Abstract: A high frequency amplifier is provided with: an input terminal receiving a high frequency signal; an output terminal; a three-terminal active element having a first terminal connected with the input terminal and a second terminal connected with the output terminal; a transmission line; and a capacitive structure. The three-terminal active element outputs an output signal from the output terminal in response to the high frequency signal. The transmission line and the capacitive structure are connected in series between the first and output terminals, and operate together as a series resonance circuit. The transmission line functions as an open stub at a series resonance frequency of the series resonance circuit.

Abstract: System for pulse-width-modulated class D audio amplifiers. In one preferred embodiment an adder is described to generate a difference signal responsive to an input signal and a feedback signal, a pulse-width-modulator coupled to the adder to compare the difference signal to a reference signal and produce a pulse-width-modulated signal based on the comparing, a filter coupled to an output of the pulse-width-modulator, and a loop filter having a first input coupled to the output of the filter and a second input coupled to the input of the filter, the loop filter to generate a feedback signal by applying transfer functions to signals at its inputs. The loop transfer function of the amplifier is minimum aliasing error transfer function. The minimum aliasing error properties provide low distortion and taking the feedback from the output of the filter reduces high frequency output impedance.

Abstract: An electronic signal processor for processing signals includes a complex first filter, one or more gain stages and a second filter. The first filter is characterized by a frequency response curve that includes multiple corner frequencies, with some corner frequencies being user selectable. The first filter also has at least two user-preset gain levels which may be alternately selected by a switch. Lower frequency signals are processed by the first filter with at least 12 db/octave slope, and preferably with 18 db/octave slope to minimize intermodulation distortion products by subsequent amplification in the gain stages. A second filter provides further filtering and amplitude control. The signal processor is particularly suited for processing audio frequency signals.

Abstract: A receiver circuit includes an attenuator that receives a received signal and attenuates the received signal, a DC level shifter that shifts a DC level of an attenuated signal from the attenuator, an amplifier section that has frequency characteristics of a band-pass filter and amplifies a signal from the DC level shifter that has been shifted with respect to the DC level, and a control circuit that controls an attenuation of the attenuator based on a signal output from the amplifier section. The control circuit controls the attenuation of the attenuator by changing filter characteristics of the attenuator corresponding to an amplitude of the signal output from the amplifier section so that the signal output from the amplifier section has a constant amplitude even when an amplitude of the received signal has changed.

Abstract: Embodiments related to resistive feedback amplifiers are presented herein.

Abstract: An amplifier, in particular for RF-applications, comprises a circuit board (2), at least one amplifier stage with at least one transistor package (8) arranged on the circuit board (2), and a feedback path (12) around the at least one transistor package (8), said feedback path (12) comprising a feedback element (15) with at least one capactive (C) element for blocking the flow of direct current through the feedback path (12) and preferably further comprising at least one inductive (L) and/or resistive element (R). In order to reduce negative effects on the performance of the amplifier due to long printed feedback lines, the feedback path (12) in an amplifier according to the invention is formed of a feedback bridge (9) comprising two feedback lines (13, 14) extending out of the plane of the circuit board (2) from two contact flags (10, 11) of the transistor package (8), and the feedback element (15) bridging over the transistor package (8) between the two feedback lines (13, 14).

Abstract: A variable frequency amplifier suffering less deterioration of strain characteristic and capable of operating at plural frequencies is disclosed. In one aspect, a changeable amplifier comprises an amplifying element, a changeable matching circuit disposed at an input side of the amplifying element and including a first variable capacity element connected in series with a signal conductor and a second variable capacity element connected in parallel with the signal conductor, and a control circuit for controlling the changeable matching circuit. Based on a feedback signal, the control circuit applies DC bias voltages to the first variable capacity element and the second variable capacity element of the changeable matching circuit and also applies thereto a correction signal.

Abstract: The present invention relates to a power amplifier for amplifying an electronic input signal (51) and a multi-band capable frontend with such power amplifier. The power amplifier comprises an amplifier transistor stage (1) having an input (52) and an output (53) and a feedback loop (4) placed between the output (53) and the input (52) of the amplifier transistor stage (1). The feedback loop (4) comprises a capacitor (41) and a resistive element (44) in a RF path and an inductive element (42) in a DC feed path, wherein said resistive element comprises a feedback transistor (45) arranged as variable resistor within the feedback loop, and a bias control circuit (46).

Abstract: A transistor amplifier circuit has a current to current feedback transformer for neutralization of feedback capacitance and setting the input impedance of the amplifier. IM3 cancellation is implemented by out-of-band terminations at the input, which does not depend on the loading of the output of the amplifier. The IM3 cancellation contributes better linearity, while the capacitance neutralization contributes high and stable gain. These features are more orthogonal than other prior art techniques in terms of gain and linearity over a wide dynamic range. Hence there is less of a trade-off between the desirable properties of high gain and good linearity. Notably they can be implemented to have good efficiency and high levels of integration, which are important for many applications such as wireless transceivers for portable devices or consumer equipment. The amplifier can be a single ended or a differential common emitter amplifier.

Abstract: This invention relates to a low noise amplifier, used in radio frequency integrated circuit design, especially low noise amplifiers for ultra broad-band wireless communication, comprising at least a transistor of the core circuit of a low noise amplifier structure, a transformer that is implemented on the chip, in order to form a dual feedback amplifier, that is, an amplifier structure comprising an inductive feedback and a capacitive feedback, wherein the capacitive feedback is used for the low and medium frequency range, while the inductive feedback is used for the high frequency range. By assembling an amplifier circuit with these two feedback paths, it is possible to provide a broadband and good impedance matching at the signal input end of the circuit.

Abstract: Embodiments related to resistive feedback amplifiers are presented herein.

Abstract: An amplifier circuit amplifies a signal inputted from an input terminal. A first feedback circuit is placed across an emitter of a bipolar transistor and an input of the amplifier circuit. A second feedback circuit is placed across the input and an output of the amplifier circuit for feeding the output of the amplifier circuit back to the input of the amplifier circuit. A phase change amount in the feedback circuit is determined by the values of an inductor and a capacitor. The values of these elements are selected so that a phase of a signal in which fundamental waves included in two feedback signals are combined and a phase of a signal in which second harmonics included in the two feedback signals are combined are shifted by approximately 180 degrees from a phase of a fundamental wave of an input signal.

Abstract: An operational amplifier is described. The operational amplifier includes a first stage, a second stage, a third stage, and a fourth stage. The amplifier includes a nested transconductance-capacitance compensation configuration. The third stage includes class AB control mechanism. The fourth stage includes a class AB output stage.

Abstract: The invention relates to a feedback or feedforward type variable gain wideband amplifier. The variable gain wideband amplifier includes a feedback-type inversion amplifier circuit 310 for amplifying input Vin, a feedback-type non-inversion amplifier circuit 320 for amplifying input Vin, a power source circuit 330 for controlling the gain of the non-inversion amplifier circuit 320 and a load circuit 340 connected between a junction of output terminals of the inversion and non-inversion amplifier circuits 310 and 320 and power voltage potential VDD to control the gain of the amplifier circuits 310 and 320. The variable gain wideband amplifier of the invention is feedforward type, and outputs signals from the inversion and non-inversion amplifier circuits 310 and 320 via a single output terminal in order to attenuate third order intermodulation frequency IM3 generated from the amplifier circuits 310 and 320. Then, predetermined frequencies f1 and f2 included in the input signal are amplified.

Abstract: A frequency compensation device for providing added compensation to an operational amplifier, such as a bipolar or MOS rail-to-rail output operational amplifier, when the output device of the operational amplifier is in saturation. The device comprises a detector circuit for detecting those conditions which can cause the output device to go into saturation. When saturation is detected, an auxiliary frequency compensation device provides added frequency. Thereby, in a normal mode of operation, the op-amp is not overcompensated. Yet, when an output device becomes saturated, the auxiliary compensation is added to improve stability and prevent the op-amp from becoming oscillatory.

Abstract: The two output currents (INP, IN) which are produced by a current source digital/analog converter (DAC) are supplied to the two halves of a symmetrical transimpedance amplifier. The input current (INP, IN) is supplied to a first stage, which is formed by a first transistor (N2), and a potential at the output of the first stage is supplied to a second stage, which is formed by a second transistor (N3), and the output voltage (VOUT, VOUTP) is formed by a potential at the output of the second stage. The output of the second stage is coupled to the output of the first stage through a Miller capacitor (Cm). The output of the transimpedance amplifier is coupled to its input by means of a connecting line which contains a feedback resistor (Rf).

Abstract: A signal is applied to the body of a MOSFET to enhance the transconductance of the MOSFET. The signal applied to the body of the MOSFET has essentially the same waveform as an input signal supplied to the gate of the MOSFET, and is shifted by approximately 180 degrees with respect to the input signal. The signal applied to the body of the MOSFET may be provided by a phase-adjusting feedback circuit that generates the signal from a signal representing the output of the MOSFET.

Abstract: A power amplifier includes larger size transistors to provide higher power gain at lower frequencies. Transistors of transistor unit cells include a horseshoe-shaped emitter and a strip-shaped base to increase gain. Transistors are combined at a first level to form transistor arrays, which are combined with bonding wires at a second level to an output micro strip transmission line. A Vbe referenced bias circuit may include a smart function to lower quiescent current.

Abstract: A multiple-stage operational amplifier including a gain stage for amplifying an input signal and implementing a dominant pole producing a frequency response having a gain roll-off with frequency and a unity gain frequency. An intermediate stage is coupled to an output of the gain stage and has a high input impedance and a low output impedance. A high gain amplifier configured as a low gain output stage using resistive feedback and coupled to an output of the intermediate stage drives an output of the operational amplifier and implements a dominant pole at a frequency substantially higher than the unity gain frequency implemented by the dominant pole implemented the gain stage.

Abstract: The present invention provides an amplifier for amplifying a high-frequency signal and outputting an amplified signal. The amplifier includes: an amplification element which is a bipolar transistor or a field-effect transistor; and an inductor connected between a base and a collector or between a gate and a drain of the amplification element. The inductance of the inductor is chosen so that, within a predetermined frequency range, a parallel resonance occurs with a parasitic capacitor of the amplification element and an intrinsic capacitor of the amplification element, the intrinsic capacitor being a base-collector capacitance or a gate-drain capacitance.

Abstract: A separation circuit part is used to separate an amplified signal path from a feedback signal path. An amplifier circuit part comprises a resistor-loaded common-source FET, a level adjustment diode and a source-follower circuit. The separation circuit part comprises a source-follower circuit, an output part of which is connected to a feedback circuit part comprising a resistor, thereby forming a feedback signal path to an input terminal of the amplifier circuit part. The signal separation circuit is used to separate the amplified signal path from the feedback signal path, thereby reducing the loads of the signal paths. In this way, the loads of the amplified signal and feedback signal paths are reduced.

Abstract: Stability compensation for an amplifier with adjustable gain is provided via adjustable capacitance coupled to an input of a gain element within the amplifier. Gain of the amplifier is adjusted by an adjustable resistance coupled between the input and output of the gain element. The adjustable capacitance and the adjustable resistance determine the frequency of a dominant pole of the amplifier.

Abstract: RF phase distortion circuits and methods for controllably phase distorting an RF signal based on amplitude of the RF signal. An MOS device is provided having a body of a first conductivity type and at least one region of a second conductivity type in the body, with a conductive layer over at least part of the body and the region of the second conductivity type and insulated therefrom. The MOS device may be coupled into a phase distortion circuit individually or in back-to-back pairs and biased to invert the body under the conductive layer for small signal amplitudes and not for large signal amplitudes, or to not invert the body under the conductive layer for small signal amplitudes and to invert the body under the conductive layer for large signal amplitudes. Various embodiments are disclosed.

Abstract: A dual feedback topology imparts stability to a multistage linear amplifier, particularly by improving overall amplifier phase margin at higher signal frequencies. With dual feedback, an inner feedback loop is closed around the first amplifier stage, which stage is configured as a current feedback amplifier. A second feedback loop is closed around the overall multistage amplifier. With a current feedback amplifier as the initial stage, the two feedback signals are current-mode signals and thus add to form the combined feedback signal. The frequency responses of the inner and outer feedback loops may be tailored for flat frequency response, or, where desired, may be adjusted to compensate or otherwise flatten overall amplifier frequency response.

Abstract: An Ahuja compensation circuit includes a feedback loop with a high swing cascode biasing circuit. The high swing cascode biasing circuit includes a frequency boosting circuit. The frequency response of the high swing cascode biasing circuit and the Ahuja compensation circuit are improved by the frequency boosting circuit.

Abstract: An amplifier including an input circuit tuned to the frequency to be amplified and receiving as an input the signal to be amplified, a first transistor connected in common base, the emitter of which is coupled to the input circuit and the collector of which provides the output signal of the amplifier, and a feedback circuit feeding back to the base of the transistor a fraction of the output voltage. The feedback circuit includes a capacitive bridge and a second transistor. The input circuit can be used in a first stage of the amplifier or of a mixer.

Abstract: A method for adjusting a phase angle (?) of a phase modifier (25) of a transmitting device which includes a quadrature modulator (3), a power amplifier (9), a quadrature demodulator (19) and differential amplifiers (26, 27). The power amplifier (9) is linearized via the feedback loop (16) according to the Cartesian feedback method. The phase modifier (25) supplies an oscillator signal to the quadrature demodulator (19), which signal is shifted by the phase angle (?) to be adjusted with regard to the oscillator signal that is supplied to the quadrature modulator (3). An input signal with a constant inphase component (I) and a constant quadrature phase component (Q) is applied during each transmission burst in the instance of a closed feedback loop, and the quadrature component (VQM) and/or the inphase component (VIM) is measured at a measuring point (53, 61) located behind the output of the differential amplifiers (26, 27).

Abstract: A low noise amplifier (LNA) for amplifying an input signal communicated over a transmission line having an impedance. The LNA includes a current sensing amplifier having an input to connect to the transmission line. The current sensing amplifier has an input impedance that matches the transmission line impedance. The current sensing amplifier amplifies the input signal to generate a first output signal. A voltage sensing amplifier receives the input signal and generates a second output signal. A combiner combines the first output signal and the second output signal to generate an LNA output signal.

Abstract: A non-linear distortion compensation circuit and method automatically sets to an optimal value a phase shift of a variable phase shifter and an attenuation of an attenuator according to a transmission frequency, in a non-linear distortion extractor for extracting a non-linear distortion component generated during non-linear high-power amplification. A variable phase shifter shifts adjusts a phase of a signal determined by quadrature modulating the baseband signal. A high-power amplifier non-linearly high-power amplifies the quadrature-modulated signal. An attenuator attenuates the amplified signal by a gain equal to that of the high-power amplifier. A subtracter extracts non-linear distortion generated during the non-linear high-power amplification by subtracting the phase-shifted quadrature-modulated signal from an output of the attenuator. A control circuit automatically adjusts a phase shiftof the variable phase shifter and an attenuation of the attenuator according to a transmission frequency.

Abstract: In a receiver, provision is made of a tuneable switchable bandpass filter comprising a primary resonant circuit and a first secondary resonant circuit. A second secondary resonant circuit can be switched into a part of the first primary resonant circuit, thereby producing a second primary resonant circuit. By virtue of the embodiment of the primary resonant circuit, the bandpass filter is switchable in terms of frequency range with little outlay on circuitry and, on account of the individual embodiment of a first and second secondary resonant circuit with individual coupling elements, can be optimized with regard to a constant amplitude response.

Abstract: Second-order harmonic tuning of an active device, such as a transistor used in a radio frequency (RF) power amplifier circuit, is accomplished by positioning a quarter-wavelength stub along a transmission line coupled to an output of the device, such that the output is presented with a desired impedance for the second harmonic.

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: A method to increase the bandwidth of a transimpedance amplifier using capactive feedback. The resultant amplifier maintains wide bandwidth, high linearity, low noise, and low input impedance independent of component variations. These characteristics greatly facilitate the economical measurement of small currents such as those arising from photodiodes and biological preparations.

Abstract: An amplifier with Miller-effect frequency compensation in which the Miller feedback capacitor is connected to an internal terminal of the amplifier having a low impedance, and shunt compensation circuitry is connected to an intermediate signal terminal that drives the output amplifier stage. The compensation circuitry, which includes serially coupled capacitive and resistive circuit elements, introduces a high frequency zero to cancel one of the high frequency complex poles introduced by the Miller feedback capacitor connection.

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 circuit (10) having multiple poles within an active frequency range employs a movable zero (66) to maintain stability in the circuit (10) under variable load conditions. A pole (62) created by a frequency compensation element (14) maintains a fixed frequency within the active frequency range of the circuit (10). In addition, a variable load impedance (36) coupled to the circuit (10) generates a load pole (64) within the active frequency range of the circuit (10) that changes frequency over time. As the load pole (64) changes frequency, the frequency of the movable zero (66) is adjusted to achieve an enhanced stability condition within the circuit (10). In one embodiment, the frequency of the movable zero (66) tracks the frequency of the load pole (64) as the load impedance (36) changes.

Abstract: A low power analog equalizer is disclosed that provides up to twenty decibels (20 dB) of alternating current gain in a single stage of analog signal equalization. The analog equalizer comprises an operational amplifier coupled to two half circuits. Each half circuit comprises an impedance network capable of receiving an analog input voltage and generating a current signal that is inversely proportional to frequency, a variable resistor capable of adjusting the gain of the operational amplifier, and a transistor and an amplifier coupled in a cascode configuration to create a low impedance node at the output of the impedance network. The analog equalizer is fabricated with 0.18 micron CMOS technology and operates at 1.8 volts.

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: Realizing a stabilized gain slope without increasing circuit scale or entailing extra time or care for correcting impedance. A resonant circuit that is made up of a capacitor and an inductor is provided in an output stage outside a feedback loop for realizing peaking at a particular frequency and for realizing a gain slope having a desired slope of, for example, 1 dB or more.

Abstract: A transistor amplifier utilizes a dual loop feedback control circuit and an impedance matching circuit to provide improved linear and return loss performance characteristics. The transistor amplifier comprises a transistor for linearly amplifying an input signal, the transistor having a base, a collector and an emitter, the base having an input impedance, the collector having an output impedance. The dual loop feedback control circuit comprising a series feedback resistor electrically coupled between the emitter and a ground potential and a shunt feedback resistor electrically coupled between the collector and base. The dual loop feedback control circuit converts the input impedance to a conjugate of a source resistance and the output impedance to optimum load impedance.

Abstract: RF amplifiers used in communications systems exhibit backward intermodulation caused by non-linear amplification. Backward intermodulation of the transmit signal and an external signal, which reaches the output of the amplifier through the antenna, results in an unwanted third-order intermodulation product that potentially interferes with the proper reception of the receive signal. The receive sensitivity of the communications system is adversely affected by this unwanted third-order intermodulation product. By mixing a second-order intermodulation component, caused by the same backward intermodulation, with the transmit signal, a compensation signal is created allowing the cancellation of the unwanted third-order intermodulation component.

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: A feedback circuit is connected between a drain electrode and a gate electrode of an FET. The feedback circuit is constituted by a series connection of a feedback amount adjusting resistor and an LC series resonance circuit. The LC series resonance circuit is constituted by a series connection of a capacitor and an inductor. The capacitance of the capacitor and the inductance of the inductor are set such that the LC series resonance circuit enters a short-circuited state with respect to an m-th harmonic by resonating at the frequency of the m-th harmonic, and the LC series resonance circuit enters an opened state with respect to a fundamental wave.

Abstract: Resonator comprising first and second balanced integrators (I1, I2) each composed with a balanced amplifier and having a non-inverting (in+) and an inverting (in−) input terminal, as well as a non-inverting (out+) and an inverting (out−) output terminal. First and second coupling circuits (Y1, Y2) are interconnected between the non-inverting output terminal (out+) of the first integrator (I1) and the non-inverting input terminal (in+) of the second integrator (I2) and between the inverting output terminal (out−) of the first integrator (I1) and the inverting input terminal (in-) of the second integrator (I2) respectively.

Abstract: Realizing a stabilized gain slope without increasing circuit scale or entailing extra time or care for correcting impedance. A resonant circuit that is made up of a capacitor and an inductor is provided in an output stage outside a feedback loop for realizing peaking at a particular frequency and for realizing a gain slope having a desired slope of, for example, 1 dB or more.

Abstract: This invention relates to an electronic circuit (predistortion type linearizer) for linearizing the nonlinear responses of amplifiers, to achieve low distortion, wide-dynamic range amplification particularly suitable for cellular handsets application.

Abstract: A feedback type variable gain amplifier of the present invention is provided with a first inductor and a first field effect transistor connected in series across a power-supply potential terminal and a ground potential terminal, the one end of the first inductor connecting to the power-supply potential terminal, the one end of the first field effect transistor connecting to the ground potential terminal, the gate of the first field effect transistor being used as a signal input terminal, and the other end of the first field effect transistor being used as a signal output terminal, a second inductor, a second field effect transistor and a capacitor connected in series between the drain and the gate of the first field effect transistor, and, a resistor connected between the drain and the gate of said second field effect transistor.

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: A feedback circuit is connected between a drain electrode and a gate electrode of an FET. The feedback circuit is constituted by a series connection of a feedback amount adjusting resistor and an LC series resonance circuit. The LC series resonance circuit is constituted by a series connection of a capacitor and an inductor. The capacitance of the capacitor and the inductance of the inductor are set such that the LC series resonance circuit enters a short-circuited state with respect to an m-th harmonic by resonating at the frequency of the m-th harmonic, and the LC series resonance circuit enters an opened state with respect to a fundamental wave.

Abstract: An RF probe for a plasma chamber picks up current and voltage samples of the RF power applied to an RF plasma chamber, and the RF voltage and current waveforms are supplied to respective mixers. A local oscillator supplies both mixers with a local oscillator signal at the RF frequency plus or minus about 15 KHz, so that the mixers provide respective voltage and current baseband signals that are frequency shifted down to the audio range. The phase relation to the applied current and voltage is preserved in the baseband signals. These baseband signals are then applied to a stereo, two-channel A/D converter, which provides a serial digital signal to a digital signal processor or DSP. A local oscillator interface brings a feedback signal from the DSP to the local oscillator. The DSP can be suitably programmed to obtain complex Fast Fourier Transforms of the voltage and current baseband samples.