Abstract: A system and method for compensating an amplifier apparatus for low frequency and/or DC components of an externally applied input signal as well as for any voltage offsets contributed by the amplifier circuitry. Band-limited servo feedback is applied to predetermined nodes in the forward gain path to null out unwanted signal components, leaving a residual signal that, when amplified, will be centered around ground, so that the full dynamic range of the amplifier system may be utilized. Consequently, the signal-to-noise ratio available at the output of the amplifier system will be maximized. The servo compensation may either operate in continuous time, or it may be held constant once a suitable level of compensation has been established, or it may be adjusted from time to time to accommodate slow variations of the average DC component of the input signal.

Abstract: A RFPA (radio frequency power amplifier) circuit (150) which includes a RFPA (101), a supply voltage source (104), means (155) for applying to the RFPA a gain control bias voltage and a feedback control loop (156) for adjusting a voltage applied to the RFPA, the feedback control loop including a sampler (107) for sampling an output of the RFPA, a RF detector (109) for detecting a level of RF power sampled by the sampler, a comparator (115) for comparing an output signal from the RF detector with a reference signal, an integrator (117) for integrating an output signal of the comparator and a voltage regulator (151) having a first input from the integrator and a second input from the supply voltage source and an output connected to the RFPA, the regulator being operable to apply to the RFPA a supply voltage adjusted in response to an input signal from the integrator.

Abstract: A filter comprising an off-chip capacitor is described. The off-chip capacitor may be coupled to a circuit bonding pad. The output terminal of an amplifier may be coupled to the circuit bonding pad by a plurality of conductors insulated from one another over at least a portion between the output terminal and the circuit bonding pad.

Abstract: A method and apparatus is used to provide DC stabilization and noise reduction in a multistage power amplifier. The invention uses various feedback techniques to stabilize DC levels, which helps to reduce noise. The invention also uses other techniques to reduce noise, and to reduce the noise transfer function in a power amplifier.

Abstract: The invention relates to a feedback circuit for a transimpedance amplifier, which is typically used for converting an input current from a photodiode into an output voltage. The feedback circuit of the present invention linearizes the transconductance feedback, as the input current signal varies, by providing a constant current source for supplementing the DC feedback current through a bypass transistor, thereby reducing a variation in the low frequency cut off.

Abstract: There is provided a high frequency power amplifier circuit capable of enhancing detection accuracy of an output level, necessary for feedback control of the high frequency power amplifier circuit, and capable of executing output power control with higher precision, With the high frequency power amplifier circuit, the detection of the output level, necessary for feedback control of the high frequency power amplifier circuit is executed by use of a current detection method, and in an electronic device comprising a differential amplifier for comparing an output power detection signal with an output level designation signal and for generating a signal for controlling a gain of the high frequency power amplifier circuit according to a potential difference between the two signals, a power source voltage with variation less than that for the power source voltage of the high frequency power amplifier circuit is used as the operational power source voltage of the output power detection circuit.

Abstract: An improved amplifier circuit which effectively combines two amplifier stages by utilizing two nested feedback loops so that an inverting amplifier topology is used with a FET input device, operating as a common source/emitter configuration cascoded by the inverting input of an opamp. The circuit operates as a non-inverting amplifier and is connnected to the drain or collector with local nested feedback to (a) independently control the loop gain, (b) linearize its own operation, and (c) control the stability of the circuit. Additional inputs can be summed using a non-inverting summing circuit. One application reduces distortion derived from a high impedance, capacitive input source.

Abstract: Circuits, methods, and systems are provided for opening a primary feedback loop in a transmitter. An auxiliary feedback loop can be closed when the primary feedback loop is opened, and a controller can match a gain of the primary feedback loop to another gain in the transmitter.

Abstract: A high frequency amplifier comprising a first trans-impedance amplifier, a second trans-impedance amplifier, a third amplifier, and a variant current source is provided. The first trans-impedance amplifier receives an input current and outputs a first output voltage accordingly. The second trans-impedance outputs a second voltage. The third amplifier receives the first and the second voltage. The variant current source is connected between the input terminal of the second trans-impedance and a ground terminal or a power supply source. The variant current source delivers a variant current to change the second voltage such that the second voltage may follow the first voltage. The input current flows into the first trans-impedance amplifier, while the variant current flows into the second trans-impedance amplifier. The input current flows out the first trans-impedance amplifier, while the variant current flows out the second trans-impedance amplifier.

Abstract: An amplitude regulation circuit which includes a maximum detection circuit which outputs a maximum signal MAX that is distorted to some extent during and around a time when a highest-level signal switches between signals V1, V2, and V3. The amplitude regulation circuit also includes a minimum detection circuit which outputs a minimum signal MIN that is distorted to some extent during and around a time when a lowest-level signal switches between signals V1, V2, and V3. Such distortions reduce variations in amplitude detection signal AMP that represents a difference between MAX and MIN. The amplitude regulation circuit amplifies rotor position signals H1 to H3 based on amplitude detection signal AMP according to AGC, thereby maintaining amplitudes of signals V1 to V3 constant while maintaining sinusoidal waveforms.

Abstract: A circuit is provided that includes a Cartesian feedback loop. The Cartesian feedback loop includes one or more operational amplifiers. At least one of the operational amplifiers includes two or more cascaded amplifier stages and one or more bypass amplifier stages. The bypass amplifier stages are connected in parallel with the cascaded amplifier stages.

Abstract: There is provided a high frequency power amplifier circuit capable of enhancing detection accuracy of an output level, necessary for feedback control of the high frequency power amplifier circuit, and capable of executing output power control with higher precision, With the high frequency power amplifier circuit, the detection of the output level, necessary for feedback control of the high frequency power amplifier circuit is executed by use of a current detection method, and in an electronic device comprising a differential amplifier for comparing an output power detection signal with an output level designation signal and for generating a signal for controlling a gain of the high frequency power amplifier circuit according to a potential difference between the two signals, a power source voltage with variation less than that for the power source voltage of the high frequency power amplifier circuit is used as the operational power source voltage of the output power detection circuit.

Abstract: A buffer circuit comprised of two matched stages is provided. The first stage develops a replica voltage that is used in the second stage as the input to a wide-band amplifier. The combination of the two feedback loops in the circuit result in improved linearity. The first amplifier dominates for moderate frequencies while the second amplifier takes over for high frequencies.

Abstract: A monolithic capacitance multiplication circuit serves to reduce the required die area when larger capacitance values are needed such as in filter and loop frequency compensation circuits. A current mirror/cascoding device arrangement reduces the effective series resistance of the multiplier capacitor. As a result, the multiplier topology exhibits improved bandwidth over prior art capacitance multiplier circuits.

Abstract: A limiting circuit includes an input transconductance stage, an output transconductance stage, a feedback transconductance stage, first and second resistive loads, and a level limiting circuit. The input transconductance stage is operably coupled to convert an input voltage signal into an input current signal. The first resistive load is operably coupled to convert the input current signal and a feedback current signal into an intermediate output voltage signal. The output transconductance stage is operably coupled to convert the intermediate output voltage signal into an output current signal. The second resistive load is operably coupled to convert the output current signal into an output voltage signal. The feedback transconductance stage is operably coupled to produce the feedback current signal based on the output voltage signal. The level limiting module is operably coupled to limit at least one voltage level of the feedback transconductance stage.

Abstract: A class-AB output stage circuit is configured with controllable reference voltages for providing stable quiescent current. An exemplary output stage circuit comprises one or more control circuits, such as feedback loops, configured to control and/or adjust the reference voltages within the class-AB circuit based on the output voltage and/or supply rail voltage levels. In addition, an exemplary output stage circuit can also comprise one or more clamp circuits configured to facilitate operation of the output stage circuit when the output supply is proximate to or exceeds a positive or a negative supply rail.

Abstract: A method and apparatus for reducing imbalances among the outputs of a plurality of driver devices connected in a parallel configuration to drive a common load. One driver is designated as the master, and suitable servo circuitry is provided to each of the other slave drivers, each servo being operative to force the output of its associated slave driver to accurately track the output of the designated master driver. The servo circuitry may be disposed to equalize either the output voltages or output currents of the several drivers to ensure load balancing among the drivers, to reduce cross-conduction currents and attendant power wastage and improve dynamic performance. The plurality of drivers may either operate in an open-loop configuration, or be enclosed within an overall negative feedback loop under the control of a separate controller that itself may be an amplifier.

Abstract: A method and apparatus is used to provide DC stabilization and noise reduction in a multistage power amplifier. The invention uses various feedback techniques to stabilize DC levels, which helps to reduce noise. The invention also uses other techniques to reduce noise, and to reduce the noise transfer function in a power amplifier.

Abstract: An operational amplifier arrangement having a non-linear amplifier and a linear amplifier, both having a pair of input terminals one of which is coupled to an arrangement input terminal, and both having an output terminal that is coupled to an arrangement output terminal. The output terminal of the non-linear amplifier is further coupled to the output terminal of the linear amplifier via a series impedance. The output terminal of the linear amplifier is coupled to the arrangement output terminal via a terminating impedance. The arrangement includes an active back termination arrangement coupled between the arrangement output terminal and either one of the pair of input terminals of the linear amplifier. Preferably, the linear amplifier is receiving a supply voltage that exceeds the supply voltage received by the non-linear amplifier.

Abstract: Disclosed is a low-noise active RC signal processing circuit, which comprises a feedforward section operable responsive to an input signal to provide an output at a predetermined gain, and a feedback section operable responsive to the output of the forward circuit to negatively feed back the output to the input signal of the feedforward section while giving a predetermined transfer characteristic to the output, so as to allow the processing circuit to have a transfer impedance characteristic equal to or less than the predetermined gain over the entire frequency range. The feedforward section is composed of a current-controlled voltage output circuit which includes a common-base transistor for receiving and inverting the input signal, and an emitter-follower transistor for outputting voltage, and has a transfer impedance defining the predetermined gain. The current-controlled voltage output circuit may also be constructed using an operational amplifier.

Abstract: There is provided a negative impedance converter, which has negative impedance conversion function by widening the available range of a generalized impedance converter. A generalized impedance converter is composed of two operational amplifiers Q1 and Q2 and four series-connected first to fifth impedance elements Z1 to Z4. The four impedance elements included in the generalized impedance converter are all set as the same resistor R1, and an impedance element Z6 is connected between the intermediate point B of the series-connected impedance elements and the ground. The magnitude of the impedance element Z6 is set smaller than that of load impedance element Z5. By doing so, the input impedance Z11? becomes negative, and the kind of the impedance is determined depending on the kind of the impedance elements Z5 and Z6.

Abstract: An amplitude regulation circuit which includes a maximum detection circuit which outputs a maximum signal MAX that is distorted to some extent during and around a time when a highest-level signal switches between signals V1, V2, and V3. The amplitude regulation circuit also includes a minimum detection circuit which outputs a minimum signal MIN that is distorted to some extent during and around a time when a lowest-level signal switches between signals V1, V2, and V3. Such distortions reduce variations in amplitude detection signal AMP that represents a difference between MAX and MIN. The amplitude regulation circuit amplifies rotor position signals H1 to H3 based on amplitude detection signal AMP according to AGC, thereby maintaining amplitudes of signals V1 to V3 constant while maintaining sinusoidal waveforms.

Abstract: A compensation circuit is provided for an amplifier including at least first and second amplifier stage. The circuit includes a first capacitance including one end that communicates with an input of the first amplifier stage. An amplifier includes a first gain, an input that communicates with an opposite end of the first capacitance, and an output. A second capacitance includes a first end that communicates with the output of the amplifier and an opposite end that communicates with an input of the second amplifier stage. A first impedence includes one end that communicates with the input of the first amplifier stage and an opposite end that communicates with an output of the second amplifier stage.

Abstract: A charge amplifier includes an amplifier, feedback circuit, and cancellation circuit. The feedback circuit includes a capacitor, inverter, and current mirror. The capacitor is coupled across the signal amplifier, the inverter is coupled to the output of the signal amplifier, and the current mirror is coupled to the input of the signal amplifier. The cancellation circuit is coupled to the output of the signal amplifier. A method of charge amplification includes providing a signal amplifier; coupling a first capacitor across the signal amplifier; coupling an inverter to the output of the signal amplifier; coupling a current mirror to the input of the signal amplifier; and coupling a cancellation circuit to the output of the signal amplifier. A front-end system for use with radiation sensors includes a charge amplifier and a current amplifier, shaping amplifier, baseline stabilizer, discriminator, peak detector, timing detector, and logic circuit coupled to the charge amplifier.

Abstract: An LNA for use as an input stage of a radio frequency tuner comprises an inverting amplifier stage and a transconductance stage. The amplifier stage has an input connected via an input resistance to an input of the amplifier and via a feedback resistance to an output of the amplifier stage. The transconductance stage passes a current through the input resistance which is substantially proportional to the output voltage of the amplifier stage.

Abstract: An audio apparatus is constructed for use in negative drive of a loudspeaker having an internal impedance to perform a desired amplitude-frequency characteristic. In the audio apparatus, an amplifier device drives the loudspeaker with a driving voltage. A feedback device performs a positive feedback of a signal corresponding to the driving voltage of the loudspeaker to the amplifier device with a variable feedback gain, thereby causing the amplifier device to generate a negative impedance effective to negate the internal impedance of the loudspeaker. An adjustment device decreases the variable feedback gain of the feedback device as a level of the driving voltage of the loudspeaker increases, thereby adjusting the amplitude-frequency characteristic of the amplifier device.

Abstract: A transconductance amplifier for inductive loads and a relevant inductive load driving method, the amplifier having an input stage receiving a driving signal (set-point), a power stage connected downstream of the input stage and connected to the load and an output stage fedback on the input stage to transfer a signal associated to the load. Advantageously, the input stage comprises at least a comparator receiving on one input the driving signal and on another input the output of the output stage. A delay block is also provided between the comparator output and the power stage to delay the comparator switching. This can be obtained also by using a hysteretic comparator.

Abstract: The operation of a bipolar transistor is controlled comprising by producing a first voltage that is a product of a static collector current of the bipolar transistor times an emitter resistance. The first voltage is then compared to a predetermined reference voltage to produce a control signal. Current is then injected a base of the bipolar transistor in response to the control signal. In a specific implementation, the first voltage, which is a product of the static collector current (Ic) of the bipolar transistor times its emitter resistance (RE) , is slaved to a predetermined reference voltage (Vref) whose value is substantially equal, to within a tolerance, to 13 mV at a temperature at or about 27° C.

Abstract: A wide dynamic range transimpedance amplifier for fiber optics receivers. An automatic transimpedance gain control and DC cancellation control feedback circuit include a pnp transistor that is connected with the input signal. The impedance seen at the emitter of the pnp transistor changes according to the average value of the photodiode input current. Thus, large signal amplitudes are attenuated at the input of the transimpedance amplifier by the transistor and small signal amplitudes are amplified. The transistor is a variable impedance that can increase the optical overload without diminishing or reducing the optical sensitivity of the transimpedance amplifier.

Abstract: A signal processing module provides high-gain amplification of received signals, while canceling some or all low-frequency error in the received signal. The signal processing module includes a multi-stage amplification series and a low-frequency error cancellation feedback loop.

Abstract: A continuous-time baseline restoration (BLR) circuit providing built-in pulse tail-cancellation, or BLR tail-cancel circuit, in constant fraction discriminator (CFD) arming and timing circuits. The BLR tail cancel circuit is applied at the output of constant fraction timing shaping filters and arming circuits to permit monolithic integrated circuit implementation of CFD circuits operating at high input signal count rates. The BLR tail-cancel circuit provides correction of dc offset and count-rate dependent baseline errors along with simultaneous tail-cancellation. Correction of dc offsets due to electronic device mismatches and count-rate dependent baseline errors is required for accurate time pickoff from the input signals. The reduction of pulse width, or pulse tail-cancellation is required to shorten the duration of high count rate signals to prevent the severe distortion caused by the occurrence a new signal superimposed on the tails of previous signals, a condition known as pulse pileup.

Abstract: The present invention includes an offset cancellation device having input return loss characteristics suitable for high frequency operation.

Abstract: A transimpedance amplifier (18) receives an audio signal from a power audio amplifier (14) and provides a variable power level to a loudspeaker (16). A first variable gain amplifier (28) receives the audio signal and provides a variable gain to a power amplifier (40). The output signal of the power amplifier drives the loudspeaker. A sense amplifier (52) subtracts a voltage representative of current flowing through the loudspeaker from a voltage applied to the loudspeaker and provides a difference signal. A second variable gain amplifier (70) receives the difference signal and provides a variable gain to a load amplifier (80). The gains of the first and second variable gain amplifiers are inversely proportional. A resistive element (84) having a real impedance is coupled between an output of the load amplifier and the input of the transimpedance amplifier to maintain the complex impedance of the loudspeaker at the output of the power audio amplifier.

Abstract: Disclosed is a transimpedance amplifier comprising a multistage amplifier and a feedback circuit coupled between a single ended input terminal and one of a plurality of differential output terminals of the multistage amplifier. The feedback circuit may control an input voltage at the single input terminal to substantially maintain a set or predetermined transconductance between the single ended input terminal and the differential output terminals.

Abstract: A measurement circuit for measuring input voltages in an automatic test system includes a pedestal source, a differential amplifier, and a feedback amplifier. The differential amplifier measures a “residue,” i.e., a difference between an input signal and a pedestal signal from the pedestal source, which is programmed to equal an expected input voltage. The feedback amplifier boosts the residue before it is presented to the differential amplifier, and thus allows the differential amplifier to be operated at lower gain than is typically used in conventional topologies. Consequently, the effect of the errors in the differential amplifier are reduced.

Abstract: An analog buffer with low harmonic distortion and low power supply voltage buffers a signal with wide voltage swing. The lower output voltage swing is increased, by adding a voltage level shifter to the feedback path of a servo. The upper output voltage swing is increased by coupling the output load to Vdd.

Abstract: Described are a circuit and system to provide an output signal in response to composite input signal comprising an AC signal component and a DC signal component. An amplifier provides an amplified voltage signal in response to a voltage representative of the composite signal. A filter may provide a filtered voltage signal having a magnitude that is representative of a magnitude of the DC signal component in response to the amplified voltage signal. A DC signal removal circuit may substantially remove at least a portion of the DC signal component from an input terminal in response filtered voltage signal.

Abstract: An inventive envelope-tracking amplifier is provided for improving gain and efficiency by dynamically shifting an operating point of active element (23) of power amplifying unit (10). A method for improving gain and efficiency is also developed for correcting an impedance of input, output or input/output of active element. An envelope DC current detected from RF signal is applied to variable impedance for radio frequency in an impedance matching circuit. Therefore, the variable impedance resulting from varying a signal level of a power amplifier corrects the variation of input or output impedance of active element by matching with the mated input, output or input/output. As a result, the gain and stability of amplifier is improved. A mobile communication terminal device is possibly adopting the same.

Abstract: A signal handling stage provides variable gain, for example for automatic gain control functions, in a radio frequency tuner. The stage comprises a transconductance stage having negative feedback via further transconductance stage. The output current of the transconductance stage is supplied to an AGC core, which steers the output current between output loads and loads for driving the transconductance stage in accordance with an AGC voltage. The amount of negative feedback is therefore varied in accordance with the AGC voltage. For relatively low gain, a large amount of feedback is used and this improves the distortion performance. For relatively high gain, the negative feedback is reduced but a good noise figure can be achieved.

Abstract: A signal processing module provides high-gain amplification of received signals, while canceling some or all low-frequency error in the received signal. The signal processing module includes a multi-stage amplification series and a low-frequency error cancellation feedback loop.

Abstract: An error amplifier stage (32) is supplied with an input signal from an input terminal (Vin) and a feedback signal produced by an output current/voltage converter stage (34) and amplifies the input signal with reference to the feedback signal to produce an amplified current signal which is delivered to a load driver stage (33). The error amplifier stage comprises an operational amplifier (6) of a voltage-controlled current-output type which is a transconductance amplifier having a transconductance gm. The transconductance amplifier includes a constant-current source and serves as a differential amplifying circuit based on the transconductance gm. A phase adjusting circuit for the transconductance amplifier is formed by a combination of a resistor (R10) and a capacitor (C10) connected in series between an output terminal of the transconductance amplifier and a ground potential.

Abstract: The present invention includes an offset cancellation device having input return loss characteristics suitable for high frequency operation.

Abstract: A re-circulating amplifier comprising a SAW filter with group delay characteristics for providing a time delay function.

Abstract: An apparatus consisting of a variable gain amplifier having an input and an output having a DC-offset compensation loop connected between the output and the input of the variable gain amplifier. The DC-offset compensation loop having a gain independent cutoff frequency.

Abstract: An amplifier that accurately amplifies signals over a wide bandwidth, including DC, has a voltage-to-current converter, a feed-forward resistive element, a buffer, an input resistive element, a feedback resistive element, and an operational amplifier. A first end of the feed-forward resistive element is coupled to an output of the voltage-to-current converter and to an input of the buffer. A first end of the input resistive element is coupled to an input to the voltage-to-current converter. A first end of the feedback resistive element is coupled to an output of the buffer. An inverting input of the operational amplifier is coupled to a second end of the input resistive element and to a second end of the feedback resistive element. A noninverting input of the operational amplifier is coupled to ground, and an output of the operational amplifier is coupled to a second end of the feed-forward resistive element.

Abstract: Various methods and apparatuses that multiply the effects of feedback current on an amplifier. In an embodiment, a buffer circuit controls the transition rate on an output pad of the buffer circuit. An amplifier has an input terminal and an output terminal. The output terminal couples to the output pad. A feedback component couples feedback current from the output pad to the input terminal. A current mirror multiplies the effects of the feedback current on the input terminal without increasing the feedback current through the feedback component.

Abstract: A differential transimpedance amplifier includes a differential transconductance stage to provide a current to a differential transimpedance stage. The differential transimpedance stage includes two gain stages and provides a voltage. A first feedback element is coupled in parallel with the differential transimpedance stage.

Abstract: A variable gain amplifier device comprises a variable gain amplifier circuit which amplifies a difference between an input signal and a feedback signal to output an output signal, a feedback circuit which supplies the feedback signal to the variable gain amplifier circuit, and a controller which controls the variable gain amplifier circuit and the feedback circuit to decrease a cutoff frequency of the feedback circuit according to increase of a gain of the variable gain amplifier circuit or vice versa.

Abstract: A transimpedance amplifier (18) receives an audio signal from a power audio amplifier (14) and provides a variable power level to a loudspeaker (16). A first variable gain amplifier (28) receives the audio signal and provides a variable gain to a power amplifier (40). The output signal of the power amplifier drives the loudspeaker. A sense amplifier (52) subtracts a voltage representative of current flowing through the loudspeaker from a voltage applied to the loudspeaker and provides a difference signal. A second variable gain amplifier (70) receives the difference signal and provides a variable gain to a load amplifier (80). The gains of the first and second variable gain amplifiers are inversely proportional. A resistive element (84) having a real impedance is coupled between an output of the load amplifier and the input of the transimpedance amplifier to maintain the complex impedance of the loudspeaker at the output of the power audio amplifier.

Abstract: A system for a closed power control feedback loop allows for the use of a non-linear amplifier for amplifying a phase modulated (PM) signal while introducing an inverse version of the desired amplitude modulated (AM) signal into the feedback loop using a variable gain element. By introducing an inverse version of the desired AM portion of the signal into the power control feedback loop, the non-linear, and highly efficient, power amplifier may be used to amplify only the PM portion of the signal, while the AM portion is introduced by the power control feedback loop. In another aspect of the invention, an inverse version of the AM portion of the desired transmit signal is introduced into the power control feedback loop of an amplifier that is amplifying both a phase modulated signal and an amplitude modulated signal.