Frequency Responsive Feedback Means Patents (Class 330/109)
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Patent number: 5953430Abstract: A filter circuit adjustably decreases or increases the amplitude of audio signals in a predetermined frequency range. The filter circuit includes a filter module having an RC network with at least one frequency-response-determining RC member whose resistor component R is realized in SC technology. A setting device is connected to the filter module such that its setting determines the frequency response of the SC filter. The setting device renders possible a neutral setting in which the effective audio signal path of the filter circuit circumvents the filter module so that no decrease or increase of the amplitude of individual frequency portions takes place. Furthermore, an audio signal processor comprises at least one audio signal input, at least one audio signal output, and at least one control input.Type: GrantFiled: July 25, 1997Date of Patent: September 14, 1999Assignee: STMicroelectronics GmbHInventors: Peter Kirchlechner, Jorg Schambacher, Jurgen Lubbe
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Patent number: 5945874Abstract: A circuit configuration for smoothing an input voltage includes two input terminals for receiving the input voltage. A negative-feedback amplifier has two inputs and an output. A capacitor is connected to one of the inputs of the amplifier. An output terminal is connected to the output of the amplifier. A converter element has a first terminal connected to one of the input terminals, a second terminal connected to the one input of the amplifier and to the capacitor, and a third terminal connected to the output of the amplifier.Type: GrantFiled: July 19, 1996Date of Patent: August 31, 1999Assignee: Siemens AktiengesellschaftInventors: Manfred Punzenberger, Bernhard Zojer
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Patent number: 5929698Abstract: A low-pass filter circuit including a first sub-filter designed in integrated circuit technology. The first sub-filter includes high-impedance resistor elements and smaller capacitances. A second sub-filter preceding the first sub-filter is constructed with low-impedance resistor elements and higher capacitances.Type: GrantFiled: July 8, 1997Date of Patent: July 27, 1999Assignee: Siemens AktiengesellschaftInventors: Stephan Weber, Volker Thomas
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Patent number: 5923206Abstract: An MOS FET circuit with a summing circuit at the input of an amplifier to provide charge cancellation. The summing circuit is capacitively coupled to the input with a charge cancellation capacitor. A separate amplifier, having components substantially the same as the components of the first amplifier, is connected through the charge cancellation capacitor to the first amplifier.Type: GrantFiled: March 27, 1997Date of Patent: July 13, 1999Assignee: Exar CorporationInventor: Roger A. Levinson
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Method and apparatus for detecting and compensating for undesired phase shift in a radio transceiver
Patent number: 5894496Abstract: The present invention provides a method and apparatus for detecting and compensating for transmitter phase shift in a radio transmitter. A local oscillator generates a local oscillator signal. A modulator such as an I/Q modulator modulates input signals onto the local oscillator signal to generate a forward signal. That forward signal is amplified and otherwise prepared for transmission via an antenna. The transmitted signal is detected, and a phase adjuster substantially continuously detects and cancels undesired phase shifts in the detected signal caused by elements in the radio chain. A specific, example embodiment of the present invention is provided in a Cartesian feedback system wherein the phase of the feedback signal is detected and aligned with the phase of the original modulated signal, providing uncorrupted I and Q baseband feedback signals.Type: GrantFiled: September 16, 1996Date of Patent: April 13, 1999Assignee: Ericsson Inc.Inventor: Mark Alan Jones -
Patent number: 5890058Abstract: In an FDNR type active filter fabricated on an integrated circuit, an FDNR circuit is provided wherein one ends of a first capacitor and an impedance element are connected to an inverted input of an operational amplifier, one ends of the impedance element and a second capacitor are connected to an output end of the operational amplifier, and the other ends of the first and second capacitors are connected to each other. To the impedance element, resistors are connected in series. To the connecting end of the resistors, one end of another resistor is connected, the other end thereof being grounded in an alternating current form. The capacity value of the second capacitor is greater than that of the first capacitor.Type: GrantFiled: September 18, 1996Date of Patent: March 30, 1999Assignee: Kabushiki Kaisha ToshibaInventors: Takashi Ueno, Tetsuro Itakura, Hiroshi Tanimoto
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Patent number: 5872466Abstract: A matched filter with reduced electric power consumption is disclosed. The matched filter circuit power consumption is reduced by stopping the electric power supply to an unnecessary circuit since input signal is partially sampled just after an acquisition. Since the spreading code is 1 bit data string, the input signal sampled and held is branched out into the signal groups "1" and "-1" by a multiplexer. The signals in each groups are added in parallel by a capacitive coupling, and the electric power is supplied in the circuit intermittently.Type: GrantFiled: July 26, 1996Date of Patent: February 16, 1999Assignees: Yozan Inc., Sharp Kabushiki KaishaInventors: Guoliang Shou, Changming Zhou, Makoto Yamamoto, Sunao Takatori
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Patent number: 5852359Abstract: A voltage regulator with load pole stabilization is disclosed. The voltage regulator consists of an error amplifier, an integrator which includes a switched capacitor, a pass transistor, and a feedback circuit. In one embodiment, the integrator circuit includes an amplifier, a capacitor, and a switched capacitor which is driven by a voltage controlled oscillator. The voltage controlled oscillator changes its frequency of oscillation proportional to the output current. In another embodiment, the switched capacitor is driven by a current controlled oscillator whose frequency of oscillation is also proportional to the output current of the voltage regulator. When the output current demand is large, the controlled oscillators increase the frequency which decreases the effective resistance of the switched capacitor thereby changing the frequency of the zero to respond to the change in the load pole.Type: GrantFiled: July 8, 1997Date of Patent: December 22, 1998Assignee: STMicroelectronics, Inc.Inventors: Michael J. Callahan, Jr., William E. Edwards
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Patent number: 5828264Abstract: A two stage operational amplifier circuit comprises a first stage (31) having an input (2, 4) and an output, and a second stage (33) having an input and an output (19). The second stage input is coupled to receive the first stage output. A feedback path (41, 45, 47, 51) is coupled between the output and the input of the second stage. The feedback path (41, 45, 47, 51) comprises a low-frequency compensation path (41, 45) and high-frequency compensation path (45, 47, 51). The feedback path (41, 45, 47, 51) is compensated such that the frequency response of the second output of the second stage is substantially 6 dB per octave throughout the high-frequency region.Type: GrantFiled: December 7, 1995Date of Patent: October 27, 1998Assignee: Motorola, Inc.Inventors: Vladimir Koifman, Yachin Afek
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Patent number: 5796305Abstract: A circuit for increasing damping factor in an audio amplifier adapted to be coupled to a load by output feed and return leads and components having an impedance causing a reduction in the damping factor, employs a balanced feedback network having first and second inputs and first and second outputs. The first input is coupled to a selected one of the feed and return lead near the output terminal and the second input is coupled to the same lead remote from the output terminal to thereby establish a series impedance between said first and second inputs representative of impedance of the selected output lead. The first output is coupled to the non-inverting input of the amplifier and the second output is coupled to the inverting input of the amplifier. The balanced feedback network positively feeds back a representation of the impedance to compensate therefor and thereby raise the damping factor of the amplifier. In an alternative embodiment, an isolating transformer is employed in the balanced feedback network.Type: GrantFiled: June 14, 1996Date of Patent: August 18, 1998Assignee: Peavey Electronics CorporationInventor: Jack C. Sondermeyer
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Patent number: 5767743Abstract: An RF power amplifier includes an input-side tertiary harmonic wave control circuit and an output-side tertiary harmonic wave control circuit, respectively connected to a gate and a drain of a signal amplification FET. The RF power amplifier also includes a tertiary harmonic wave feedback circuit connected in parallel with the signal amplification FET. The tertiary harmonic wave feedback circuit includes an input-side tertiary harmonic wave bandpass filter, a tertiary harmonic wave amplification FET, a phase shifter and an output-side tertiary harmonic wave bandpass filter. These circuit elements are connected in series. Due to such a configuration, a voltage waveform and a current waveform each having a nearly rectangular shape can be easily generated at an output terminal (a drain) of the signal amplification FET, not only in the region around the efficiency saturation point whore the FET operates in a non-linear mode, but also in other linear-operation regions.Type: GrantFiled: October 10, 1996Date of Patent: June 16, 1998Assignee: Matsushita Electric Industrial Co., Ltd.Inventors: Shigeru Morimoto, Masahiro Maeda
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Patent number: 5726600Abstract: An active filter circuit component includes an all NPN bipolar tunable Gm cell and a positive current source (PCS) for supplying common mode current. The tunable Gm cell includes a fixed Gm cell having transconductance G.sub.f, a current divider and recombination circuit that together effectively multiply G.sub.f by a tuning factor .alpha., where -1.ltoreq..alpha..ltoreq.1, without effecting the cell's common mode current I.sub.cm. The PCS includes a pair of unity gain inverting single ended amplifiers that are connected in antiparallel across a pair of matched resistors. Alternately, the resistors can be connected across the inverting and non-inverting sides of a differential amplifier. A constant voltage is applied across the resistors to supply I.sub.cm, while maintaining a common mode resistance of R/2 and a differential mode resistance approaching infinity.Type: GrantFiled: January 17, 1996Date of Patent: March 10, 1998Assignee: Hughes Aircraft CompanyInventors: Gopal Raghavan, Joseph F. Jensen, Albert E. Cosand
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Patent number: 5701100Abstract: A second-order highpass difference filter constructed according to the present invention includes a difference amplifier and a feedback processing circuit. The difference amplifier includes an operational amplifier OP.sub.1, and four resistors R.sub.1, R.sub.2, R.sub.3 and R.sub.4. The feedback processing circuit is composed of two operational amplifiers OP.sub.2 and OP.sub.3, resistors R.sub.5 and R.sub.6, and two serial capacitors C.sub.1 and C.sub.2. The inverting and noninverting terminals of the operational amplifier OP.sub.3 are connected to the output of the difference amplifier and of the operational amplifier OP.sub.2, respectively. The output of the operational amplifier OP.sub.2 is also fed back to the inverting terminal of the operational amplifier OP.sub.2 via the resistor R.sub.5, and the noninverting terminal of the operational amplifier OP.sub.2 is grounded. The output terminal of the operational amplifier OP.sub.3 is connected to the inverting terminal of the operational amplifier OP.sub.Type: GrantFiled: September 10, 1996Date of Patent: December 23, 1997Assignee: National Science CouncilInventors: Chien-Ping Wu, Chang-Da Tsai
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Patent number: 5680072Abstract: A differential, interpolating, switched capacitor filter and method of operation in which non-interpolating stages of the filter are clocked at a first frequency and a subsequent interpolating stage of the filter is operated at double the first frequency to achieve improved smoothing of the output wave form. The switched capacitors in the interpolating stage which feed forward a differential input from a prior stage to an input to the interpolating stage, and which feed a differential output from the interpolating stage back to an input thereto are paired and switches are provided for the added capacitors so that all of these capacitors are switched. Capacitors which are directly coupled to feed forward a differential input from a prior stage to the interpolating stage are also paired, but only the added capacitor is switched.Type: GrantFiled: January 24, 1996Date of Patent: October 21, 1997Assignee: Harris CorporationInventors: Salomon Vulih, George Roalnd Briggs
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Patent number: 5666083Abstract: A circuit and method for adjusting a cutoff frequency of an active filter, such as a gm-C filter, which has a common mode feedback circuit for providing a bias signal may include plural common base stages having first inputs connected in parallel to a stage of the active filter and second inputs connected in parallel to an output from the common mode feedback circuit, and a capacitor connected to an output from each of the common base stages. The common base stages and their connected capacitors are selectively isolated from the filter output to adjust the cutoff frequency of the filter. The deselected common base stages are also isolated from the common mode feedback circuit and bias generator inputs.Type: GrantFiled: November 17, 1995Date of Patent: September 9, 1997Assignee: Harris CorporationInventors: Brent A. Myers, Scott G. Bardsley
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Patent number: 5661435Abstract: An amplifier circuit provides wide bandwidth low noise performance by minimizing the effect of a pole created by the feedback resistor and the capacitance of the input device, such as a photodiode. This is accomplished by shifting the dominant pole to higher frequencies in the amplifier disclosed. A first amplifier stage receives a signal from an input device, such as the photodiode, and feedback from a second amplifier stage. The first amplifier stage is connected to the second amplifier stage such that a lower gain stage is employed to eliminate the phase shift which occurs if the amplifier alone is used in open loop form. The output of the low gain stage is provided to a second amplifier stage with associated gain setting components such that the dominant pole of the overall amplifier is shifted to a higher frequency, typically two decades higher than available from the single stage open loop amplifier.Type: GrantFiled: June 7, 1995Date of Patent: August 26, 1997Assignee: PSC, Inc.Inventor: Edward P. Coleman
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Patent number: 5648718Abstract: A voltage regulator with load pole stabilization is disclosed. The voltage regulator consists of an error amplifier, an integrator which includes a switched capacitor, a pass transistor, and a feed back circuit. In one embodiment, the integrator circuit includes an amplifier, a capacitor, and a switched capacitor which is driven by a voltage controlled oscillator. The voltage controlled oscillator changes its frequency of oscillation proportional to the output current. In another embodiment, the switched capacitor is driven by a current controlled oscillator whose frequency of oscillation is also proportional to the output current of the voltage regulator. When the output current demand is large, the controlled oscillators increase the frequency which decreases the effective resistance of the switched capacitor thereby changing the frequency of the zero to respond to the change in the load pole.Type: GrantFiled: September 29, 1995Date of Patent: July 15, 1997Assignee: SGS-Thomson Microelectronics, Inc.Inventor: William Ernest Edwards
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Patent number: 5625317Abstract: A high-frequency integrated continuous-time filter with built-in test mode. The present invention provides the ability to easily track the cutoff frequency of the filter without the additional power and area requirements and noise sources present in prior art master/slave tuning schemes. Furthermore, the filter being tested is the actual filter that is used to process signals, unlike the prior art where a similar but separate filter or oscillator is used to tune the bias values for both circuits. Better tuning accuracy is thus obtained in the present invention. The circuit is designed to oscillate in test mode at the cutoff frequency of the filter. Oscillation is achieved by moving the poles of the filter from the left half-plane either onto the imaginary axis or into the right half-plane.Type: GrantFiled: August 8, 1994Date of Patent: April 29, 1997Assignee: Texas Instruments IncorporatedInventor: Geert Deveirman
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Patent number: 5610551Abstract: A filter circuit includes a differential amplifier having a mutual conductance of g.sub.m1, and a transistor T.sub.1 which attenuates an output current of the differential amplifier by 1/.beta. (.beta. is a current amplification factor) is arranged at a stage succeeding to the differential amplifier, whereby terms of g.sub.m1 in equations respectively representative of a resonance frequency .omega..sub.0 and a quality factor Q are multiplied by 1/.beta., respectively. Since the term of g.sub.m1 exists in a numerator within a root symbol (.sqroot. ) in the equation representative of the resonance frequency .omega..sub.0, by arranging the transistor T.sub.1, the resonance frequency .omega..sub.0 can be decreased by 1/.sqroot. .beta. times. Furthermore, since the term of g.sub.m1 exists in a denominator within a root symbol (.sqroot. ) in the equation representative of the quality factor Q, by arranging the transistor T.sub.1, the quality factor can be increased by .sqroot. .beta. times.Type: GrantFiled: January 25, 1995Date of Patent: March 11, 1997Assignee: Sanyo Electric Co., Ltd.Inventor: Nobukazu Hosoya
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Patent number: 5606280Abstract: A band-pass filter system comprises a band-pass filter, and a frequency band controller for controlling a frequency band of the band-pass filter by generating a corresponding up pulse voltage and a down pulse voltage according to a pre-controlled center frequency obtained from an output frequency of the band-pass filter to produce a control frequency for obtaining a desired center frequency of the band-pass filter.Type: GrantFiled: October 6, 1995Date of Patent: February 25, 1997Assignee: LG Semicon Co., Ltd.Inventor: Ki S. Sohn
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Patent number: 5542096Abstract: A transmitter that includes an amplifying element, an antenna, a gain stage, and a closed loop feedback may compensate for varying antenna loads without an isolator. This may be accomplished by determining the effects of the varying loading on overall loop gain. Knowing the effects, the transmitter adjusts the gain of the gain stage to maintain a constant overall loop gain, thus eliminating the need for an isolator.Type: GrantFiled: January 27, 1995Date of Patent: July 30, 1996Assignee: Motorola, Inc.Inventors: Lawrence F. Cygan, Paul H. Gailus, William J. Turney
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Patent number: 5523719Abstract: A digitally driven, analog bandpass filter has an analog summer and two analog delay elements connected in a loop. An input signal to the filter is applied to a plus input terminal of the summer, and the output of the second delay elements is applied to a minus input terminal of the summer. The output of filter may be taken either from the output of the summer, or from the output of the second delay element, or from any point in between. Each delay element is driven by a two phase non-overlapping clock, and each element passes a charge from a first capacitor through an op amp to either a second capacitor (first phase) or a third capacitor (second phase). Amplification may be provided by adjusting the ratio of the second (or third) capacitor to the first capacitor. If a differential op amp is used, both sides of the op amp are clocked together, and each side has its own trio of capacitors identical to the trio on the other side.Type: GrantFiled: February 15, 1994Date of Patent: June 4, 1996Assignee: Rockwell International CorporationInventors: Lorenzo L. Longo, Raouf Halim, Bor-Rong Horng
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Patent number: 5504456Abstract: An amplifier circuit provides wide bandwidth low noise performance by minimizing the effect of a pole created by the feedback resistor and the capacitance of the input device, such as a photodiode. This is accomplished by shifting the dominant pole to higher frequencies in the amplifier disclosed. A first amplifier stage receives a signal from an input device, such as the photodiode, and feedback from a second amplifier stage. The first amplifier stage is connected to the second amplifier stage such that a lower gain stage is employed to eliminate the phase shift which occurs if the amplifier alone is used in open loop form. The output of the low gain stage is provided to a second amplifier stage with associated gain setting components such that the dominant pole of the overall amplifier is shifted to a higher frequency, typically two decades higher than available from the single stage open loop amplifier.Type: GrantFiled: February 9, 1994Date of Patent: April 2, 1996Assignee: PSC, Inc.Inventor: Edward P. Coleman
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Patent number: 5483681Abstract: An apparatus for compensating the phase rotation in the feedback loop of a cartesian feedback power amplifier in a final transmitter stage for quadrature modulation of the complex difference signal between a complex input signal and the corresponding complex feedback signal with a complex modulation signal for forming a modulated real valued first signal and for quadrature modulation of the output signal from the power amplifier with a complex demodulation signal for forming the complex feedback signal. The phase shift between the first signal and the second signal and between the quadrature component of the first signal and the second signal is detected for determining the phase rotation of the feedback loop. Furthermore, the phase rotation of the complex modulation signal can be changed with a compensating phase rotation defined by the determined phase rotation.Type: GrantFiled: August 24, 1993Date of Patent: January 9, 1996Assignee: Telefonaktiebolaget LM EricssonInventors: Par S. T. Bergsten, Jan-Christian Nystrom
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Patent number: 5399993Abstract: High input impedance amplifiers are provided which reduce the input impedance solely to a capacitive reactance, or, in a somewhat more complex design, provides an extremely high essentially infinite, capacitive reactance. In one embodiment, where the input impedance is reduced in essence, to solely a capacitive reactance, an operational amplifier in a follower configuration is driven at its non-inverting input and a resistor with a predetermined magnitude is connected between the inverting and non-inverting inputs. A second embodiment eliminates the capacitance from the input by adding a second stage to the first embodiment. The second stage is a second operational amplifier in a non-inverting gain-stage configuration where the output of the first follower stage drives the non-inverting input of the second stage and the output of the second stage is fed back to the non-inverting input of the first stage through a capacitor of a predetermined magnitude.Type: GrantFiled: August 26, 1993Date of Patent: March 21, 1995Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space AdministrationInventor: Leonard L. Kleinberg
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Patent number: 5379009Abstract: An active-type band pass filter achieves a compact structure and a minimum noise figure by setting a coupling Q factor (Q.sub.e1) on an input side of an amplifier, a coupling Q factor (Q.sub.e2) on an output side of the amplifier, and a gain G of the amplifier so that they satisfy the condition that Q.sub.e1 <Q.sub.e2 and 1/Q.sub.e1 =G/Q.sub.e2. By increasing the term with the negative symbol in the equation ##EQU1## the total no-load Q factor (Q.sub.o) is set in the negative region.Type: GrantFiled: July 15, 1993Date of Patent: January 3, 1995Assignee: Murata Manufacturing Co., Ltd.Inventors: Youhei Ishikawa, Seiji Hidaka
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Patent number: 5371472Abstract: A charge amplifier for sensors outputting electrical charge, particularly for piezoceramic pressure sensors, includes a voltage integrator having an output, an integration capacitor and a resistor connected parallel to the integration capacitor. A current-to-voltage converter is connected upstream of the voltage integrator and has an input. A negative feedback branch has a series circuit of a farther voltage integrator and a voltage-to-current converter. The negative feedback branch is connected between the output of the voltage integrator and the input of the current-to-voltage converter.Type: GrantFiled: January 14, 1993Date of Patent: December 6, 1994Assignee: Siemens AktiengesellschaftInventor: Franz Wohlstreicher
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Patent number: 5332937Abstract: A transconductor differential stage for high-frequency filters, which has a MOS differential input pair with common sources. The drain of each MOS input is connected to the emitter of an npn bipolar. These two matched bipolars have their gates connected together with the gate of a third bipolar, which is diode-connected. Two matched current sources feed the two bipolars, and a third current source feeds the third bipolar. A single controlled current sink is connected to the sources of both MOS input transistors, and also (through a resistor) to the third bipolar.Type: GrantFiled: September 9, 1992Date of Patent: July 26, 1994Assignee: SGS-Thomson Microelectronics, S.r.l.Inventors: Rinaldo Castello, Roberto Alini, Andrea Baschirotto, Gianfranco Vai
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Patent number: 5327027Abstract: A circuit is described herein which effectively multiplies the value of a capacitor. The circuit draws current from an input node, where this current being drawn is related to the gain of an amplifier and the value of a capacitor, thus effectively amplifying the capacitance value of a capacitor as seen at the input node.Type: GrantFiled: December 24, 1991Date of Patent: July 5, 1994Assignee: TriQuint Semiconductor, Inc.Inventor: Stewart S. Taylor
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Patent number: 5317277Abstract: The invention features power amplifying apparatus with controllable frequency characteristic of the gain. The apparatus includes a band pass network of two cascaded amplifiers and multiple resistors and capacitors arranged to form multiple feedback loops. The feedback loops stabilize the output A.C. signals and establish a predetermined bandwidth of the network. The apparatus also includes a capacitor resistor feedback loop, connected to the output of the second amplifier and input of the first amplifier, with the capacitor and the resistor selected to maximize the loop gain at a desired frequency.Type: GrantFiled: December 8, 1992Date of Patent: May 31, 1994Assignee: Doble Engineering CompanyInventor: George A. Cavigelli
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Patent number: 5197102Abstract: In a particular embodiment, an audio amplifier drives a load in the form of a sound producing loud speaker exhibiting a frequency variable impedance characteristic over a range of audio frequencies. Voltage and current feedback circuits respectively establish a minimum voltage feedback and a feedback characteristic representative of the load. A presence feedback circuit couples the voltage feedback circuit to ground for reducing feedback with increasing frequency above a selected level whereby the damping factor of the amplifier is reduced. A resonance feedback circuit coupled in parallel with the voltage feedback circuit reduces voltage feedback with decreasing frequencies below the selected level whereby the damping factor is accordingly reduced. The amplifier is responsive to the reduced damping factor for increasing power to the load for enhancing the sound produced by the loud speaker.Type: GrantFiled: January 14, 1991Date of Patent: March 23, 1993Assignee: Peavey Electronics CorporationInventor: Jack C. Sondermeyer
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Patent number: 5187445Abstract: A tuning circuit (30) provides selection signals to a passive component array (80) in a continuous-time filter (70) to compensate for wide variations in values which are encountered in integrated circuit processing. The tuning circuit (30) includes at least one capacitor (46) and at least one resistor (31), and a plurality of either capacitors or resistors. A largest component is enabled and an integration of a reference current during a predetermined period is performed. If the integration provides a voltage greater than a reference voltage, then a corresponding selection signal is set and the component is selected. Successive integrations are performed to determine which components are enabled by corresponding selection signals in order to enable a combination of components which most closely integrates the reference current to the reference voltage. When selection signals corresponding to all components have been determined, the selection signals are applied to corresponding components in the filter (70).Type: GrantFiled: October 28, 1991Date of Patent: February 16, 1993Assignee: Motorola, Inc.Inventor: H. Spence Jackson
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Patent number: 5182522Abstract: A polar leapfrog filter includes at least one polar network. The polar network comprises a differentiator constituted by an operational amplifier having input and output terminals, and a first integrator formed by a first capacitor for providing negative feedback to the operational amplifier and a first variable transconductance amplifier; and a second integrator formed by a second capacitor for providing negative feedback to the first integrator, and a second variable transconductance amplifier. A differentiator is provided at each of the input and output stages of the filter. In the case where two or more said polar networks are incorporated, an additional differentiator is provided between the polar networks. The total number of all the circuit units constituting the filter is selected to provide odd order and equal order for the filter. The circuit units are connected in such a manner that leapfrog type negative feedback is effected.Type: GrantFiled: April 3, 1992Date of Patent: January 26, 1993Assignee: Toko, Inc.Inventors: Hiroshi Tanigawa, Hiroshi Kondo, Isao Fukai, Tsuneo Tohyama
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Patent number: 5175879Abstract: A linear amplifier comprising a feedback loop is stabilized by determining phase error between an error signal and a feedback signal and shifting the phase of a forward signal accordingly.Type: GrantFiled: April 25, 1991Date of Patent: December 29, 1992Assignee: Motorola, Inc.Inventors: David B. Ellingson, Walter J. Rozanski, Jr.
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Patent number: 5095283Abstract: An amplifier circuit includes a high-gain amplifier, and a feedback circuit for extracting an unstable output having a level equal to or less than a threshold level from an amplified signal from the amplifier and for feeding back the unstable signal to the amplifier, so that the amplifier oscillates at a predetermined oscillation frequency. The amplifier circuit also includes a band rejection filter for passing signal components of the amplified signal other than an oscillation output which is obtained at the output terminal of the amplifier when the amplifier oscillates at the predetermined oscillation frequency. The signal components obtained from the band rejection filter are an output signal of the amplifier circuit.Type: GrantFiled: February 7, 1991Date of Patent: March 10, 1992Assignee: Fujitsu LimitedInventors: Kazuhiko Kobayashi, Hiroshi Kurihara, Naofumi Okubo, Yoshihiko Asano, Yoshimasa Daido, Shuji Kobayakawa, Toru Maniwa
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Patent number: 5084683Abstract: The filter comprises at least one completely differential operational amplifier having two inputs and two outputs and at least one pair of feedback circuits connecting said outputs with respective inputs of said amplifier outside of same. The operational amplifier has no common-mode feedback circuit, whose functions are performed by said feedback circuits external to the amplifier.Type: GrantFiled: December 19, 1989Date of Patent: January 28, 1992Assignee: SGS-Thomson Microelectronics s.r.l.Inventor: Germano Nicollini
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Patent number: 5072200Abstract: A combination of passive electrical filters and active electrical filters in a series arrangement forming active passive band pass or high pass or low pass or band reject filters. The preferred embodiment includes an amplifier stage to include high input impedance. These filter combinations are free of internal electrical noise.Type: GrantFiled: November 2, 1990Date of Patent: December 10, 1991Inventor: Bela Ranky
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Patent number: 5045805Abstract: A high precision composite amplifier for use in a data acquisition subsystem of a Computerized Tomography (CT) scanner provides enhanced high speed response in terms of reduced settling time. The speed improvement is due to a novel compensation network in which a high frequency pole and a zero in the open loop response characteristic for the composite amplifier are forced to cancel despite component and temperature variations. The resulting amplifier exhibits a simple, higher speed, single pole response. An adjustable circuit is provided for adjusting the placement of the zero to assure optimum pole/zero cancellation.Type: GrantFiled: June 29, 1990Date of Patent: September 3, 1991Assignee: General Electric CompanyInventor: Paul C. Schanen
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Patent number: 4994693Abstract: A second order active filter comprises an input terminal, an output terminal, and a common terminal, a capacitive T-network comprising three capacitors and, in parallel therewith, a resistive T-network comprising three resistors, the terminals of the T-networks being connected respectively via a first amplifier to the output terminal, via a buffer to the input terminal, and to the common terminal, a potential divider between the output and common terminals, and a second amplifier having an input coupled to a tapping point of the potential divider and an output coupled via a resistor to the central junction of the capacitive T-network and via a capacitor to the central junction of the resistive T-network. In different configurations of the filter, the component coupled to the common terminal may be omitted from one of the T-networks, or from both of the networks with another potential divider coupled between the input and common terminals and a third amplifier coupling its tapping point to one of the networks.Type: GrantFiled: November 30, 1989Date of Patent: February 19, 1991Assignee: Northern Telecom LimitedInventor: Petre Popescu
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Patent number: 4984292Abstract: The present application relates to an active bandpass amplifier comprising a single stage operational amplifier, a bridged "T" network single frequency elimination filter in the negative feedback path of the amplifier and a phase shift correcting capacitor associated with the bridged "T" network single frequency elimination filter to effect a phase shift sufficient to maintain an appropriate feedback such that the amplifier is stable. The bridged "T" network single frequency elimination filter in conjunction with the circuit capacities and phase shifts in the integrated circuits introduces a phase shift which would result in the amplifier oscillating when the network is placed in the feedback path and the corrective capacitor effects a corrective phase shift to render the amplifier stable.Type: GrantFiled: September 28, 1988Date of Patent: January 8, 1991Assignee: Correpro (Canada) Inc.Inventor: Ted I. Millen
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Patent number: 4924189Abstract: A two-port switched capacitor filter network of the type comprising two input terminals (4, 6), two output terminals (8, 10) and at least three integrator circuits (12, 14, 16) connected therebetween, each integrator circuit including two inputs provided with capacitors which are switched under the control of two disjoint clock states, said integrator circuits being interconnected to constitute a sampling filter having a selected amplitude/frequency response. The two-port network includes two other integrator circuits (36, 38) whose respective inputs are fitted with capacitors switched under the control of two disjoint clock states, said other integrator circuit being interconnected with each other and with the first-mentioned integrator circuits in order to linearize the phase/frequency response of said filter.Type: GrantFiled: August 24, 1988Date of Patent: May 8, 1990Assignee: L'Etat Francais, represente par la Ministre Delegue des Postes et Telecommunications, (Centre National d'Etudes des Telecommunications)Inventors: Patrice Senn, Mohamed S. Tawfik
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Patent number: 4920325Abstract: The filter comprises four operational amplifiers in cascade, with switched capacitors in series at the input of every amplifier, with fixed capacitors in parallel to two of said amplifiers, with fixed and switched capacitors in parallel to the remaining amplifiers, and with fixed and switched capacitors in common to groups of several amplifiers in cascade. According to the invention, a path of fixed and switched capacitors in parallel connects the input of the filter to the input of the fourth amplifier, and a fixed capacitor connects the input of the filter to the input of the second amplifier.Type: GrantFiled: February 26, 1988Date of Patent: April 24, 1990Assignee: SGS-Thomson Microelectronics S.p.A.Inventors: Germano Nicollini, Daniel Senderowicz
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Patent number: 4918338Abstract: A tunable drain-biased transresistance (DBT) device for generating accurate linearly variable RC values employs first and second matched MOS transistors connected in first and second series circuits with third and fourth matched MOS transistors, respectively, across the terminals of a source of supply voltage. A differential amplifier has first and second input terminals connected to respective drain electrodes of the first and second MOS transistors and an output coupled via a feedback circuit to at least one of its input terminals. A pair of signal input terminals are connected to the gate electrodes of the first and second transistors so that said input terminals operate into a high impedance. A source of adjustable bias voltage (V.sub.B) is connected in common to the gate electrodes of the third and fourth transistors thereby to supply adjustable bias currents (I.sub.B) to the drain electrodes of the first and second transistors so as to bias these transistors into their triode regions.Type: GrantFiled: October 4, 1988Date of Patent: April 17, 1990Assignee: North American Philips CorporationInventor: Stephen L. Wong
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Patent number: 4914408Abstract: Asymmetric polyphase filer having first to fourth input terminals for applying thereto a 4-phase input signal including first to fourth signal vectors, respectively, which succeed one another in phase each time through 90.degree., first to fourth intercoupled identical filter sections, respectively, connected to the terminals, at least one of the odd and even filter sections being coupled to two output terminals, said filter sections having constant reactances.Type: GrantFiled: April 24, 1989Date of Patent: April 3, 1990Assignee: U.S. Philips CorporationInventor: Johannes O. Voorman
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Patent number: 4899069Abstract: An integrated, low-pass filter of the first order made using the switched capacitors technique utilizes advantageously a single switched capacitor and only two switches in contrast to the filters of the prior art which utilize two switched capacitors and four switches. The filter of the invention requires a smaller integration area and moreover exhibits a greater precision of its DC gain.Type: GrantFiled: December 16, 1988Date of Patent: February 6, 1990Assignee: SGS-Thomson Microelectronics s.r.l.Inventor: Germano Nicollini
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Patent number: 4888789Abstract: An audio equalization circuit for use in an AM transmission system is described which is particularly useful for compensating for the high frequency rolloff found in currently manufactured AM receivers. A single potentiometer adjustment in the feedback path of the equalization circuit allows the response in the AM receiver to be effectively and economically adjusted.Type: GrantFiled: January 14, 1985Date of Patent: December 19, 1989Inventor: Robert A. Orban
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Patent number: 4862097Abstract: A pulsating noise removal device detects a pulsating noise, controls a gate circuit for selectively permitting an audio signal to pass through in response to the detection, and removes pulsating noises from the audio signal. The device particularly includes filter circuits for extracting pulsating noises and signal components from the audio signal, respectively, and includes automatic gain control circuits responsive to respective output signals of the filter circuits to respectively control the gain of an amplifier circuit for detecting pulsating noises.Type: GrantFiled: January 19, 1988Date of Patent: August 29, 1989Assignee: Clarion, Co., Ltd.Inventors: Kiyoshi Amazawa, Akira Mori
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Patent number: 4857778Abstract: The invention relates to a microprocessor-programmable, universal active filter. The filter has an input section, an operational amplifier with two input nodes, a bandpass section, a lowpass section and control circuitry which, under clock control, periodically brings one of the inputs of the operational amplifier to within a low, d.c. offset voltage, approaching zero volts, of the other input. The output of the lowpass filter section is coupled to the input of the bandpass filter section and the lowpass section also has a feedback loop back to the bandpass section. The selectivity "Q", the gain, center frequency and the output characteristics, such as bandpass, lowpass, allpass, highpass or notch, of the filter may be selected using MOS switches under microprocessor control.Type: GrantFiled: January 28, 1988Date of Patent: August 15, 1989Assignee: Maxim Integrated ProductsInventor: Yusuf A. Hague
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Patent number: RE35379Abstract: The filter comprises at least one completely differential operational amplifier having two inputs and two outputs and at least one pair of feedback circuits connecting said outputs with respective inputs of said amplifier outside of same. The operational amplifier has no common-mode feedback circuit, whose functions are performed by said feedback circuits external to the amplifier.Type: GrantFiled: January 28, 1994Date of Patent: November 19, 1996Assignee: SGS Thomson Microelectronics S.r.l.Inventor: Germano Nicollini
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Patent number: RE35494Abstract: An integrated, low-pass filter of the first order made using the switched capacitors technique utilizes advantageously a single switched capacitor and only two switches in contrast to the filters of the prior art which utilize two switched capacitors and four switches. The filter of the invention requires a smaller integration area and moreover exhibits a greater precision of its DC gain.Type: GrantFiled: May 2, 1994Date of Patent: April 22, 1997Assignee: SGS-Thomson Microelectronics, S.r.l.Inventor: Germano Nicollini