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	Input impedance - Wikipedia, the free encyclopedia
		The input impedance or load impedance of a circuit or electronic device is the impedance actually experienced by a signal which is connected to its input.
		Generally in audio and hi-fi, the input impedance of components is several times higher than the output impedance connected to them.
		The maximum power at maximum efficiency will be transferred when the impedances are complex conjugate matched throughout the power chain, from the transmitter output, through the transmission line (which may be a balanced pair, a coaxial cable, or a waveguide), to the antenna system, which consists of an impedance matching device and the radiating element(s).
	en.wikipedia.org /wiki/Input_impedance (395 words)

	Impedance bridging - Wikipedia, the free encyclopedia
		In electronics, especially audio and sound recording, an impedance bridging or voltage bridging connection is one which maximizes voltage transfer to the load.
		In systems involving very long lines (such as telephone or cable TV systems), the source, line, and load impedances must be matched to prevent reflections of the signal at the ends of the line from causing reflections and echoes.
		The output impedance of the amplifier is typically in the neighborhood of the impedance of the cables connecting it to the speaker (<0.1 ohm), so DF will drop rather easily.
	en.wikipedia.org /wiki/Impedance_bridging (322 words)

	diyAudio Forums - Constant input impedance polarity switcher
		The Zout in the schematic diagram is the output impedance of the previous stage and was used for simulation.
		In inverting mode the input impedance is equal to R1, in non-inverting mode it is equal to R3.
		The disadvantage of different input impedance for the extremes +1 and -1 are the same as in the first circuit, still 200k vs. 100k.
	www.diyaudio.com /forums/showthread.php?postid=249865 (1075 words)

	Klaus Wogram: The strings and the soundboard
		In engineering terms this relation is referred to as "impedance matching." The loading exerted by the soundboard on the string can be expressed by means of its input impedance (Z), which is defined as the excitation force (F) divided by the resulting velocity (v) at the point of excitation.
		A high value of the input impedance means that a large force must be expended in order to achieve a certain vibration velocity, whereas a low impedance means that a smaller force is sufficient to achieve the same velocity.
		The magnitude of the impedance thus determined is registered by a level recorder, and the phase angle by a second similar instrument.
	www.speech.kth.se /music/5_lectures/wogram/impedance.html (590 words)

	Shure - Products
		Impedance is how much a device resists the flow of an AC signal, such as audio.
		Impedance is similar to resistance which is how much a device resists the flow of a DC signal.
		Impedance matching reduced the number of vacuum tube amplifiers needed which were expensive, bulky, and heat producing.
	www.shure.com /ProAudio/Products/us_pro_ea_imepdance (364 words)

	Klaus Wogram: The strings and the soundboard
		An example of measured input impedance and radiated sound level curves for an upright piano assembly consisting of the wooden frame, soundboard and metal plate, strung and tuned to normal pitch, is shown in Fig.
		It can be seen that the impedance curve is characterized by prominent tall peaks and valleys in the lower part, superimposed on a continual decrease from 100 Hz to the highest frequencies.
		The phase angle is close to -90º, which means that the input impedance is dominated in this region by the resiliency (springiness) of the soundboard.
	www.speech.kth.se /music/5_lectures/wogram/inputimp.html (567 words)

	Interpreting Antenna Performance Parameters for EMC Applications - Part 1 (Site not responding. Last check: 2007-10-31)
		The quality of the input impedance match for an antenna is generally not specified in terms of either reflection coefficient or mismatch efficiency.
		The reason for this is that the balance depends in part on the ratio of the choking impedance of the balun to the antenna's input impedance.
		Input impedance match determines how much incident power is reflected back into the source, while radiation efficiency determines how much incident power is dissipated as heat in the antenna.
	www.djmelectronics.com /articles/emc-antenna-parameters-p1.html (2298 words)

	Impedance FAQ
		Impedance (Z) is the resistance of a circuit to alternating
		The adapter is a tube with a female XLR input and a phone-plug
		Impedance is measured in magnitude (ohms) and phase (degrees)
	www.tape.com /Bartlett_Articles/impedance.html (1214 words)

	Understanding Impedance
		The output voltage from the source is developed across the input impedance of the destination (often called the load impedance, or simply the load), and therefore the signal voltage is passed from source to destination.
		Relatively high-impedance inputs such as these are called bridging inputs, and they have the advantage that several devices can be connected in parallel without decreasing the impedance to any significant degree — the voltage developed across each input remains high and the source does not need to supply a high current.
		The use of the transformer is principally to translate the effective load impedance between that required by the valves, and that of a practical loudspeaker — a typical valve output circuit requires a load of between 5k(omega) and 10k(omega), whereas a practical loudspeaker presents a nominal impedance of between 4(omega) and 15(omega).
	www.soundonsound.com /sos/jan03/articles/impedanceworkshop.asp (5526 words)

	Impedance - What and Why?
		Impedance is the generalization of the concept of resistance from DC to AC.
		The quick and dirty way of measuring input impedance with a variable resistor to halve the input voltage works, and gives a correct number at every frequency, but it gives you no insight into what is happening with frequency until you do enough points to find the turnover frequency.
		In most cases, the real trick is to make the input and output impedances not matter: that is, you make input impedances large compared to the output impedances of whatever the signal source is, and make output impedances tiny compared to the load it's driving.
	www.geofex.com /Article_Folders/impednc.htm (1470 words)

	Differential amplifier circuit arrangement with stabilized input impedance - Patent 4276515
		This means that the input impedance of the differential amplifier as viewed from the terminal 6 changes in response to the input signal applied thereto.
		An input terminal 38 and an output terminal 40 of the amplifier circuit are connected to current-control electrode, i.e.
		Hence, the input impedance of the amplifier circuit as viewed from the input terminal 38 is prevented from fluctuating during operation, and as a result, there can be prevented such distortion of the output signal as may be caused due to non-linear variations in the input impedance of the amplifier circuit.
	www.freepatentsonline.com /4276515.html (1949 words)

	SIGRITY Support Page(Tech Paper 1)
		The amplitude of the input impedance from DC to 1GHz of the power and ground plane structure looking from the pair of the vias at the center is shown in Figure 6.
		High input impedance no longer exists at the low frequency region, which means that the power and ground plane structure is not capacitive at low frequencies.
		The input impedance is shown in Figure 10, and the effective input inductance in the low frequency range is displayed in Figure 11.
	www.sigrity.com /papers/InputImp/InputImp.htm (921 words)

	Electrical/Electronic engineering other topics - Measuring input impedance
		I have been asked to measure the actual input impedance of an analog circuit that is designed to accept micro volts as the input which is directly fed into a high impedance op-amp buffer stage.
		To actually measure the input impedance the easiest way is apply your input signal, eg 2v in your case, for which you'll get 2v o/p from your op-amp and then insert a resistance in series with the input to decrease the o/p to 1v.
		Measuring the input impedance and changing the ic type to a jfet or lower impedance op-amp proably won't help unless very low level noise is an issue, in which case quieter components are available.
	www.eng-tips.com /viewthread.cfm?qid=72431 (1327 words)

	Abstracts - Input Filter Interaction
		Preferably, a suitable input filter should be incorporated in original regulator design; criteria are developed for input filter resonant frequency and Q that ensure not only system stability but also specified perturbations of the important regulator properties, loop gain, output impedance, and line rejection.
		Consequently, criteria for input filter design in the presence of a significant source impedance are developed, which, when used in conjunction with already-known input filter criteria, permit the input filter to be designed so that the entire system operates reliably.
		Consequently, criteria for input filter design in the presence of a significant source impedance are developed, which, when used in conjunction with already-known input filter criteria, permit the input filter to be designed so that each regulator operates reliably.
	www.smpstech.com /filtebib.htm (3120 words)

	Learn Electronics Lessons and Information Pages
		Impedance consists of the vector sum of resistance and reactance.
		Matching the output impedance of a source to the input impedance of a load to attain maximum power transfer.
		A device that approximates and whose output is proportional to an integral of the input signal.
	www.twysted-pair.com /dicti.htm (581 words)

	Measuring Input Impedance - Spring 1997 (Site not responding. Last check: 2007-10-31)
		The input impedance of the circuit is the reflected impedance of the emitter multiplied by the beta of the transistor.
		Since the impedance is equivalent to the voltage across the source, the waveform V(2) has been chosen to plot the magnitude of the impedance.
		The second plot is the phase of the impedance, and this waveform is plotted through the expression ph(V(2)).
	www.spectrum-soft.com /news/spring97/input.shtm (321 words)

	ePanorama.net
		Output impedance may be determined using this simple technique: A load resistor is used to load the signal source.
		The input or output impedance of a two terminal network can be determined by measuring the small signal AC currents and voltages.
		The classical measuremetn for the the input is the following: the voltage is measured across the input terminals and the current measured by inserting the meter in series with the signal generator.
	www.epanorama.net /index.php?index=calc_impedance (361 words)

	Impedance and Reactance
		Impedance (symbol Z) is a measure of the overall opposition of a circuit to current, in other words: how much the circuit impedes the flow of current.
		The term 'impedance' is often used (quite correctly) for simple circuits which have no capacitance or inductance - for example to refer to their 'input impedance' or 'output impedance'.
		For successful use the output impedance of the voltage divider should be much smaller than the input impedance of the circuit it is connected to.
	www.kpsec.freeuk.com /imped.htm (1171 words)

	Technical Glossary -"A" (Site not responding. Last check: 2007-10-31)
		Input Impedance: The resistance measured across the excitation terminals of a transducer at room temperature, with no load applied, and with the output terminals open-circuited.
		In the case of a voltmeter, this resistance has to be taken into account when the source impedance is high; in the case of an ammeter, when the source impedance is low.
		Input Resistance (Impedance): The input resistance of a pH meter is the resistance between the glass electrode terminal and the reference electrode terminal.
	www.flw.com /define_i.htm (789 words)

	Interfacing: Impedance and Signal Level
		The "low impedance" microphone input on a mixer: Most mics are specified as being something on the order of 150 Ohms.
		The resultant input impedance is: 2K Ohms - the same as the mic input.
		Because the amp's input is an XLR, and a DI's output is an XLR, I often see folks recommend the use of a DI (Direct Box).
	www.padrick.net /LiveSound/Interfacing.htm (973 words)

	Compute Load Impedance from Measured Input Impedance for any Length and Impedance Feedline
		The input impedance of an inaccessible radio antenna can by obtained by calculating what it must be to give the impedance measured at the input end of the antenna's feed line.
		Line input impedance may be entered in the form of either series or parallel values of R and X. On changing previously entered values of R or X, parallel or series equivalents are immediately displayed.
		First time round it is possible to enter only the series R and X components of input Z. The load (terminating) impedance is computed and displayed in three equivalent forms: magnitude and angle, series and parallel R and X. The exact length in wavelengths of the antenna feeder is important.
	www.smeter.net /feeding/zl_zin.php (1030 words)

	Line signal to microphone input
		This equation is quite accurate when the impedance of the mic input where this circuit is connected has much higher impedance than the resistance of R2.
		Typical microphone inputs in equipments have input impedance of 1.5 kohm or higher (which is much higher than 100 ohms).
		Unbalanced microphone inputs of audio equipments are very sentitive to all noise in the system, especially when you connect something else than a flowating microphone to them.
	www.epanorama.net /circuits/line_to_mic.html (736 words)

	Impedance Matching of Audio Components
		The maximum power transfer from an active device like a microphone to an amplifier occurs when the impedance of amplifier input matches that of the source device.
		If a high impedance microphone (50,000 ohms) is connected directly to a low impedance input (600 ohms), it will deliver only about 5% of the power you get if impedance matched (13 dB less signal).
		If a low impedance microphone (600 ohms) is connected directly to a high impedance input (50000 ohms), it will likewise deliver only about 5% of the power you would get when impedance matched (a 13 dB loss).
	hyperphysics.phy-astr.gsu.edu /hbase/audio/imped.html (575 words)

	Input impedance
		Note that the pitch perceived by a human listener is the same as that for a sinusoidal oscillation at the fundamental of the harmonic series even when the component of the fundamental actually present in the sound is very weak.
		The input impedance is the ratio of the pressure and volume velocity at the input or mouthpiece end.
		In terms of brass instruments this means the input impedance gives a measure of the sound pressure amplitude in the mouthpiece due to a given amplitude of sinusoidal excitation created by the varying flow of air between the lips.
	www.ph.ed.ac.uk /~jonathan/thesis/node11.html (564 words)

	Technical Tidbit - April 2001 - Measurement Error Caused by Probe Input Impedance
		The capacitive reactance of the probe's input capacitance is given by equation (2).
		This input impedance is not much higher than many of the signals likely to be probed on a printed wiring board.
		If we assume circuit impedance on the order of 50 Ohms for a printed wiring board and would like the probe to be ten times the circuit impedance, then the probe should have a 500 Ohm input impedance at the highest frequency at which the signal has significant components.
	www.emcesd.com /tt2001/tt040101.htm (521 words)

	Measuring Input and Output Impedance (Site not responding. Last check: 2007-10-31)
		From the AC impedance triangle, the input or output impedance of a two terminal network can be determined by measuring the small signal AC currents and voltages.
		For the input, the voltage is measured across the input terminals and the current measured by inserting the meter in series with the signal generator.
		The input impedance of the circuit under test is then found from V1 / Iin.
	www.mitedu.freeserve.co.uk /Theory/inzoz.htm (508 words)

	OHM SWEET OHM
		In a purely resistive circuit, resistance and impedance are the same thing, but in the case of a reactive circuit (one containing capacitors or inductors), the impedance will vary depending on the frequency of the signal being applied.
		A cyclist has an output impedance related to his or her ability to turn the pedals, whereas the pedals themselves have an input impedance -- they put up resistance to being turned.
		When matching amplifiers to loudspeakers, the output impedance of the amplifier should match that of the loudspeakers as accurately as possible, to ensure that the amplifier is able to deliver its maximum rated power.
	www.soundonsound.com /sos/1994_articles/oct94/impedance.html?session=43bd08c9b3a387969045286fdd2be627 (1438 words)

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