Abstract: A predistortion system adaptively compensates for distortion introduced along one or more amplification chains of a power amplifier system. In one embodiment, the predistortion system includes a plurality of compensation circuits, each of which is coupled to, and configured to digitally predistort an input transmission signal to, a respective amplification chain of an antenna array system. Each such amplification chain has an output coupled to a respective antenna of the antenna array system. A processing unit monitors the input transmission signals to, and corresponding output signals from, each of the amplification chains on a time-shared basis, and generates updates to the compensation parameters used the corresponding compensation circuits.

Abstract: A distortion compensation apparatus for compensating for the distortion occurring in an amplifier with high precision is provided. Distortion generating devices generate a distortion of amplitude or phase on a signal to be provided for an amplifier. A signal level detecting device detects a level of the signal provided for the amplifier, and a distortion amount control system controls the amount of distortion generated by the distortion generating devices on the basis of the level detected by the signal level detecting device, and at this time, a control timing adjusting system adjusts the timing for controlling the distortion amount by a distortion amount control system (D/A converters) so that the distortion occurring in the amplifier maybe compensated sufficiently.

Abstract: A circuit that compensates for distortion of an output signal of a power amplifying circuit of a transmitting section of a base station or a terminal of a radio communication system and apparatus such as a mobile phone, and a predistorter system applicable to radio communication systems and that does not depend on a use system other than generation of envelope change due to a high-frequency input signal without addition of the distortion compensating circuit to a base band portion, the compensating circuit including a memory device where inverted distortion data of a high-frequency power amplifying device for a mobile phone are stored is driven with data obtained by detecting an envelope of a high-frequency input signal having envelope change as an address and distortion compensation of the power amplifying device is made by adjusting a variable gain device provided at a prestage of the power amplifying device.

Abstract: A method and arrangement for correcting a phase error in a linearization loop of a power amplifier, the loop comprising an I/Q modulator (10), one or more delay-causing power amplifiers (13) to be linearized, an I/Q demodulator (11) for generating I and Q feedback signals from the output signals of the amplifier (13), difference means (20, 21) of the I and Q branches for generating I and Q difference signals from the I and Q feedback signals and the I and Q input signals, the I/Q modulator and the I/Q demodulator receiving an oscillator frequency from the same local oscillator (14), and a phase shifter (17), the method comprising determination of a phase error resulting from the delay produced in the linearization loop, which determination comprises feeding excitation signals to the I and Q inputs (I IN, Q_IN) of the linearization loop, measuring the signals resulting from the excitation signals and calculating a phase error by means of the measured signals and excitation signals, and correcting the phase err

Abstract: In an input signal power dynamic range compressing circuit, an input signal is distributed by a directional coupler to a linear signal transfer path and a compressing signal generating path, and in the compressing signal generating path a compressing signal, which keeps the peak-to-average-power ratio of the input signal below a predetermined value, is generated from the input signal. The compressing signal is combined by a power combiner with the input signal having passed through the linear signal transfer path.

Abstract: A circuit for splitting poles between a first stage and a second inverting voltage-amplifier stage of an electronic circuit, comprises, in series between the output of the first stage and the output of the second stage, and in that order, a first capacitor, a second capacitor and a resistor. The circuit further comprises a voltage-divider bridge which is connected between a terminal delivering a substantially constant voltage and the output of the first stage. The output of the voltage-divider bridge is linked to the common node between the first capacitor and the second capacitor, in such a way that a first resistor of the voltage-divider bridge is connected in parallel with the first capacitor.

Abstract: The present invention relates generally to an amplifier such as that with the radio frequency (RF) spectrum having a nonlinear feedback loop to cancel out distortions in the input signal, and method therefor.

Abstract: A technique is disclosed which facilitates the layout of op amp cells, for example, two-stage op amp cells or three-stage op amp cells, to provide larger operational amplifiers. In accordance with one aspect, the op amp cells can be suitably coupled in parallel to provide a larger operational amplifier. This paralleling aspect can be facilitated by connecting the respective negative and positive inputs of a predetermined number of input gm stages together, connecting the outputs of a predetermined number of output gm stages together, and connecting a predetermined number of intermediate internal nodes between the input gm stages and the output gm stages together, without the occurrence of saturation of the internal nodes. In addition, the input and output characteristics of operational amplifier can be suitably improved.

Abstract: A complex baseband model of the power amplifier within a DSP domain is used to develop a feedback signal that would be equivalent to the optimum negative feedback used for the analog amplifier. Once the feedback signal is available, it can be processed to compensate for the effects of the group delay and for optimum loop gain, hence resulting in a broadband response with no theoretical limitations on the linearization of the amplifier.

Abstract: A bandpass amplifier for use in a communication system is described. The amplifier includes first and second first-order filters, first and second multipliers, a quantizer, and a driver. In one embodiment, the first and second first-order filters are coupled in series. The first multiplier multiplies a signal from the first first-order filter by a coefficient k1, and the second multiplier multiplies a signal from the second first-order filter by a coefficient k2. The quantizer quantizes a summation of the signals from the first and second multipliers into one of two values, thereby generating a quantized signal. The driver amplifies the quantized signal, and generating an output signal. At least one of the coefficients k1 and k2 is adjusted based on a level of the output signal.

Abstract: An operational amplifier (opamp) [74] coupled in a negative-feedback configuration [82] [84] comprising a driving opamp [76]; a linear controller [78]; and a mechanism [80] controlling the driving opamp's [76] offset. A voltage signal Vin provided by the feedback network [82][84] characterizes all errors caused by the driving opamp [76]. The controller [78] monitors this voltage and minimizes the signal-band spectral components thereof by inducing an offset in the driving opamp [76]. The offset control mechanism [80] has approximately constant gain and only little phase delay in the signal band.

Abstract: A variable gain amplifying apparatus has

Abstract: A distortion compensating device which can significantly remove residual distortion, in which a value of matching circuit 11 is set up so that the distortion generated at a gain controlling unit 9 offsets the distortion remaining in a power amplifier 12. That is, the value of the matching circuit 11 is set up so that the phase of the residual distortion included in the output of the matching circuit 11 is rendered opposite to the phase of the residual distortion included in the output of the power amplifier 12. Thus, the residual distortion included in the output of the power amplifier 12 is offset by the residual distortion included in the output of the gain controlling unit 9, thereby the residual distortion can be removed.

Abstract: A compensated three stage amplifier having high gain as well as high speed is disclosed. The amplifier comprises a NMC and NGCC compensated cascaded three stage amplifier for receiving an input signal and for providing an amplified output signal in dependence thereupon. An extra feed forward transconductance stage extending from the input port of a first gain stage to the output port of a second gain stage of the amplifier is used in order to cancel one of two non-dominant poles in the transfer function of the amplifier with the additional zero introduced by the extra signal path. This results in a transfer function for a three stage cascaded amplifier having only two poles, which is highly desirable by allowing design of such amplifiers providing stable operation at high gain as well as high speed.

Abstract: An amplifier system including a vacuum tube amplifier having an input signal terminal and an output signal terminal, wherein the vacuum tube amplifier is for amplifying an input signal supplied to the input signal terminal, a phase comparator having a first input terminal responsive to the input signal and having a second input terminal coupled to the output signal terminal of the vacuum tube amplifier, and a phase shifter having a first input terminal responsive to the input signal, a second input terminal coupled to an output terminal of the phase comparator, and an output terminal coupled to the input signal terminal of the vacuum tube amplifier.

Abstract: A feedback loop with an adjustable closed loop frequency response. The feedback loop contains adjustable pole (212, 213) and adjustable zero elements (220,221) for changing the pole and/or zero locations in the feedback loop's loop frequency response thereby changing the closed loop frequency response of the feedback loop. In one embodiment, the feedback loop is a Cartesian feedback loop suitable for use in a radio transmitter.

Abstract: A power amplifier system for use in amplifying an RF input signal exhibiting a given operating frequency within a known range of frequencies. The system includes a signal modulator that receives and modifies the input signal and provides therefrom a modified first signal. A power amplifier receives and amplifies the modified first signal. A first power detector detects the input signal and provides therefrom an average input power signal representative of the average input power thereof. A second power detector connected to the output of the amplifier provides an output average power signal representative of the average output power thereof. A controller adjusts the magnitude of said average input power signal and the magnitude of said average output power signal as a function of the operating frequency. The controller compares the adjusted said input average power signal and said adjusted output average power signal and controls said modulator in accordance therewith.

Abstract: An amplifier is disclosed including multiple integrator stages. The amplifier includes a low-frequency path from a signal input to a signal output and relatively higher-frequency bypass paths around the first integrator stage. The paths converge at a summing node. To prevent instability when the integrators are saturated by large signals, the circuit includes a saturation detector which disables the relatively low-frequency paths during such saturation conditions.

Abstract: An amplitude compensator utilized in a distortion compensating device which compensates non-linearity in amplitude and phase of an input-output characteristic of a high frequency power amplifier incorporated in a mobile phone in which the input-output amplitude characteristic of the high frequency power amplifier is fitted by a hyperbolic tangent function, and an inverse hyperbolic tangent function is obtained by using two parameters, thereby providing amplitude compensation. A voltage input-output characteristic of the power amplifier is fitted to a hyperbolic function including predetermined parameters and a logarithmic function constituted by the parameters after the fitting and a linear gain of the power amplifier is obtained. An envelope voltage of an envelope signal obtained by detection of a modulated input signal is applied to the logarithmic function to obtain an amplitude compensating value.

Abstract: One aspect of the invention is an integrated circuit (10 or 110) comprising an amplifier (11 or 111) having at least two poles in its frequency response and an output impedance compensation circuit (M1A, M2, M3, AC1 or M1A, M2, M3, M4, AC1) coupled to an output node (30) of the amplifier (11 or 111). The output impedance compensation circuit (M1A, M2, M3, AC1 or M1A, M2, M3, M4, AC1) is operable to create a feedback signal proportional to the impedance of an output load (50) coupled to the output node (30), and create a zero in the frequency response of the amplifier (11 or 111) in response to the feedback signal between the at least two poles.

Abstract: System (100) is coupled with power amplifier (106). Generation component (166) generates error signal (110) based at least in part on an input signal (144) for the system (100). The error signal (110) includes a phase component. The input signal (144) includes an envelope component. Modification component (130) modifies the phase component of the error signal (110) in response to the envelope component of the input signal to reduce variation of a phase component of the power amplifier output signal (194).

Abstract: An amplifier having an input; an output supplying an output signal, and a feedback network connected between the input and the output, and a distortion detection circuit. The feedback network includes a first and a second feedback element arranged in series and forming an intermediate node supplying an intermediate signal in phase with the output signal in absence of distortion, and in phase-opposition with the output signal in presence of distortion. The distortion detection circuit includes a phase-comparating circuit which detects the phase of the output signal and of the intermediate signal, and generates a distortion-indicative signal, when the intermediate signal is in phase opposition with respect to the output signal.

Abstract: An amplifier system including a vacuum tube amplifier having an input signal terminal and an output signal terminal, wherein the vacuum tube amplifier is for amplifying an input signal supplied to the input signal terminal, a phase comparator having a first input terminal responsive to the input signal and having a second input terminal coupled to the output signal terminal of the vacuum tube amplifier, and a phase shifter having a first input terminal responsive to the input signal, a second input terminal coupled to an output terminal of the phase comparator, and an output terminal coupled to the input signal terminal of the vacuum tube amplifier.

Abstract: The invention relates to a device for amplifying electronic signals, including: an amplifier PRA, and a plurality of feedback loops G1, G2 placed between the output and the input of the amplifier, which feedback loops are arranged so that each feedback loop has an adjustable gain and all the feedback loops jointly form an assembly having an equivalent impedance which is substantially independent of the gain settings selected. Thanks to the invention, the amplification bandwidth can be easily adjusted without adversely affecting the performance of the device in terms of noise and high cut-off frequency.

Abstract: A distortion compensation apparatus for compensating for the distortion occurring in an amplifier with high precision is provided. Distortion generating devices generate a distortion of amplitude or phase on a signal to be provided for an amplifier. A signal level detecting device detects a level of the signal provided for the amplifier, and a distortion amount control system controls the amount of distortion generated by the distortion generating devices on the basis of the level detected by the signal level detecting device, and at this time, a control timing adjusting system adjusts the timing for controlling the distortion amount by a distortion amount control system (D/A converters) so that the distortion occurring in the amplifier maybe compensated sufficiently.

Abstract: Accuracy of correction of offset drift with temperature and noise are corrected in a high voltage, high current amplifier is improved by thermal isolation and/or temperature regulation of another amplifier having greater gain and connected to a different power supply in a closed loop feedback servo system. A clamping network connected to the higher gain amplifier to avoid hard saturation due to transient feedback signals from a reactive load, especially an inductive load, also prevents hard saturation of the high voltage, high current amplifier. An adjustable feedback circuit connected to the higher gain amplifier allows adjustment to obtain critical damping of a second order system and faster response to achieve proportionality of output current to input voltage with an accuracy of very few parts per million error and with minimum settling time.

Abstract: Power amplifier circuit incorporating a negative feedback circuit for a transmitter and phase control method therefor. An I-component test signal and an I-component baseband feedback signal are added for generating an I-component summing signal. A Q-component test signal and a Q-component baseband feedback signal are added for generating a Q-component summing signal. A carrier is orthogonally modulated with the I- and Q-component summing signals. A part of the modulated signal is orthogonally demodulated with the carrier, whereby I-component baseband feedback signal and Q-component baseband feedback signal are outputted. Phase of the carrier is changed in accordance with a phase control signal for holding the phase of the carrier at a time when the detected state of one of the i- and Q-component summing signals as selected meets predetermined condition.

Abstract: A bandpass amplifier for use in a communication system is described. The amplifier includes first and second first-order filters, first and second multipliers, a quantizer, and a driver. In one embodiment, the first and second first-order filters are coupled in series. The first multiplier multiplies a signal from the first first-order filter by a coefficient k1, and the second multiplier multiplies a signal from the second first-order filter by a coefficient k2. The quantizer quantizes a summation of the signals from the first and second multipliers into one of two values, thereby generating a quantized signal. The driver amplifies the quantized signal, and generating an output signal. At least one of the coefficients k1 and k2 is adjusted based on a level of the output signal.

Abstract: When using an operational amplifier having a small gain-band width product, in order to obtain a circuit having deep notch characteristics, a biquad filter includes first and second stages having inverse amplifiers and third and fourth stages having inverse integrators. Replacing a feed back resistor with an impedance element provides compensation. The compensating impedance element is a reactance, such as an inductor or capacitor connected to the feed back resistor.

Abstract: A tunable inductor circuit and phase tuning circuit utilizing a tunable inductor circuit for dynamically controlling signal phase delay in RF/Microwave Circuits and related applications. The tunable inductor includes an inductor and a voltage variable capacitor connected to each other. The tunable inductor and voltage variable capacitor can be connected to each other in parallel or in series. The phase tuning circuit includes at least one tunable inductor circuit and at least one voltage variable capacitor coupled to the at least one tunable inductor circuit, wherein the at least one tunable inductor circuit and the voltage variable capacitor are responsive to control signals to alter a tuning characteristic of the phase tuning circuit.

Abstract: A bandwidth enhancement method by adding a peaking capacitor to a transimpedance amplifier for creating peaking effect is to add a peaking capacitor to a transimpedance amplifier for obtaining an extra pole that can alter circuit phase and enhance bandwidth of the transimpedance amplifier without changing the framework and DC gain of the original amplifier circuit.

Abstract: An amplifier having an input; an output supplying an output signal, and a feedback network connected between the input and the output, and a distortion detection circuit. The feedback network includes a first and a second feedback element arranged in series and forming an intermediate node supplying an intermediate signal in phase with the output signal in absence of distortion, and in phase-opposition with the output signal in presence of distortion. The distortion detection circuit includes a phase-comparating circuit which detects the phase of the output signal and of the intermediate signal, and generates a distortion-indicative signal, when the intermediate signal is in phase opposition with respect to the output signal.

Abstract: A signal processing circuit and method for processing an input signal are described. The circuit includes a frequency selective network, an amplification stage, and at least one continuous-time feedback path from the output of the amplification stage to the frequency selective network. The amplification stage includes a switching amplifier and an analog amplifier. Switching circuitry alternately enables the switching and analog amplifiers for processing of the input signal.

Abstract: A linear power amplifier arrangement is used for providing a selectable amount of amplification to a radio frequency signal to be amplified. The arrangement comprises a first parallel amplifier branch and a second parallel amplifier branch and means for conducting the radio frequency signal to be amplified selectably to one of the parallel amplifier branches. Additionally it comprises in the first parallel amplifier branch a series connection of a predistorter and a nonlinear amplifier, where said predistorter is arranged to compensate for the nonlinearity of said nonlinear amplifier.

Abstract: The present invention relates to a system and method for compensating IC parameters. According to an embodiment of the present invention, a die of an IC wafer is coupled with a compensation circuit that classifies the die into various types. Examples of types include fast, typical, and slow. The assigned type may be used in a special oscillator that compensates for variations from a die to a predetermined criteria. According to an embodiment of the present invention, a slow die directs a signal that moves through a relatively short path, a fast die directs a signal that moves through a relatively long path, and a typical die directs a signal that moves through a relatively medium length path in the compensation circuit. Accordingly, each die on a wafer may be coupled with a compensation circuit such that the compensation circuit selects a path of a circuit that adjusts the frequency produced by the dies to produce a batch of ICs that would meet the predetermined criteria for the vast majority of the dies.

Abstract: A 3-terminal operational filter circuit is presented that can be used to construct various types of active filters. The filter circuit can be configured to provide 2nd order low pass and band-pass frequency responses by coupling three resistors to the three filter terminals. Similarly, the filter circuit can be configured to provide 2nd order band-pass and high pass frequency responses by coupling two resistors and a capacitor to the three filter terminals. Furthermore, a plurality of filter circuits can be cascaded to construct various types of higher order filters. The filter circuit can be manufactured to operate within a selected range of center frequencies by selecting particular values for the internal filter capacitance and resistance. Users can then select a particular center frequency, quality factor, and gain of the filter circuit by selecting particular values for the circuit elements to be coupled to the three terminals.

Abstract: An amplifier system includes an input circuit loop and an output circuit loop coupled to a balanced amplifier assembly. The balanced amplifier assembly provides both a nonlinear distortion signal component and a corrective precursor signal component for enhanced and virtually complete cancellation of the nonlinear distortion signal component. A phase shifter facilitates phase shifting in a feedback signal path between the output circuit loop and the input circuit loop to form a corrective signal component from the corrective precursor signal.

Abstract: A filter circuit is provided that provides an input impedance arrangement with a high impedance value, which can be fabricated on a semiconductor body with a high accuracy and with a minimal semiconductor area being required. The input impedance arrangement comprises at least one T network having at least three impedance branches, of which a first impedance branch is connected to the filter input, a second impedance branch is connected to the amplifier input and a third impedance branch is connected to a circuit point for draining a current from the filter input.

Abstract: The present invention addresses the need for an apparatus and method for controlling the load of a PA, to improve PA efficiency in linear transmitters with isolator elimination (IE) circuitry, that does not require the use of high frequency RF circuitry. The present invention provides a PA load controller (130, 131) that improves the efficiency of a PA (116) by adjusting the PA load using an AGC signal (134), a level set adjustment signal (132), and a signal strength indicator (135), these three signals are readily obtained from continuous gain and phase adjustment circuitry (e.g., 102). The load controller determines a phase of the PA load that minimizes the AGC signal and a phase of the PA load that maximizes the level set adjustment signal. From these determinations, the PA load controller determines a phase of the PA load that improves the efficiency of the PA and adjusts the PA load phase accordingly.

Abstract: A signal processing circuit is described including a frequency selective network in a feedback loop. An analog-to-analog converter in the feedback loop is coupled to the frequency selective network. A continuous-time feedback path provides feedback from the output terminal of the analog-to-analog converter to the frequency selective network.

Abstract: In this invention an integrated operational amplifier is calibrated to optimize phase margin. The calibration is done to correct changes caused by operating temp and supply voltages as well as process variations and aging that can affect the stability of the amplifier. A calibration circuit measures the response of the operational amplifier to a pulse input and controls a feedback impedance to produce an optimized phase margin. The output response to the pulse input is measured at two different times, at a first time close to the transition capturing the peak overshoot from an under damped amplifier and at second time later than the first measurement when the distortions from the under damped ringing have diminished. A quantizer circuit compares the two measure voltages and provides an input to control logic which selects the amount of reactance in the feedback of the operational amplifier.

Abstract: A signal processing circuit and method for processing an input signal are described. The circuit includes a frequency selective network, an amplification stage, and at least one continuous-time feedback path from the output of the amplification stage to the frequency selective network. The amplification stage includes a switching amplifier and an analog amplifier. Switching circuitry alternately enables the switching and analog amplifiers for processing of the input signal.

Abstract: A three stage amplifier is disclosed provided with a novel frequency compensation technique. Only a single feedback loop with a single compensation capacitance is provided. Instead of a conventional nested compensation technique, damping factor control is provided by means of a fourth gain stage in order to stabilize the amplifier. The resulting amplifier is particularly useful to drive large capacitive loads for low-voltage low-power applications.

Abstract: An amplifier is provided for audio or instrumentation applications which exhibits radically improved performance over existing amplifiers of comparable cost. In a preferred embodiment, the amplifier comprises two operational amplifiers (A1, A2) connected in cascade, where feedback elements (Cf2, Rf2) are connected across the second op amp (A2) to cause an intermediate voltage signal (Z) to be substantially advanced in phase. In this embodiment, a capacitor (Cf1) is also connected across the first op amp (A1), and an outer DC loop is provided with damping circuitry (Cf3) to reduce the closed loop gain at high frequencies, stabilizing the combination. The composite amplifier has performance far exceeding a conventional stand-along op amp and is very cheap to construct.

Abstract: A power amplifier system is presented for amplifying an RF input signal. The system includes a vector modulator for receiving and modifying an input signal and providing therefrom a modified signal. The system also includes at least one power amplifier the operation of which is monitored and the vector modulator is controlled in accordance with the monitoring.

Abstract: A method and apparatus reduce the out-of-band frequency components of an RF amplified signal, preferably a CDMA signal, which has a carrier frequency which is not known in advance. The apparatus and method feature locating the frequency of the incoming signal by examining an RF output signal having both in-band frequency components and out-of-band frequency components. Typically the output signal is generated using a high-power, Class A/B amplifier. Once the frequency of the carrier has been determined, the out-of-band components are used to generate control signals which, in, for example, a feedback or feedforward circuitry, reduce the energy of the out-of-band signals and thereby provide a more linear amplifier transfer function.

Abstract: This invention relates to high power linear amplifiers. A high power linear amplifier is disclosed for communications such as CDMA communication systems. Linear amplifiers as used in communication systems exhibit a linear characteristic where the amplifiers output power increases relative to an input power. After a certain input level, known as a gain saturation point, the amplifier then exhibits non-linear characteristics; the output power increases relatively little with respect to power input. This non-linear region is also known as the saturation region or the gain compression region.

Abstract: A tuning circuit which has a wide tuning bandwidth. The tuning bandwidth of the tuning frequency can be easily changed. The tuning circuit 1 is composed of two cascade-connected tuning amplifier sections 2 and 3. Each of the sections 2 and 3 is provided with cascade-connected phase-shifting circuits 10C and 30C, a voltage dividing circuit 60, and an adding circuit composed of a feedback resistor 70 and an input resistor 74. Prescribed tuning operation is performed by shifting the phase of a prescribed frequency by 360.degree. by means of the phase shifting circuits 10C and 30C and setting the open loop gain of a feedback loop at less than 1 when the output of the voltage dividing circuit 60 is feedback. The resistance ratio between the feedback resistor 70 and input resistor 74 of each tuning amplifier section is adjusted in order that the maximum damping of each tuning amplifier section becomes smaller and the tuning bandwidth of each amplifier section becomes wider.

Abstract: A circuit arrangement that reduces selected intermodulation. The circuit arrangement includes a signal amplifier coupled to a bandpass filter via an electrical path. Signal energy outside the passband is reflected back into the amplifier and causes intermodulation. The electrical path is constructed with a length that reduces intermodulation, where the length is an odd multiple of one-fourth the wavelength of a predetermined frequency in the passband. The length of the electrical path reduces intermodulation because certain signals reflected by the bandpass filter are approximately 180.degree., or an odd multiple thereof, out of phase. Energy of problematic signals that are near the edge of the passband or in the stopband is reduced, such as third order intermodulation product and pairs of signals that produce third order intermodulation products.

Abstract: An apparatus and method to obtain a high Q, narrowband active filter with high gain suitable for an integrated circuit implementation. The high Q is achieved via active feedback with an amplitude control loop. The frequency control of the active filter is achieved by means of a frequency locked loop. Both control loops compare the thermal noise of the active filter itself to voltage and frequency references to achieve the stable operating point. Control loops are normally slow relative to the transmitted data, hence avoiding the data altering the operating point of the filter.