circuit's mass production capability, reliability, and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors.
There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography and not constructed one transistor at a time. Performance is high since the components switch quickly and consume little power, because the components are small and close together. As of 2006, chip areas range from a few square mm to around 350 mm², with up to 1 million transistors per mm².
Integrated circuit
In electronics, an integrated circuit (also known as IC, microcircuit, microchip, silicon chip, or chip) is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) that has been manufactured in the surface of a thin substrate of semiconductor material.
A hybrid integrated circuit is a miniaturized electronic circuit constructed of individual semiconductor devices, as well as passive components, bonded to a substrate or circuit board
Integrated circuits were made possible by experimental discoveries which showed that semiconductor devices could perform the functions of vacuum tubes, and by mid-20th-century technology advancements in semiconductor device fabrication. The integration of large numbers of tiny transistors into a small chip was an enormous improvement over the manual assembly of circuits using discrete electronic components. The integrated circuit's mass production capability, reliability, and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors.
There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography and not constructed one transistor at a time. Performance is high since the components switch quickly and consume little power, because the components are small and close together. As of 2006, chip areas range from a few square mm to around 350 mm², with up to 1 million transistors per mm².
A hybrid integrated circuit is a miniaturized electronic circuit constructed of individual semiconductor devices, as well as passive components, bonded to a substrate or circuit board
Integrated circuits were made possible by experimental discoveries which showed that semiconductor devices could perform the functions of vacuum tubes, and by mid-20th-century technology advancements in semiconductor device fabrication. The integration of large numbers of tiny transistors into a small chip was an enormous improvement over the manual assembly of circuits using discrete electronic components. The integrated circuit's mass production capability, reliability, and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors.
There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography and not constructed one transistor at a time. Performance is high since the components switch quickly and consume little power, because the components are small and close together. As of 2006, chip areas range from a few square mm to around 350 mm², with up to 1 million transistors per mm².
Home > Nation > Top Stories Napocor, Meralco take ‘war’ to newspaper ads
MANILA, Philippines - The "blame game" between Manila Electric Co. (Meralco) and the National Power Corp. (Napocor) on high power rates shifted Tuesday from the Senate to national newspapers.Full-page ads appeared in major newspapers - some blaming Napocor, others blaming Meralco for high electricity rates. Noticeably, "pro-Meralco" groups placed more full-page ads in some newspapers."Hoy Gising (Hey wake up)!" was the theme of the latest "pro-Meralco" ads, which said systems loss allowances are "normal, usual and standard."One of the pro-Meralco ads noted that Meralco under the Lopez Group had brought down systems losses to 9.65 percent in 2007. "Meralco has reduced system loss to its lowest level in 27 years," it said.This was a far cry from the 21 percent systems losses incurred by Meralco when it was being run by "Marcos cronies" during Martial Law, the ad stated.It said that when the Lopez Group took over Meralco in 1987, the systems losses went down to 17 percent in 1988 at to 15 percent in 1989. On the other hand, the ad stated that a law in 1994 limited maximum deductible systems loss to 9.5 percent in urban areas and 14 percent for rural areas.Another pro-Meralco ad which appeared in another newspaper claimed that Meralco fees actually went down in the last five years.Yet another ad questioned Napocor for its P9 per kilowatthour generation cost at the Wholesale Electricity Spot Market (WESM). "May bukol ba ang presyo ng Napocor electricity (Is there a profit to be made from Napocor electricity)?" it asked. On the other hand, pro-Napocor ads placed by the "National Labor Union" also appeared in newspapers citing discrepancies between Meralco's ads and figures on its website.It also questioned Meralco's "sweetheart deals" with power generating firms owned by the Lopez Group."Mas binibigyan ng prayoridad ng Meralco ang Sta. Rita at San Lorenzo. Mas inuna ang mga sweetheart deals ng Meralco sa kanyang affiliate companies (Meralco is prioritizing Sta. Rita and San Lorenzo. It puts sweetheart deals first because of its affiliate companies)," it said.The ad said Sta. Rita and San Lorenzo are owned by First Gen Corp., which in turn is controlled (66.23 percent) by First Philippines Holding Corp. First Philippine Holdings Corp. also controls Meralco with a 33.4 percent stake.First Philippine Holdings Corp., is in turn is controlled by Benpres Holdings Corp. (43.2 percent) - whose 55.4 percent stake is owned by the Lopez family."The issues being raised go beyond power rates. The Napocor is in a better position to explain its power rate structure," it said. It also said shareholders of Meralco outside of the Lopezes want to keep Meralco profitable to get a good return from their investments, "but these same shareholders want to be assured that Meralco's profit are earned with honor.""Shareholders not within the ambit of the Lopezes' power want to stop Meralco management's double talk. Only by being transparent can all of us, stakehoholders and consumers, be assured that we are being charged fair and equitable power rates... Protect the public, lower electriccost," it added. -
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