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Topic: Virtual ground

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Electronic amplifier

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Operational amplifier

Current mirror

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	Encyclopedia topic: Virtual ground (Site not responding. Last check: 2007-10-22)
		Virtual ground is a concept found in electrical circuit (An electrical device that provides a path for electrical current to flow) designs.
		It identifies a point in an electric circuit as being held close to the ground ((art) the surface (as a wall or canvas) prepared to take the paint for a painting) level electric potential (The difference in electrical charge between two points in a circuit expressed in volts).
		A typical example for a virtual ground point is found in circuits using operational amplifier (additional info and facts about operational amplifier) s with negative feedback.
	www.absoluteastronomy.com /encyclopedia/v/vi/virtual_ground.htm (146 words)

	Virtual ground - Wikipedia, the free encyclopedia
		Virtual ground (sometimes called virtual earth) is a very important concept found in electronic circuit designs.
		A virtual ground presents a very low impedance to any signal connected to it and it therefore provides the perfect type of input for current type signal sources.
		In an inverting amplifier configuration with the + input grounded, the inverting (-)input is said to be a virtual ground.
	en.wikipedia.org /wiki/Virtual_ground (423 words)

	Ground (electricity) - Wikipedia, the free encyclopedia
		In a mains (AC power) wiring installation, the grounding is the wire that carries currents away under fault conditions.
		This grounding wire is usually but not always connected to the neutral wire at some point and they may even share a cable for part of the system under some conditions.
		During dry weather, the ground connection often developed a high resistance, requiring water to be poured on the ground rod to enable the telegraph to work or phones to ring.
	en.wikipedia.org /wiki/Ground_(electricity) (805 words)

	Virtual Economy Home Page
		At the heart of the Virtual Economy are sophisticated computer models which are very similar to those the Chancellor and his advisers use to prepare the Budget and to keep the economy on track.
		Ground floor (this floor) - Chancellor's office with an introduction to the Virtual Economy and an information bureau with teachers' guides, student guides and details of the model.
		There are further details available of the development of the Virtual Economy and the groups involved in its preparation.
	www.bized.ac.uk /virtual/economy (347 words)

	Virtual ground MOS EPROM or ROM matrix - Patent 4281397
		An array of rows and columns of memory cells of the virtual ground type employs a cell layout which has one column line per column instead of requiring extra lines for ground.
		In accordance with one embodiment of the invention, an array of rows and columns of memory cells of the virtual ground type employs a cell layout which has one column line per column instead of requiring extra lines for ground.
		The transistor 27a must be large enough to pull down the load device 26a, conduct to ground any current through transistors 10a and 10c and maintain a very low level of approximately 0.2 to 0.3 volts on the node 12a.
	www.freepatentsonline.com /4281397.html (3628 words)

	Single Supply Op Amp Design
		The virtual ground is simply a voltage reference that is typically half way between Vcc and ground.
		An easier way to do this is to use a virtual ground circuit, such as the TLE2426 virtual ground (the "Rail Splitter") from Texas Instruments.
		The virtual ground can now be used just like a normal ground in your circuit, but you have to remember that the virtual ground has limited output current.
	www.swarthmore.edu /NatSci/echeeve1/Ref/SingleSupply/SingleSupply.html (573 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		It is yet another object of the present invention to provide a circuit which alters the magnitude of the current flowing into a virtual ground terminal of the circuit without altering the phase of the current.
		In accordance with the present invention, a method of enhancing the performance of a circuit having a virtual ground terminal with a current flowing into the virtual ground terminal with a phase value is disclosed.
		The grounded tee configuration of capacitors C7, C8 and C9 is an important aspect of the present invention.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=99/50958.991007&ELEMENT_SET=DECL (3385 words)

	Virtual Ground Circuits
		The input and output are both referenced to the same ground point, so nobody cares that the virtual ground isn't precisely centered between the rails.
		It is, however, the least accurate of the buffered virtual ground circuits.
		In a headphone amp, the circuit has several resistors and such going to ground, but virtually all of the dynamic current to ground is the return current from the headphones.
	tangentsoft.net /elec/vgrounds.html (2773 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		As C7 is connected to the virtual ground connection of the operational amplifier A2 and C9 is connected to circuit ground through the switch S5, capacitors C9 and C7 combine in parallel and the value of Cf is increased.
		However, because the capacitor tee structure results in a current division with only a portion of the total feedback current flowing into the virtual ground terminal of the operational amplifier, the effective value of the feedback capacitance, Cf, is not equal to Cf when the second switch S5 is closed.
		The grounded tee configuration of capacitors C7, CS and C9 is an important aspect of the present invention.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=99/50959.991007&ELEMENT_SET=DECL (3534 words)

	Chapter IV S. Ground Vehicles
		Ground vehicle platforms require targeting, location, and acquisition systems capable of rapid detection, recognition, identification, handoff, or engagement of both ground and aerial targets beyond the threat’s detection range.
		Ground vehicle platforms must possess the capability to execute at an improved maneuver tempo as a result of digitizing the battlefield.
		Virtual concepts and designs will mirror technology and can be readily evaluated for mobility, agility, survivability, lethality, and transportability, forming the basis for validation, verification, and accreditation.
	www.fas.org /man/dod-101/army/docs/astmp98/sec4s.htm (2342 words)

	VIRTUAL GROUND MONOPOLE HF ANTENNA © 2003 Francesco Errante - www.Radiondistics.com
		VIRTUAL GROUND ¼ of wavelength MONOPOLE (HF) ANTENNA
		("virtual ground" is defined as a point in an electrical circuit that appears to be at ground, but is not actually attached to ground, it is therefore, a node having a 0 degree phase angle difference with respect to ground and has the same electrical potential as the Earth")
		The solution to that problem is given by the possibility of generating the virtual ground node by recombining two radio-electric signals, identical but 180 degree out of phase between them-selves.
	www.esmartstart.com /_framed/250x/radiondistics/antenna_errante.htm (703 words)

	HeadWize: DIY Workshop > Virtual Ground
		The center tap is the ground, the outer transformer lugs
		Virtual ground circuits fix this problem because they always split the battery pack evenly.
		I am planning to build a cmoy altoids tin amp for my Iriver to use with my new Allesandro MS1's and im debating if I should go with the powersupply that is shown in the schematic or build myself a buf643 buffered powersupply.
	www.headwize.com /ubb/showpage.php?fnum=3&tid=5117 (779 words)

	NDM Article - Army Tests Move to ‘Virtual Proving Ground’
		The virtual proving ground is a composite of facilities and technologies throughout the DTC that enhance test programs with the aid of computer modeling and realistic simulations.
		Cozby said DTC’s test centers are striving to integrate their virtual test capabilities into a single virtual proving ground, making it possible to bring these diverse modeling and simulation capabilities to bear on a system under test, as needed.
		Output from a simulated environment is employed to support live and virtual tests of materials to be acquired for chemical and biological protection.
	www.nationaldefensemagazine.org /issues/2001/Nov/Army_Tests.htm (1772 words)

	Virtual Ground Truth (Site not responding. Last check: 2007-10-22)
		It is therefore important for students to understand the mechanisms and problems associated with using satellite imagery and data as well as to build an awareness of the environmental issues to which this source of information can be applied.
		It was used to visualize the region from a remote perspective, to help plan collection of ‘ground’ truth data, to generate an optimal data collection route across the terrain that was followed in the field using GPS.
		Finally after collecting ground truth data the software was used to compare student maps with pre-classified data and to validate data collected by different student groups.
	www.geog.le.ac.uk /RSS-2000/abstracts/049.htm (279 words)

	VIRTUAL GROUND MONOPOLE HF ANTENNA © 2003 Francesco Errante - www.Radiondistics.com
		The balun described hereby enables to demonstrate that once a virtual ground node is available, it is possible to receive and transmit radio-electric signals through the space by employing a single radiating/captating element of a physical length equal to ¼ of a wavelength, without the need for a natural nor an artificial ground plane.
		The balun described hereby enables to demonstrate that each of the two branches of an ½ wavelength open dipole antenna, exhibits a phase-angle difference of +/- 90 degree with respect to the virtual ground node.
		The virtual ground is then made available to the whole of the network by a short electrical connection(6) to the device chassis(7).
	www.esmartstart.com /_framed/250x/radiondistics/suppressor.htm (454 words)

	Mount Washington Observatory: Glossary of Weather Terms (Site not responding. Last check: 2007-10-22)
		- The virtual temperature of a moist air sample is the temperature of dry air which has the same density as the moist air for a given pressure.
		The virtual temperature and the actual temperature are equivalent if no water vapor is in the air.
		Otherwise, the virtual temperature is always higher than the actual temperature because air is less dense for warmer air or for air with more water vapor in it.
	www.mountwashington.org /glossary/glosu-z.html (1107 words)

	Circuit engineering - Virtual ground concept of OPAMP (Site not responding. Last check: 2007-10-22)
		Therefore if there is a voltage applied to any one input while the other is connected to ground, it follows that there is a VIRTUAL GROUND at the other input [since the differential voltage between - and + input must be zero ie., absolute value of -ve input minus absolute value of +ve input].
		The virtual groung is used to determine the direction of current flow through the feedback and input resistors [If=Ii], given that the input impedance of the ideal op.
		A situation in which virtual ground is not used is when a voltage is applied to both inputs, hence no input is grounded.
	www.eng-tips.com /viewthread.cfm?qid=1632 (727 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		The current flowing from VS to virtual ground is VS/RS, in the direction shown by the arrow.
		Virtual ground is maintained by a negative feedback mechanism.
		The 7524 (Analog Devices) is a low-cost 8-bit multiplying DAC which uses CMOS analog switches to flip between VREF and a ground rail; the 7524 requires an op amp at its output to convert current to voltage; it has a latch on the 8-bit input.
	www.engin.brown.edu /courses/en123/Lectures/DAconv.htm (7124 words)

	Modifying CD player DAC circuits (Site not responding. Last check: 2007-10-22)
		If the virtual ground's DC voltage drifts much from the ground the DAC is using for analog ground, distortion would occur for DACs of the style shown in Fig 2.
		Perhaps an op-amp (?!) that measures the low passed filtered difference between real analog ground and virtual ground could be used to issue a correction DC voltage to bias the first triode's grid.
		Maybe a megohm resistor from virtual ground to the inverting op-amp input, and a 1uF cap to analog ground.
	pw2.netcom.com /~wa2ise/radios/tubedac.htm (4795 words)

	Potentiostats - Active I/E Converters
		This ground is often connected to Earth Ground.
		Both the measured current signal and the measured voltage signal are referenced to the potentiostat's ground.
		Whenever the current measurement circuit is overloaded the working electrode is no longer maintained at virtual ground.
	www.consultrsr.com /resources/pstats/design.htm (308 words)

	The Virtual Proving Ground (Site not responding. Last check: 2007-10-22)
		DTC continues to explore further advances with the emergence of synthetic environments, virtual prototypes, and distributed interactive simulation.
		The Virtual Battlefield Environment is a hardware-in-the-loop simulator at the U.S. Army White Sands Missile Range/Electronic Proving Ground, Fort Huachuca, AZ, that challenges communications electronics systems by subjecting them to an accurate simulation of the battlefield radio-frequency electromagnetic environment.
		The Virtual Range System at the U.S. Army Yuma Proving Ground, Yuma, AZ, generates a 3D visualization of any terrain in the world, using Defense Mapping Agency Digital Terrain Elevation Data.
	www.dtc.army.mil /capabilities/vpg.html (594 words)

	VGS - Virtual Ground School - News (Site not responding. Last check: 2007-10-22)
		Our new Virtual Airline Driectory has been up for a few weeks now and we have had a great response from users and the virtual airliens themselves.
		We are pleased to announce the new Virtual Ground School chat room.
		We offer an excellent ground school from which to study from and tests to check the level of knowledge retained from each chapter.
	www.virtualgroundschool.com (452 words)

	Ming the Mechanic: Virtual Futurists
		And now this is the first one in virtual space, in the Second Life virtual world.
		I basically scanned over the world map, which is huge, until I found a suitably large group of people that I could teleport to.
		Rather, we have academics and professionals who dedicate quite some effort to making virtual worlds more viable for various kinds of activities, and who study the dynamics of what happen there.
	ming.tv /flemming2.php/__show_article/_a000010-001540.htm (488 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		INTRODUCTION A solution ground in pH sensor is a conductor in contact with the test solution and connected to the circuit common of the instrument.
		The purpose of a solution ground is not to ground the solution, but to supply an extra electrode for the pH sensor diagnostics.
		It is clear that when the conductivity sensor is in the test solution with the pH sensor, a ground loop is formed from terminal C (the outer electrode of the conductivity sensor) through the test solution and the reference junction Rj to the internal solution ground SG.
	www.emersonprocess.com /raihome/documents/RAI_Liq_WP_Virtual_Solution_Ground_in_pH_Measurement.doc (2545 words)

	New Scientist SPACE - Breaking News - Satellite to have virtual global ground station
		Students will use two ground stations in Denmark and Norway to monitor and control the spacecraft, but they are hoping the onboard radio transponder will also play a role.
		They are encouraging amateur radio operators to download data from the spacecraft in exchange for using the transponder to carry out radio conversations across distances as vast as the Atlantic Ocean.
		For the radio buffs, having a satellite transponder means they can talk over much greater distances than using only ground radios: "The horizon gets in the way," he explains.
	www.newscientistspace.com /article/dn8217--satellite-to-have-virtual-global-ground-station.html (581 words)

	Technostress in the Bionic Library
		The individual using networked information systems from outside the library is often described in the literature as a "remote user," but for this discussion it is worth noting that from the user's point of view, he/she is central and the library is remote.
		Furthermore, for any individual, the "virtual library" means not only the local library's online system, but also other libraries' systems, and in fact the sum total of information resources to which he/she can connect in some meaningful way.
		Thus architectural concepts, such as rooms, maps, and signposts, are also appropriate tools for library system designers, whether or not the final interface is presented as a "virtual building".
	www.jkup.net /bionic.html (7063 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		Imagine an analog circuit which maintains its input at "virtual ground"-a voltage almost equal to zero.
		With currents IS and IF both shown flowing into the virtual ground, and no current flowing into the op amp, Kirchoff's Current Law requires
		An op amp output responds to input current, as dictated by VS and RS and their associated resistors-it's a current-to-voltage converter.
	www.engin.brown.edu /Faculty/Daniels/ddzo/dachpt.html (7165 words)

	Virtual Targets (VT)
		The Virtual Targets Program is a Targets Management Office (TMO) initiative to provide joint system developers, testers, and evaluators with variable-resolution models of targets to support their life-cycle simulation needs in the face of the Department of Defense(DoD) mandated simulation-based acquisition strategy.
		The program produces Virtual Targets across a spectrum of resolutions to support a range of simulation requirements from low resolution (to support real-time simulation applications) through high resolution (to support engineering/signature analysis activities) with traceability back to the parent geometry.
		TMO develops Virtual Targets in formats common to existing simulations, in compliance with High Level Architecture requirements, and with respect to emerging technologies.
	www.peostri.army.mil /PRODUCTS/VT (187 words)

	diyAudio Forums - Creating the 'virtual ground' in a single supply preamp/amp circuit???
		What is the best way to create a steady mid-rail voltage (VCC/2) for a reference voltage (also known as virtual ground) for the opamps and LM3886 IC's?
		At the moment, I am trying an op amp follower circuit similar to the one shown on page 2 of this document http://www.analogzone.com/avt_0806.pdf (i originally didnt have the small resistor on the output and got oscillations from the op amp.
		The grounds are tied together -- and this is your virtual ground.
	www.diyaudio.com /forums/showthread.php?postid=30795 (344 words)

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