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	Feedback - Wikipedia, the free encyclopedia
		Feedback may be negative, which tends to reduce output, (but in amplifiers, stabilises and linearises operation), or positive, which tends to increase output.
		Negative feedback is often deliberately introduced to increase the stability and accuracy of a system, as in the feedback amplifier invented by Harold Stephen Black.
		Positive feedback amplifies possibilities of divergences (evolution, change of goals); it is the condition to change, evolution, growth; it gives the system the ability to access new points of equilibrium.
	en.wikipedia.org /wiki/Feedback (1448 words)

	Learn more about Feedback in the online encyclopedia. (Site not responding. Last check: 2007-10-20)
		In engineering, economics and biology, feedback is a process whereby some proportion of the output signal of a system is fed back to the input, in order to change the dynamic behaviour of the system.
		Feedback may be negative, thus tending to reduce output, or positive, thus increasing output.
		In engineering control theory, feedback is a process in which a signal generated from the output of a system is applied as an input to the same system.
	www.onlineencyclopedia.org /f/fe/feedback.html (904 words)

	Feedback amplifier - Wikipedia, the free encyclopedia
		A feedback amplifier, also known as negative feedback amplifier is an amplifier which uses a feedback network, generally for improving performance (gain stability, linearity, frequency response etc.).
		Feedback can be negative or positive, but must be negative for overall stability of the system.
		One way to model negative feedback amplifiers is the asymptotic gain model.
	en.wikipedia.org /wiki/Feedback_amplifier (160 words)

	Feedback Amplifiers - Microwave Encyclopedia - Microwaves101.com
		Below is an obsolete low noise amplifier, with series feedback on the input stage (RF input is on the left) and parallel feedback on the second stage.
		Series feedback as it is used in microwave LNAs was patented by Heston and Lehmann of Texas Instruments in 1986 (U.S. patent number 4,614,915, "Monolithic series feedback low noise FET amplifier").
		In parallel (or shunt) feedback, a path is introduced between the output of a FET (drain) and the input (gate), parallel to the signal.
	www.microwaves101.com /encyclopedia/feedbackamp.cfm (635 words)

	Electronics 35
		This is a feedback amplifier, and the bias for the 6AU6's is not supplied by the small cathode current, but by feedback from the plates of the 6V6's, which holds the cathodes of the 6AU6's at 6.7V.
		The effect of the feedback is to hold the voltage gain at 56 (grid of 6AU6 to plate of 6V6), and to decrease any nonlinearities by a factor of 44.
		Fidelity is not limited by the amplifier; the loudspeaker and signal source are far more limiting, and must be considered in relation to the amplifier, which must compensate for their deficiencies.
	www.du.edu /~etuttle/electron/elect35.htm (1941 words)

	Analog Devices: Analog Dialogue: Two-Stage Current-Feedback Amplifier
		Voltage developed at the output of the transconductance stage of a current-feedback amplifier (the high-impedance "C(p)" node) is unloaded by the unity-gain buffer to provide output drive.
		A further advantage of the two-stage amplifier is the higher overall gain-bandwidth (for the same power), which means lower signal distortion and the ability to drive heavier external loads.
		Finally, the amplifier's wide common-mode and output ranges permit it to operate on a single 5-volt supply, with half the power and little degradation of performance over ±5-V operation.
	www.analog.com /library/analogDialogue/archives/29-2/feedback.html (502 words)

	Designing Single-Stage Inverting Feedback Amplifier
		The feedback coupling capacitor, Cc, should be calculated in the same manner as Co in the previous example, because it is dependent upon the value of the feedback resistor, Rf.
		Aside from the potential transient response problems, the single-stage negative feedback amplifier is ideal for use in places where a flat, uncolored, controlled frequency response is desired, and where the low output impedance and controlled input impedance is useful.
		Ri is the input resistance, Rf is the feedback resistance, and Ra is the internal output resistance of the amplifier stage being used.
	www.aikenamps.com /FeedbackAmp.htm (4118 words)

	Amplifier feedback
		Notice that the feedback signal is in phase with the input signal.
		Sometimes feedback that is not desired occurs in an amplifier.
		By adding a negative feedback system, as in view D, the gain of the stage is decreased and the fidelity of the output signal improved.
	www.tpub.com /neets/book8/30e.htm (643 words)

	[No title]
		The first is the fact that, although the feedback amplifiers en- visaged in most of the discussion are of the conventional single loop, absolutely stable type, the original plan for the text called for two final chapters on design methods appropriate for multiple loop and condition- ally stable circuits.
		Since the noise which would appear in the output in the absence of feedback is g2D0, this result is equivalent to the T/eorem: The noise level in the output of a feedback amplifier is reduced by feedback in the ratio (1 - ): 1.
		Feedback is thus a useful tool in combating troubles due to modulation and perhaps power supply hum, in the case of tubes with directly heated cathodes, which are characteristic of output stages.
	auditorymodels.org /jba/BOOKS_Historical/Bode/Bode.txt (20146 words)

	Electronics 7
		Note that the feedback signal is subtracted from the input signal, and tends to reduce the output of the amplifier.
		Negative feedback, applied to a voltage amplifier, divides the gain by the feedback factor (stabilizing it), increases the input resistance by the feedback factor, and decreases the output resistance by the same factor.
		Feedback is of great use in studying the frequency response and stability of amplifiers, but I shall leave that topic for elsewhere.
	www.du.edu /~etuttle/electron/elect7.htm (4860 words)

	The Tube CAD Journal, partial feedback amplifier
		Going by the names of "the partial feedback amplifier" and "the inverse feedback pair amplifier," this circuit topology is defined by the use of a resistor spanning the output tube's output to its input, i.e.
		the wrapping of a feedback loop from the plate to the grid, and as the plate inverts the grid's signal, a negative feedback loop.
		Because the feedback loop is so short, this feedback system finds little of the instability problems usually associated with the use of feedback.
	www.tubecad.com /march2001 (486 words)

	[No title]
		In some sense, this is bad, because the 2 amplifying paths do not have the same high frequency response, which is a distortion producing mechanism as well as complicating the feedback issues.
		This causes another "asymmetric" pole, but this also happens to be the correct phase for negative feedback, and it also happens to be in the path that "lacked" a high frequency pole in the phase inverter stage, potentially "compensating" for it.
		FEEDBACK AND STABILITY ANALYSIS There are 2 feedback loops to deal with on the high frequency side, due to the 100 pF between input cathode and driver plate, and from output to input cathode.
	members.aol.com /sbench101/TubeMisc/fb_faq7.txt (2429 words)

	United States Patent: 4,312,060
		Transient intermodulation distortion is generally caused by the inability of a negative feedback amplifier when presented with a fast changing input signal to feedback a needed feedback component in time to interact with the fast input signal.
		The amplifier section 7 can be any conventional, integrated or discrete component amplifier, with at least two amplifier stages connected in cascade, with the feedback circuit 8 interconnecting the output of the second stage to the input of a feedback point to the input stage.
		The load for the cascode amplifier pair is furnished by a constant current source 40 connected between the B+ bus and a resistor 34, in turn, connected to the collector of transistor 31.
	www.audioannals.com /04312060-Grodinsky-txt.htm (3945 words)

	Feedback Stability FAQ
		The familiar case is a feedback amplifier wherein a square-wave input excites a unique frequency of oscillation at the output.
		Feedback for closed-loop figures: the bottom-tube grid is used as a summing junction.
		For example, if at some frequency an amplifier has an open-loop gain of 100 and the feedback loop is a voltage divider with a 9 K ohm resistor to the amplifier output and a 1 K ohm resistor to ground, then the loop gain is 100 x.1 = 10 at that frequency.
	www.triodeel.com /feedback.htm (8237 words)

	The Tube CAD Journal: 300B Power Amplifier Design Example
		The driver stage in the stock amplifier is a differential amplifier of sorts.
		Feedback is feedback; it can be used in preamps, crossovers, equalizers, line stages, and power amplifiers.
		The power amplifier readily benefits from the greatly lowered plate resistance, as the output transformer has limited amount of inductance, which the lower rp aids.
	www.tubecad.com /march2001/page13.html (332 words)

	Simple 60 Watt Power Amplifier
		Feedback is applied to the emitter of the input transistor, and works in current mode - hence 'current feedback'.
		That the current is derived from a voltage is of little consequence, because this is the case for nearly all feedback circuits.
		One can reduce the value of R5 (the feedback resistor) but then the required capacitance of C4 becomes too high to be sensible because R12 must be reduced for the same audio gain.
	sound.westhost.com /project12.htm (2236 words)

	AMF AMPLIFIERS PRODUCTS (Site not responding. Last check: 2007-10-20)
		Each amplifier stage in a balanced design employs a 90° hybrid at the input and output to feed two discrete transistors.
		Series feedback is also known as "lossless" feedback because there is no additional lossy circuits added to the input of the FET.
		This optimization of a feedback amplifier design involves a tradeoff exercise between input VSWR and noise figure performance.
	www.miteq.com /micro/amps/amfamps/c23b/overview.html (453 words)

	Feedback and fidelity part 2
		In SE tube amplifiers, most of which have little or no feedback, the predominant distortion component is the second harmonic.
		For a tube amplifier to be called truly feedback-free— in the local as well as the global sense— it would have to be built entirely of pentodes.
		Extensive computer simulation and listening have led me to conclude that feedback amplifiers can have flawless sound quality, without a trace of muddiness or grayness, provided that the three dangers of feedback— instability, RF susceptibility, and sharpened clipping— can be eliminated or minimized.
	www.normankoren.com /Audio/FeedbackFidelity2.html (4245 words)

	Amplifier Feedback
		In this case, the amplified guitar waveforms couple back to the strings with some gain and delay, as depicted schematically in Fig.
		The Amplifier Feedback Delay in the figure can be adjusted to emphasize certain partial overtones over others.
		If the loop gain, controllable via the Amplifier Feedback Gain, is greater than 1 at any frequency, a sustained ``feedback howl'' will be produced.
	ccrma-www.stanford.edu /~jos/waveguide/Amplifier_Feedback.html (243 words)

	Current Feedback
		A constant power amplifier has the advantage of delivering constant power across its operational frequency spectra, independent of a varying load (such as a voice coil changing properties under thermal load).
		Since this amplifier is predictable, it is appropriate for heavily equalized systems.
		A current-feedback amplifier uses a sense resistor (Rs) that develops a feedback voltage proportional to the current.
	home.insightbb.com /~stephenwmoore/Speakers/Current_Feedback_Theory.htm (510 words)

	How to Install Dakiom Amplifier Feedback Stabilizers Into Your Existing Audio System
		On a pair of monoblock amplifiers or in the case of a stereo amplifiers with speaker terminals too far apart for a single A203/A103's reach, two A203/A103's must be used.
		In Bridged amplifier configurations, two channels are combined to drive a single speaker (for example, a stereo amplifier bridged to become a mono amplifier).
		The connection of the Feedback Stabilizer to a bridged amplifier is slightly different from that of a normal amplifier (not bridged).
	www.dakiom.com /how_to_install_amp.htm (3088 words)

	Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations (Site not responding. Last check: 2007-10-20)
		Negative feedback amplifiers, and particularly a negative feedback circuit which is economical on amode power consumption, are described.
		Operating potential for screen of the second tube is supplied by connecting the cathode resistor of the first tube to the screen, while the screen is by-passed to the cathode of its tube for the amplified frequencies.
		Also, the amplifier incorporates a circuit to stabilize the transconductance of the tubes by making the grid potential of each tube interdependent on anode currents of both lubes by voltage divider circuitry.
	www.osti.gov /energycitations/product.biblio.jsp?osti_id=4312389 (186 words)

	Current Feedback
		Since this amplifier will be used exclusively from 100Hz to 1440Hz, total bandwidth may only need to be 2 octaves.
		It is expected that a current feedback (high impedance) amplifier will have some sonic benefits over a voltage amplifier due to greater control over the loudspeaker’s voice coil.
		Notice the current drive amplifier’s output is affected by the inverse of the driver’s impedance curve.
	home.insightbb.com /~stephenwmoore/Speakers/Current_Feedback.htm (704 words)

	StereoTimes - Monarchy Audio SM-70 Pro Zero-Feedback Amplifier (Site not responding. Last check: 2007-10-20)
		The amplifier is a Class-A design that eschews the use of ANY global feedback, although some local feedback is employed.
		The switch from stereo to mono configuration is accomplished by flipping a rear panel switch in concert with a swapping of the speaker output taps.
		Summing Up If I could find an amplifier that offered the bass extension and dynamics of the Sonogy Black Knight, the overall harmonic integrity and midrange magic of the Monarchy SM-70 Pro, and the detailed, extended and spacious soundstaging of the InnerSound ESL amp, I would be one happy camper.
	www.stereotimes.com /amp050200.shtm (2299 words)

	Lecture Outline (Site not responding. Last check: 2007-10-20)
		Basic building blocks of an op-amp: a CC-CB compound amplifier is used to demonstrate the evolution of the differential pair.
		Improving the common mode rejection of a simple differential pair using local feedback, as it was the case in Fairchild uA-709.
		The bandwidth of the I to V converter at the output of a translinear circuit is improved using local shunt feedback.
	www.icsl.ucla.edu /aagroup/ee115d/Lec_outline.html (554 words)

	Feedback amplifier
		A feedback amplifier is an amplifier which uses a feedback network, generally for improving performance (gain stability, linearity, frequency response etc.).
		The idea of this invention is simple: if NFB depth is big, overall response of the whole system can be very close to inverted feedback network response.
		The most widely-known realisation of this principle in electronics are circuits, based on operational amplifiers (Op-Amps), such as the old uA741 or LF411.
	www.brainyencyclopedia.com /encyclopedia/f/fe/feedback_amplifier.html (155 words)

	EDN -- 11.09.95 i-feedback amplifier puts parasites to work
		Many an engineer designing with wideband op amps has battled parasitic capacitance at the inverting input.
		What’s more, if you design a discrete gain-select circuit, you must deal with declining amplifier performance at higher gain levels.
		The circuit in Figure 1, using a CLC404 wideband current-feedback amplifier, controls the parasitic capacitance to maintain performance in a discrete gain-select configuration.
	www.edn.com /archives/1995/110995/23di4.htm (390 words)

	Product Folder : THS4001 - 270-MHz Voltage-Feedback Amplifier (Site not responding. Last check: 2007-10-20)
		The THS4001 is a very high-performance, voltage-feedback operational amplifier especially suited for a wide range of video applications.
		The THS4001 is stable at all gains for both inverting and noninverting configurations.
		If the information you are requesting is not available online at this time, contact one of our Product Information Centers regarding the availability of this information.
	focus.ti.com /docs/prod/folders/print/ths4001.html (522 words)

	LM7121 - 175 MHz Tiny Low Power Voltage Feedback Amplifier (Site not responding. Last check: 2007-10-20)
		The LM7121 is a high performance operational amplifier which addresses the increasing AC performance needs of video and imaging applications, and the size and power constraints of portable applications.
		Another key feature of this operational amplifier is stability while driving unlimited capacitive loads.
		Tiny amplifiers are so small that they can be placed anywhere on a board close to the signal source or near the input to an A/D converter.
	www.national.com /pf/LM/LM7121.html (314 words)

	Current Feedback Amplifier operates to 37 V., Texas Instruments, Inc. TI
		Current Feedback Amplifier operates to 37 V. June 29, 2005 - High-voltage Model THS3001HV features slew rate of 6,500 V/µs, 40 ns settling time, 420 MHz bandwidth, and 1.6 nV/rtHz input referred voltage noise.
		The THS3001HV is ideal for large-signal applications requiring excellent transient response, low noise and low distortion, such as in test and measurement, communications and imaging.
		The THS3001HV extends the performance of the THS3001, the industry’s fastest 33V high-speed, current feedback amplifier, to 37V (+/-18.5V) power supply systems to allow for increased output voltage swings up to 33V peak-to-peak and increased common-mode operating range.
	news.thomasnet.com /fullstory/464760/rss/772 (693 words)

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