Abstract: A method may include measuring a physical quantity associated with a load driven by an amplifier, generating a windowing function having a variable length and based on a number of samples of the physical quantity to be processed, applying the windowing function to the physical quantity, performing a transform on the physical quantity as filtered by the windowing function, and determining a characteristic of the load based on the transform.

Abstract: A current source has at least one gain component having a constant gain at frequencies below a frequency point, and having a gain inversely proportional to frequency at frequencies above the frequency point, the gain component having an input and an output, a source resistor connected in series with the output of the gain component, the gain component to regulate a voltage across the source resistor to be a source voltage, such that the gain of the gain component limits regulation by the gain component of the source voltage and an output voltage across a load between a high terminal and a low terminal, and a feedback component to receive at least a portion of the output voltage, the feedback component connected to the input of the gain component, the feedback component configured to reduce the gain of the gain component available to regulate the source voltage across the source resistor.

Abstract: Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker is provided for a power amplifier that amplifies an RF signal. The envelope tracker includes an error amplifier that controls a voltage level of a power amplifier supply voltage of the power amplifier based on amplifying a difference between a reference signal and an envelope signal indicating an envelope of the RF signal. The envelope tracker further includes a multi-level switching circuit that generates an error amplifier supply voltage based on sensing a current of the error amplifier, and uses the error amplifier supply voltage to power the error amplifier.

Abstract: In one example, a method to match a digital amplifier model to a real guitar amplifier comprises obtaining an amplifier output filter and an amplifier input filter for the real guitar amplifier, using the amplifier output filter and a model output filter to obtain a corrective output filter, using the amplifier input filter and a model input filter to obtain a corrective input filter, and applying the corrective input filter and the corrective output filter to the digital amplifier model. The amplifier output filter and the amplifier input filter can be obtained using exponential sine sweep (ESS) and a matched filter. Other examples and related methods and apparatuses are also disclosed herein.

Abstract: A converter circuit is provided that includes an amplifier circuit and further includes: a summing current resistor that exhibits nonlinear resistance coupled between a voltage node and a summing current node of the amplifier; a compensation resistor circuit includes resistors that exhibit nonlinear resistance; the compensation resistor circuit produces a compensation current at the summing current node that compensates for nonlinear current flow in the summing current resistor.

Abstract: A sensor amplifier arrangement includes an amplifier having a signal input to receive a sensor signal and a signal output to provide an amplified sensor signal, and a feedback path that couples the signal output to the signal input and provides a feedback current that is an attenuated signal of the amplified sensor signal and is inverted with respect to the sensor signal.

Abstract: A highly efficient, high control bandwidth and high-speed power supply with a linear driver and a switching regulator for regulating an output based on a control signal. The linear driver has a first input for receiving the control signal and a second input connected to the output for receiving negative feedback. The driver's output is controlled by its two inputs and has a capacitor connected in series with it to generate a capacitor voltage VC responsive to the DC and low frequency components in the driver's output. The switching regulator has a control input and a regulator output connected in a regulator feedback loop. The control input receives capacitor voltage VC and the regulator feedback loop minimizes capacitor voltage VC. Thus, switching regulator takes over the generation of DC and low frequency components, while the linear driver provides high frequency output current components.

Abstract: A transmitter for transmitting a transmission signal is disclosed. The transmitter includes: a gain stage, for receiving an input signal and amplifying the input signal according to a gain to generate an amplified signal; and an output stage, coupled to the gain stage, for receiving a first reference voltage signal and the amplified signal and utilizing the first reference voltage signal to perform a predetermined operation on the amplified signal to generate the output signal.

Abstract: A buffer amplifier has a power on state and a sleep state. During regular operation a coupling state of a load to an output node is detected using feedback voltage. In a sleep mode and in a power collapse mode a detection current is injected into the output node, to produce a voltage, and the coupling state of the load is detected from the voltage. Optionally, the detection current and detecting of the voltage on the output node is enables by a low duty cycle clock. Optionally, signals generated in detecting the coupling state are qualified through a debounce circuit.

Abstract: An apparatus and method for amplifying a transmission signals in multiple modes and multiple bands. The apparatus includes a tunable power amplifying module adapted to receive a plurality of signal types comprising multiple modes and multiple bands. The tunable power amplifying module includes a first and second power amplifier stages and a number of tunable matching networks configured to optimize an impedance value based on the mode and band of the signal to be amplified.

Abstract: This disclosure is directed to a frequency-selective low noise amplifier (LNA) with wide-band impedance and noise matching. The LNAS may include a closed loop circuit that supports wideband input matching. For example, the closed loop circuit may be configure to impedance match an input signal and provide a low noise figure. In addition, the LNA may include an open loop circuit that amplifies the input signal and provides a high output impedance. The open loop circuit may further include a selectivity filter that filters out frequencies outside a desired frequency band. The LNA may drive a tunable band-pass filter via the open loop circuit.

Abstract: A circuit arrangement and method for improving load regulation in an amplifier (e.g., LDO amplifier) uses a feedback circuit including a parallely connected feedback resistance Rf and a noise reduction feedback capacitance Cf, wherein an external capacitance has equivalent series resistance (ESR). The circuit arrangement includes a resistance Resr in the amplifier output, a junction point of the feedback resistance Rf and the feedback capacitor Cf being connected to a negative input of the LDO amplifier. Additionally, the circuit arrangement might include a resistance Rintentional in between Cf and Rf. The circuit arrangement provides good load regulation and better stability without increase in power/area. The arrangement supports external feedback mode providing design flexibility without compromising amplifier-stability, which provides high output current drive capability or enables driving heavy output capacitance.

Abstract: A system for controlling a power supplied to a load from a radio frequency amplifier system includes a radio frequency signal generator adapted for generating a radio frequency signal, an amplifier to which the radio frequency signal is supplied and that amplifies the radio frequency signal into a radio frequency power signal, a power coupler connected to the amplifying member for coupling the radio frequency power signals, where the power coupler includes a summing connection adapted for connection to the load and a compensating connection adapted for connection to a dissipative element. A first control value generating member is adapted for receiving a signal proportional to a power output from the power coupler at the summing connection and is adapted for generating a first control signal for controlling the amplifier or a current supply that supplies current to the amplifier.

Abstract: A voltage-controlled current source provides operation as either a differential current source for a floating load, or operation as a grounded current source when one end of the load is grounded. Switching between operation as a differential current source and operation as a grounded current source is automatic, and will accommodate significant lead resistance between the source and the load. Additionally, in absence of a grounded load the circuit can provide active common mode reduction using active feedback to reduce common mode voltage on the load.

Abstract: A wide bandwidth, multi-FET current sharing output stage, MOS audio power amplifier employs multiple feedback loops. An audio input is supplied to a voltage feedback amplifier stage driving a push-pull voltage gain/phase splitter stage. A bias adjustment stage driven from the push-pull voltage gain/phase splitter stage drives a current drive stage. The current drive stage drives an output stage comprising a plurality of paralleled current shared individual MOS output transistors driving an output node connected to a load. Up to three feedback loops are employed. A first voltage feedback loop comprises a voltage feedback stage having an input connected to a voltage divider driven from the first terminal of the load and an output connected to a feedback input node in the voltage feedback amplifier stage.

Abstract: A circuit for increasing damping factor in an audio amplifier adapted to be coupled to a load by output feed and return leads and components having an impedance causing a reduction in the damping factor, employs a balanced feedback network having first and second inputs and first and second outputs. The first input is coupled to a selected one of the feed and return lead near the output terminal and the second input is coupled to the same lead remote from the output terminal to thereby establish a series impedance between said first and second inputs representative of impedance of the selected output lead. The first output is coupled to the non-inverting input of the amplifier and the second output is coupled to the inverting input of the amplifier. The balanced feedback network positively feeds back a representation of the impedance to compensate therefor and thereby raise the damping factor of the amplifier. In an alternative embodiment, an isolating transformer is employed in the balanced feedback network.

Abstract: A transadmittance amplifier provides an output current that is proportional to an input voltage level. The output current drives a coil of an electric motor (the load) through a sense resistor, the voltage drop across the sense resistor providing an indication of the amount of current flowing through the coil. The indication provided by the sense resistor is applied across the differential input terminals of a feedback amplifier, which responds by outputting a feedback signal proportional to the output current. In one embodiment, the maximum output current is increased by providing a pair of complementary drive amplifiers.

Abstract: A speaker system includes a vertically oriented elongated tube supported on a ground surface, and open at upper and lower ends thereof; a woofer, mid-range speaker and tweeter mounted at a lower end of the tube, the woofer having a front driving face with an effective driving area, the woofer providing an in-phase audio signal directed upwardly through the tube and an out-of-phase ground wave audio signal directed in an opposite direction therefrom; an enclosure enclosing the woofer and mounting the tube on the ground surface; a restricted open area formed between a lower edge of the enclosure and the ground surface and being less than the effective driving area, the restricted open area being arranged to transmit the out-of-phase ground wave audio signal from the woofer in a direction transverse to the axial direction; and a driving circuit for driving the woofer and including a power amplifier for amplifying an input signal with a variable gain and supplying the amplified input signal to the woofer, a circu

Abstract: A load monitor module for measuring voltage and current supplied from an amplifier to a load is provided within an amplifier and includes a device for calculating an impedance of the load and an amount of power delivered to the load from the amplifier. The load monitor module includes a voltage measuring device and a current measuring device for accurately measuring the voltage and current of a generated test signal or an audio signal input the amplifier signal path without substantially altering the signal. The monitor module also includes a controller for controlling the performance of the amplifier and load according to the calculated load impedance and power input to the load from the amplifier.

Abstract: In a method and by an apparatus for correction of error signals and for forming of an arbitrary transfer function being independent of the quality of a payload (loudspeaker; H1) included in a signal amplification system, a control system (9) is used for supplying of the input signal to a basic amplifier (1) driving the payload. Said control unit includes a further amplifier (9) having an inverted input being supplied with a feedback signal from the output of the basic amplifier. In such a case the further amplifier involves only an inverted input, said input signal is supplied through one (4) of the resistors (3, 4) included in the feedback loop.

Abstract: An audio amplifier circuit which improves the efficiency, performance and power in a loudspeaker system. The circuit includes a discriminator differential amplifier which senses the motional voltage from the moving coil of a loudspeaker. The output signal from the differential amplifier is processed by the circuit into a correction voltage which is combined with the drive voltage and applied to the input of the loudspeaker.

Abstract: A voltage controlled current source with variable compliance produces a load current through a load impedance where the load current value is substantially independent of the value chosen for the load impedance. The value of the current is substantially proportional to the difference between a first and second input voltage, and is substantially inversely proportional to a value of resistance chosen as a sense resistance. The current source comprises two variable gain instrumentation amplifiers and a resistance means connected in series with the load impedance.

Abstract: A temperature compensation circuit used in a negative impedance driving apparatus such as an amplifier for driving a speaker as a load. A current flowing through the load is detected by a detection element connected to the load, and fed back therefrom, so that negative impedance driving is effected on the load. The detection element is set its temperature coefficient to be equal to or slightly larger than a temperature coefficient of the load, thereby the positive feedback gain is changed upon changing the temperature of the load so that negative impedance driving state is compensated. In another aspect of the invention, a temperature sensitive element or temperature detecting element for sensing or detecting the temperature of the detection element is arranged to change the positive feedback gain and compensate the negative impedance driving state.

Abstract: Negative-feedback amplifier provided with an active amplifier section operating approximately as a nullor and a negative feedback section, the amplifier having a high loop gain. The active amplifier section is constructed in balanced form with two nullors connected in balance, and the negative-feedback section is composed of passive impedances and comprises two negative-feedback loops. In one embodiment each nullor has a series-coupling circuit and a parallel-coupling circuit at the input port. As a result an accurately defined or characteristic input impedance is obtained, and a series- or parallel-coupling circuit is formed in both negative-feedback loops at the output port, so that a high (current output) or low (voltage output) output impedance, respectively is obtained. In another embodiment each nullor has a series-coupling circuit and a parallel-coupling circuit at the output port.

Abstract: A method of improving the frequency reproduction at frequencies higher than a certain break frequency (fs) of a bass amplifier known per se within the audio frequency range. The amplifier has a low-pass filter portion (ACE1) and a power amplifier portion (EF) with a current feedback portion (ACE2) in order to get a negative output impedance against the loudspeaker. According to the invention high-pass filtration is carried out from the break frequency (fs) and upwards to about 20 kHz of the signal coming to the amplifier and thereafter a phase shift (.rho.) is carried out so that a cophasal state is obtained at the break frequency (fs) before the power amplifier portion (EF).

Abstract: A current source type current output circuit for applying to a load a current which is proportional to an input includes an amplifier of the type receiving a current and producing a voltage, and a feedback circuit for feeding back an output of the amplifier to an input terminal of the amplifier. The feedback circuit is made up of a first, a second, and a third current mirror circuit, and a first, a second, and a third resistor. An output terminal of the amplifier is connected to an input terminal of the second current mirror circuit via the third resistor and to an input terminal of the first current mirror circuit via a series connection of the first and second resistors. The load is connected to the intermediate point of the serial connection of the first and second resistors. An output terminal of the second current mirror circuit is connected to an input terminal of the third current mirror circuit.

Abstract: A system which corrects for adverse characteristics such as reactance, inertia and resonances of a power amplifier driven load such as a speaker or multiple speaker system. Program voltage is applied to a reference load which has electrical characteristics which simulate characteristics of the driven load, and the response of the reference load to the program is used to develop a correction voltage signal for the driven load. The program and the correction voltage signal are simultaneously applied to the power amplifier to simultaneously reproduce the program and correct for the adverse characteristics of the load.

Abstract: An efficient power amplifier for high-capacitive device C2 in load string 10. The load string 10 includes a reference capacitor C3, a resistor R1, and an inductor L1. A large capacitor C1 is connected to load string 10 through high voltage power bridge 28. A current sensing feedback 30 is utilized to produce a triangular waveform of current in load string 10 for causing charge to be alternatively removed from capacitor C1 and delivered to device C2 through inductor L1 and then returned to capacitor C1 with any losses replenished by the dc power source. A voltage sensing feedback 14 is used to modulate the triangular current waveform. The power amplifier behaves as a stable linear dc coupled operational amplifier delivering a large reactive current with only slight losses.

Abstract: A driver circuit for applying a first signal having a desired wave form, frequency and peak to peak voltage to a coaxial transmission line which also has applied to it a second signal having a substantially higher frequency. An operational amplifier has the first signal applied to its noninverting input terminal. The output of the operational amplifier is applied across the primary winding of a driver coupling transformer through an inductor which provides high impedance to the second signal. The voltages induced in the secondary winding of the driver transformer are applied to the transmission line. The primary winding of a feedback transformer is connected in parallel with the secondary winding of the driver transformer. The voltage induced in the secondary winding in the feedback transformer are applied by a feedback circuit including an R.C. filter to the inverting input terminal of the operational amplifier. The signal applied to the inverting input terminal includes both an A.C. component and a D.C.

Abstract: A system which corrects for adverse characteristics such as reactance, inertia and resonances of a power amplifier driven load such as a speaker or multiple speaker system. Program voltage is applied to a reference load which has electrical characteristics that simulate characteristics of the driven load, and the response of the reference load to the program is used to develop a correction voltage signal for the driven load. The program and the correction voltage signal are simultaneously applied to the power amplifier to simultaneously reproduce the program and correct for the adverse characteristics of the load.

Abstract: An electric amplifier adapted to respond to an input signal of either polarity comprising a first differential amplifier OP1 which is arranged to drive through a load L a current whose value varies with the input but is independent of the load value and a second differential amplifier OP2 arranged to maintain the ratio of the amplifier output potentials relative to a datum potential at a predetermined value so that by appropriate choice of the datum potential and the predetermined ratio value the available output potential swing with a given supply voltage can be maximized.

Abstract: An amplifier comprising a first and a second amplifier element, whose outputs are connected to a load, a difference circuit which comprises a comparator, in which the output signal of the first amplifier element is compated with the input signal thereof to produce a correction signal which is applied to second amplifier element, and a second substantially identical difference circuit which comprises a comparator in which the output signal of the second amplifier element is compared with the input signal thereof to produce a correction signal which is applied to the first amplifier element; a desired signal to be amplified being applied to both amplifier elements. The two amplifier elements, which may be preceded by preamplifiers, take the form of power amplifiers. Because the distortion signals appear at the load as "common mode" signals, the overall distortion becomes substantially zero in the case of equal attentuation in the two difference circuits.

Abstract: A voltage-to-current converter circuit comprises first and second amplifiers each having a noninverting input, an inverting input and an output, the noninverting inputs of the first and second amplifiers being respectively connected to an input terminal for receiving an input signal and circuit ground, a first impedance element connected between the inverting input of the first amplifier and circuit ground, a second impedance element connected between the output and the inverting input of the first amplifier, a third impedance element connected between the output of the i first amplifier and an output terminal to be connected to a load, a fourth impedance element connected between the inverting input of the second amplifier and the output terminal, a fifth impedance element connected between the output and the inverting input of the second amplifier, and a sixth impedance element connected between the output of second amplifier and the inverting input of first amplifier.

Abstract: A vibration densitometer having a magnetostrictive drive with a coil, and a crystal pick-up. A loop circuit including a driver amplifier provides the coil with current which leads the crystal voltage by 90 degrees for maximum efficiency. The driver amplifier is unusually small, inexpensive and accurate.

Abstract: According to the present invention circuit means and method are provided which correct for variations in an amplifier load such as a speaker by sensing the load current, developing a feedback signal related to the load current, comparing this feedback signal with the amplifier program, and instantaneously adjusting the gain of the amplifier to compensate for load current deviations from the program applied to the amplifier. By this means the performance of the speaker or other load that is driven by the amplifier is positively controlled and forced to track accurately with the program applied to the amplifier despite such opposing factors as reactance or inertia of the load, whereby the acoustic or other load response is a substantially accurate reproduction of the program.

Abstract: An arrangement to provide feedback to amplifier systems incorporating an electrical load. A current transformer in conjunction with a resistor is incorporated to provide a feedback correction signal to an amplifier which corrects for distortion caused by both the amplifier and the inductive load. A first embodiment provides a single-ended amplifier driving a load and incorporates the current transformer between the output of the amplifier and the load. The secondary winding of the transformer is in series with the input to the amplifier, and a resistor is connected across the secondary winding. The transformer determines the frequency bandwidth of the entire amplifier system, and the resistor value determines the gain of the amplifier. Such a configuration provides negative feedback to the amplifier which is directly proportional to changes in current in the load due to distortions caused by the amplifier or load.

Abstract: In a high-fidelity sound reproducing system wherein the speaker is located remotely from the amplifier and therefore the electrical signals reaching the speaker are subject to distortion from the capacitive and inductive reactance of the conductors joining the amplifier to the speaker, and further subject to pickup of hum and other forms of interference, the distortion of the signal is substantially eliminated by the use of a negative feedback network connected between the input terminal of the load and the input terminal of the amplifier and by a positive feedback network connected between the input terminal of the amplifier and the return terminal of the load, the feedback loops operating on the amplifier to alter its output in such a way that the signal applied at the terminals of the remote speaker more nearly resembles the signal applied as an output to the amplifier.

Abstract: A power amplifier device comprising first and second output terminals connected to a loudspeaker, and a power amplifier having a non-inverting input supplied with an audio signal, an output connected to the first output terminal and an inverting input. The second output terminal is grounded through a first resistor and connected to an input of an inverting amplifier having a gain of -1. An output of the inverting amplifier is connected to the inverting input of the power amplifier through a second resistor. The output of the power amplifier is connected to its inverting input through a third resistor. The ratio of the third resistor to the second resistor is selected to be larger than 1 whereby the output impedance of the power amplifier device as seen from the first and second output terminals is made to be negative.

Abstract: Signal currents corresponding to a voltage to be converted into current or to a current to be amplified are applied to one input of an operational amplifier and its other input is referenced to ground. Its output is connected via a power amplifier and a small resistance to an output terminal and means are provided for supplying current proportional to the voltage across the resistance to the signal input of the operational amplifier with such polarity as to tend to cancel the signal current present thereat.

Abstract: An interface circuit for a transmission line between a remote transmitter and a central control room instrument includes an operational amplifier. The input of the operational amplifier is derived from the current drawn by the remote transmitter. The output signal of the operational amplifier is applied to control the operation of a transistor current controlling amplifier. The current controlled by the transistor amplifier is drawn from the same source as the current drawn by the transmitter. Because of a feedback connection from the transistor amplifier to the input of the operational amplifier, the output current from the transistor amplifier is a mirror image of current drawn by the transmitter. With that arrangement, both the power supply and the remote transmitter may be grounded without loss of accuracy or reliability.

Abstract: Current and voltage feedback are used in separate frequency dependent major loops around a high gain broadband amplifier to produce frequency shaped gain and matched input and output impedances.

Abstract: A distortion-free amplifier for electric signals has a high-quality low-power amplifier-section. In addition there is a high-power amplifier-section which delivers the majority of the current to the load. A feedback signal is derived which is a measure of the output current of the high-power section and not the low-power section. The feedback signal is applied to the inputs of both amplifier-sections negatively in an amount such as to remove from the combined output currents in the load any distortion occurring in the contribution from the high-power section.