Abstract: A method for digitally processing audio signals to emulate the effects of vacuum tube amplifiers and preamplifiers, musical instrument amplification systems, and distortion effects. By use of a parametrically-controlled non-linear transfer function, non-linear filters, feedback elements, and power-law function models, the dynamic behavior and distortion effects of tube amplification stages are simulated. This provides users with the capability to reproduce the desired sounds of vintage and modern tube amplifier systems and effects with the conveniences and control associated with digital signal processing systems and software.

Abstract: A level-shifting amplifier is provided for level-shifting an input signal with a voltage magnitude that exceeds a supply voltage of the amplifier. In operation, the amplifier has an input impedance of greater than 100M Ohms.

Abstract: A Gigabit/s transimpedance amplifier system includes a forward-path amplifier section with a very large bandwidth and an overall frequency-selective feedback section which is active only from DC to low frequencies. The forward-path of the amplifier comprises a regulated cascode for receiving the input signal, a regulated cascode for receiving the feedback signal, a single-ended to differential converter and an output buffer. Stability and frequency selection is achieved by a bandwidth-limited operational amplifier in the feedback path. The Miller multiplication of a capacitive means in the operational amplifier creates a low-frequency pole and stabilizes the feedback loop and thereby limits the frequency range of the feedback.

Abstract: A low noise amplifier (LNA) is discussed. In implementations, a LNA may include a feedback section coupled to a transistor. The feedback section may have a resistive portion including a buffer and a resistor. A capacitor may be connected in parallel with the resistor. In additional implementations, an integrated circuit may include a second transistor connected to the drain of the first transistor. A feedback section may be coupled across the first and second transistors. The feedback section may include a buffer, a resistor and a capacitor connected in series, so that the terminal of the buffer is connected to the drain of the second transistor while the terminal of the resistor is connected to a source on the first transistor.

Abstract: The apparatus and method provide a readout technique and circuit for increasing or maintaining dynamic range of an image sensor. The readout technique and circuit process each pixel individually based on the magnitude of the readout signal. The circuit includes a gain amplifier amplifying the readout analog signal, a level detection circuit for determining the signal's magnitude, a second gain amplifier applying a gain based on the signal magnitude and an analog-to-digital converter digitizing the signal and a circuit for multiplying or dividing the signal. The method and circuit allow for a lower signal-to-noise ratio while increasing the dynamic range of the imager.

Abstract: An apparatus comprises a first substrate and a second substrate. The first substrate includes an optoelectronic device and a matching circuit. The second substrate includes a driver circuit. A frequency response of the optoelectronic device is changed by the matching circuits. The first substrate is coupled to the second substrate via respective bond pads from the first and second substrates such that the matching circuit is interposed between the optoelectronic device and the driver circuit.

Abstract: An amplifier circuit for converting the current signal from an optical receiving element into a voltage signal. The amplifier circuit includes a transimpedance amplifier having a differential amplifier and a feedback resistor, a first adjustable resistor which is connected in parallel with the feedback resistor and whose resistance value is defined by a first control signal, and a series circuit connected in parallel with the feedback resistor. The series circuit includes a first capacitor and a second adjustable resistor, whose resistance value is defined by a second control signal. The two adjustable resistors are preferably formed as MOS resistors and have the same control signal applied to them. The amplifier circuit permits the provision of a high dynamic range during the operation of a transimpedance amplifier.

Abstract: A power amplification circuit, and a communication device using the same, which are capable of suppressing gain decreases of a power amplifier due to increases in input signal power in a state near the saturation operation, capable of reducing its size, and low in distortion and high in efficiency. The power amplification circuit includes a power amplifier and a negative feedback circuit connected between a signal input terminal and a signal output terminal of the power amplifier. Impedance of the negative feedback circuit depends on a signal voltage occurring across the negative feedback circuit. By adjusting the characteristic that the negative feedback quantity of the negative feedback circuit to the power amplifier is variable depending on input signal power, gain fluctuations of the power amplifier due to increases or decreases of input signal power or output signal power around a specified output signal power are suppressed.

Abstract: An R.F. power amplifier circuit comprising a power control loop is described. The power control loop includes an R.F. power amplifier having a power control input and a power supply input as well as at least one feedback path coupled between the power control input and the power supply input of the power amplifier. The feedback path includes at least one variable loop element that has a control terminal configured to reduce variations of control loop parameters.

Abstract: An output-compensated buffer includes a buffer circuit that receives an input signal and produces an output signal responsive thereto at an output terminal, the buffer circuit including an input source-follower circuit that receives the input signal. A feedback circuit is connected to the output terminal and to the input source follower circuit and operative to vary an input capacitance of the source follower circuit responsive to the output signal at the output terminal. The input source follower circuit preferably includes a bias terminal coupled to a power source, and the feedback circuit is preferably capacitively coupled to the bias terminal. According to another aspect, an image capture device includes a charged coupled device (CCD) that generates a video signal.

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: A signal processing circuit comprises a difference stage for receiving an input signal to be processed and a feedback signal taken from an output signal of the circuit. The difference stage generates a difference signal corresponding to the difference between the input and feedback signal. An integrator stage is coupled to the difference stage to receive the difference signal and output an integrated signal. A time continuous pulse width modulating stage is coupled to the integrator stage to receive the integrated signal and to modulate the signal with reference to a continuously varying carrier signal. A continuous time feedback path is coupled to the output of the modulating stage and an input or the difference stage. The integrator stage comprises at least two integrators to provide second or higher order integration.

Abstract: An optical component, such as an optical receiver, is provided that includes a detector configured to receive a signal from an optical fiber and to communicate with a translationl module of the optical component. A transimpedance amplifier of the optical component is configured to receive an electrical signal from the detector and to transmit an amplified signal to the translation module. The transimpedance amplifier is configured for a controlled low cutoff frequency as optical power to the transimpedance amplifier increases, so that the optical sensitivity of the transimpedance amplifier is not traded for optical overload.

Abstract: A photoelectric current and voltage converting circuit converts a photo current Ipd generated by the input to photo diode into a voltage Va by a feedback resistor connected to an inverting input and an output of an amplifier, and compares the output voltage Va with a threshold voltage Vth from a reference voltage circuit to output a binary signal. Divided voltage Vb gained from a connecting node of the feedback resistors is inputted to a non-inverting input of the reference voltage circuit and is offset to a higher voltage by Vos to generate a threshold voltage Vth. As a result, the threshold voltage Vth can be supplied which impedance is low and robust to noise, and errors of the comparator or jitter of the output of the comparator are suppressed.

Abstract: A photoelectric current and voltage converting circuit includes a light receiving element, an amplifier, a feedback resistor, an offset resistor, a constant current source, and a comparator. A feedback resistor is connected between the input and the output of the amplifier and converts photo current into voltage. An terminal of the offset resistor is connected to the output of the amplifier. The constant current source is connected to another terminal of the offset resistor. The comparator compares the connected point of the offset resistor and the constant current source with a reference voltage and outputs a binary signal. The reference voltage is an input voltage of the amplifier or the divided voltage of the intermediate point of the feedback resistor.

Abstract: A negative feedback amplifier which alleviates reduction in band width and effectively protects an amplifier from electrostatic discharge (ESD). A node is provided at the midpoint of a feedback resistor connected between an output terminal and an input terminal of an amplifier. Each of ESD protective diodes are connected between the node and respective power terminals. ESD threshold voltage and band width vary in accordance with the resistance of a resistor between the input terminal and the node. Setting the resistance of the resistor at 10 to 100? makes it possible to secure the necessary ESD threshold voltage while hardly reducing band width.

Abstract: The invention provides an amplifier circuit made by digital CMOS processes, the amplifier circuit comprising a main operational amplifier with at least one input and at least one output and a feedback loop including a non-linear gateoxide capacitor, wherein a voltage control means is connected to the main operational amplifier to provide a voltage difference between the output common mode voltage and the input common mode voltage of the main operational amplifier to apply a DC biasing voltage across the non-linear gateoxide capacitor sufficient to operate the non-linear gateoxide capacitor in a bias range where the capacity of the none-linear gateoxide capacitor is almost independent of the applied voltage comprising the bias voltage plus a signal voltage.

Abstract: A power amplification circuit, and a communication device using the same, which are capable of suppressing gain decreases of a power amplifier due to increases in input signal power in a state near the saturation operation, capable of reducing its size, and low in distortion and high in efficiency. The power amplification circuit includes a power amplifier and a negative feedback circuit connected between a signal input terminal and a signal output terminal of the power amplifier. Impedance of the negative feedback circuit depends on a signal voltage occurring across the negative feedback circuit. By adjusting the characteristic that the negative feedback quantity of the negative feedback circuit to the power amplifier is variable depending on input signal power, gain fluctuations of the power amplifier due to increases or decreases of input signal power or output signal power around a specified output signal power are suppressed.

Abstract: An optical component is provided that includes a detector configured to transmit an input current to a transimpedance amplifier that includes an automatic transimpedance gain control and DC cancellation control feedback circuit having variable impedance circuitry. Open loop gain of the feedback circuit is independent of the average input current as the input current increases. The feedback circuit includes first and second pnp transistors arranged so that their respective bases are connected and so that an emitter terminal of the first pnp transistor is connected to the input of the transimpedance amplifier, and the impedance seen at the emitter terminal changes according to the average value of the input current. The emitter size of the second pnp transistor is a factor N smaller than emitter size of the first pnp transistor. N can be selected to adjust the gain control and low corner frequency variation with input power.

Abstract: A light-receiving circuit of an optical coupling device may include a dummy photodiode arranged in a vicinity of a photodiode. The dummy photodiode and photodiode may convert received optical signals to photoelectric current. Amplified photoelectric current outputs from current-to-voltage converting amplifiers may be compared and subjected to waveform shaping by a hysterisis comparator for improving a common mode rejection ratio. Negative feedback paths and/or circuits of the converting amplifiers may include impedance variable circuits. The impedance variable circuits may reduce impedance based on the level of the input photoelectric current.

Abstract: The amplifier device contains a first amplifier element having a first input and a first output. The first output is fed back via a negative feedback path to the input. The negative feedback path contains a controlled current source which brings about a reduction in the noise and also a real finite input impedance.

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: In signal sources having a high impedance, typically a capacitive “signal source” such as capacitor-microphone capsules, it is common practice to use amplifier circuits that include means for coupling signals and determining operating points in addition to the actual amplifier having a high-resistance, non-inverting input. For setting the operating points of the signal source and the amplifier, separate bias-voltage sources are provided; these are coupled to the signal source and the non-inverting input, respectively, of the amplifier via a coupling impedance. At least one coupling capacitance is disposed in the signal path between the signal source and the non-inverting input of the amplifier. To attain a considerable noise gain without the disadvantage of very high idle times in this type of amplifier circuit, it is proposed that the coupling impedances be formed from a nonlinear resistance (D1, D2 or D3, D4) and an ohmic resistance (R3 or R4) connected thereto in series.

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: A power amplification circuit, and a communication device using the same, which are capable of suppressing gain decreases of a power amplifier due to increases in input signal power in a state near the saturation operation, capable of reducing its size, and low in distortion and high in efficiency. The power amplification circuit includes a power amplifier and a negative feedback circuit connected between a signal input terminal and a signal output terminal of the power amplifier. Impedance of the negative feedback circuit depends on a signal voltage occurring across the negative feedback circuit. By adjusting the characteristic that the negative feedback quantity of the negative feedback circuit to the power amplifier is variable depending on input signal power, gain fluctuations of the power amplifier due to increases or decreases of input signal power or output signal power around a specified output signal power are suppressed.

Abstract: A wide dynamic range transimpedance amplifier with a low cut off frequency at high optical power. An automatic transimpedance gain control and DC cancellation control feedback circuit includes variable impedance circuitry. An emitter terminal of a first pnp transistor is connected to the input of the transimpedance amplifier. The impedance seen at the emitter terminal changes according to the average value of the input current. Open loop gain of the feedback loop including the first pnp transistor is not dependent on the average input current as the input current increases. A base terminal of the first pnp transistor is connected to a base terminal of second pnp transistor. Emitter size of the second pnp transistor is some factor N smaller than emitter size of the first pnp transistor. N can be configured to adjust the gain control and low corner frequency variation with input power.

Abstract: A wide dynamic range transimpedance amplifier with a low cut off frequency at high optical power. An automatic transimpedance gain control and DC cancellation control feedback circuit includes variable impedance circuitry including 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. The transconductance of the pnp transistor is not dependent on the average input current as the input current increases. The low cutoff frequency thus approaches an upper limit as the input current increases and does not increase exponentially.

Abstract: A negative feedback amplifier which alleviates reduction in a band, and effectively protects an amplifier from electrostatic discharge (ESD). A node is provided at the midpoint of a feedback resistor connected between an output terminal and an input terminal of an amplifier. Each of ESD protective diodes is connected between the node and each power terminal. ESD threshold voltage and the band vary in accordance with the resistance of a resistor between the input terminal and the node. Setting the resistance of the resistor at 10 to 100&OHgr; makes it possible to secure the necessary ESD threshold voltage with hardly reducing the band.

Abstract: A transimpedance amplifier system includes a first gain stage to receive an input signal. A second gain stage is coupled to the first gain stage to provide a first output. A first passive feedback element is coupled in parallel with the second gain stage. A general feedback element is coupled in parallel with the first gain stage and the second gain stage. A replica biasing stage is included to provide a second output. A replica feedback element is coupled in parallel with the replica biasing stage.

Abstract: A signal processing circuit using positive feedback while keeping the open loop gain of the circuit less than 1 to avoid oscillation. The circuit includes a floating signal source, a low gain amplifier, a feedback element, and a second stage circuit. The floating signal source produces a voltage that is impressed across the feedback element by the feedback system. The feedback element processes the voltage into an output current. The output current is passed through an output current node to the second stage circuit where the output current can be used as a current reference or be further processed. The output from the low gain amplifier may be used as a voltage output node that provides a voltage that is an amplification of the voltage produced by the floating signal source. The signal processing circuit may be embedded in another circuit, including additional stages of the signal processing circuit.

Abstract: A transimpedance amplifier for a high-speed optical fiber communication receiver includes an operational amplifier having a current input and developing a voltage output. A variable peaking capacitor is connected across the operational amplifier. A control circuit is operatively coupled to the variable capacitor for controlling capacitance to widen bandwidth of the transimpedance amplifier.

Abstract: A system and method of processing received signals in an ultrasound imaging system is disclosed. In the system, the received signals are amplified by means of a gain controlled amplifier, and the gain of the amplifier is varied, by varying the load capacitance, as a function of depth (time) to compensate for the attenuation of ultrasonic energy at different depths within a patient's body.

Abstract: An imaging element that includes a photodiode and an amplifier for integrating photocurrent from the photodiode. The amplifier includes an input follower, a level shifter, and an output amplifier. The level shifter provides DC isolation between the follower output and the output amplifier. The input follower includes an input transistor connected to the photodiode, and the output amplifier has an input transistor connected to the level shifter. The sizes of these transistors are chosen such that the area of the input transistor in the input follower is less that the area of the input transistor in the output amplifier. The input follower preferably utilizes PMOS transistors.

Abstract: A preamplifier for use in an optical signal receiver is provided, which is capable of circumventing a problem of oscillation or shortage of bandwidth even in case an employed photodiode has a capacity value which inherently causes oscillation or shortage of bandwidth. The preamplifier includes a variable gain amplifier connected to a light receiving element for converting a received light signal to electric current; a variable feedback resistor connected to an input and output of the variable gain amplifier; and a band detection circuit for detecting a signal band amplified by the variable gain amplifier, wherein a band control signal obtained from the band detection circuit controls the band of the variable gain amplifier.

Abstract: A transimpedance amplifier system includes a first gain stage to receive an input signal. A second gain stage is coupled to the first gain stage to provide a first output. A first passive feedback element is coupled in parallel with the second gain stage. A general feedback element is coupled in parallel with the first gain stage and the second gain stage. A replica biasing stage is included to provide a second output. A replica feedback element is coupled in parallel with the replica biasing stage.

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

Abstract: An apparatus comprising a common-base amplifier circuit and a control circuit. The amplifier circuit may be configured to generate an output signal having a transimpedance bandwidth in response to an input signal. The control circuit may be (i) coupled between the output signal and the input signal and (ii) configured to implement input signal control to provide input overload current capability.

Abstract: In a preferred embodiment, a charge sensitive preamplifier for a radiation detector, including: an amplifier having a JFET input (stage) and a capacitive feedback element, the amplifier producing an output voltage (pulse) proportional to a charge (pulse) deposited at the JFET input by the radiation detector; and circuitry connected to the amplifier output and to a source node of the JFET to provide to the source node a pulsed reset signal.

Abstract: A signal processing circuit using positive feedback while keeping the open loop gain of the circuit less than 1 to avoid oscillation. The circuit includes a floating signal source, a low gain amplifier, a feedback element, and a second stage circuit. The floating signal source produces a voltage that is impressed across the feedback element by the feedback system. The feedback element processes the voltage into an output current. The output current is passed through an output current node to the second stage circuit where the output current can be used as a current reference or be further processed. The output from the low gain amplifier may be used as a voltage output node that provides a voltage that is an amplification of the voltage produced by the floating signal source. The signal processing circuit may be embedded in another circuit, including additional stages of the signal processing circuit.

Abstract: A method and system to compensate for DC and low frequency current produced by a photodiode that is illuminated with an optical data stream is described. An optical data stream ideally produces no current from a photodiode when the bit is a 0 and produces a current proportional to the optical power when the bit is a 1. Thus, the current produced from the photodiode consists of a DC component, which is typically half the current of a 1 bit (if there is an equal number of 1s and 0s in the data), and a high frequency component that carries the data. The DC component can interfere with the signal path's ability to process the information carrying component of the photodiode current, by causing a fixed offset to propagate and be amplified through it. This offset distorts the voltage signal at the output of the signal path, and must therefore be cancelled early in the path; usually in the first transimpedance stage or just after it.

Abstract: Transimpedance amplifiers that provide moderate bandwidth and very large overdrive current capabilities while consuming a minimum amount of power supply current. Existing transimpedance amplifier topologies use a quiescent current somewhat larger than the overdrive current that must be tolerated while the present invention reduces the value of the quiescent current and can tolerate bi-directional overdrive current several times larger than the current consumption of the circuit itself. The preferred embodiment of the invention is arranged such that stability of the circuit is ensured under all operating conditions, including overdrive conditions. Various embodiments are disclosed.

Abstract: A signal processing circuit using positive feedback while keeping the open loop gain of the circuit less than 1 to avoid oscillation. The circuit includes a floating signal source, a low gain amplifier, a feedback element, and a second stage circuit. The floating signal source produces a voltage that is impressed across the feedback element by the feedback system. The feedback element processes the voltage into an output current. The output current is passed through an output current node to the second stage circuit where the output current can be used as a current reference or be further processed. The output from the low gain amplifier may be used as a voltage output node that provides a voltage that is an amplification of the voltage produced by the floating signal source. The signal processing circuit may be embedded in another circuit, including additional stages of the signal processing circuit.

Abstract: An electrical circuit is provided for controlling nonlinear paths. A first linearization block and a second linearization block are provided, which may each have a characteristic curve that is the inverse of that of the control path. The first linearization block is configured in a feedback path running from the output of the control path to an input of a regulator. The second linearization block is configured for supplying a reference variable to an input of the regulator. Nonlinearities in the control path are thus linearized. In consequence, major changes in the reference variable are acceptable. The linearization blocks can be designed in a simple manner and require only a small surface area, since low power levels are normally produced at the inputs of an operational amplifier contained in the regulator. An additional advantage resulting from this is compensation for temperature drift of the two linearization blocks.

Abstract: An image display device has an image display section including an insulating substrate having a matrix of pixels formed on an inner surface thereof and a liquid crystal layer sandwiched between the insulating substrate and a substrate opposing the insulating substrate. The image display device includes signal lines, driver circuits for driving the matrix of pixels via the signal lines, voltage amplifiers formed by polycrystalline semiconductor TFTs and each coupled between one of the signal lines and a corresponding one of the driver circuits. The signal lines, the driver circuits and the voltage amplifiers are formed on a surface of the insulating substrate on a side thereof facing the liquid crystal layer. A channel, a source and a drain of the polycrystalline semiconductor TFTs each are formed of a polycrystalline semiconductor film. A gate insulating film and a gate electrode are superposed on the polycrystalline semiconductor film in the order named.

Abstract: A set of clamping diodes between terminals of a transistor acting as a power amplifier is configured to allow overvoltage at the output terminal of the transistor to travel through those clamping diodes to provide feedback used by the transistor for gain control.

Abstract: A device for converting low currents, applied by a non-ideal current source to an input of the device, into voltage signals comprises a converter for converting the low currents into voltage signals, at least one feedback branch, and a coupler. The output of the converter is fed back to an input of the converter by the feedback branches and the coupler. The coupler is wired so that control currents supplied by the feedback branches are applied to the input of the converter via the coupler to control the low currents applied by the non-ideal current source at the input of the device. The control currents are applied to the input of the converter via the coupler with a reduction of capacitive, inductive, and ohmic influence of the feedback branches and with an amplitude matching of the control currents.

Abstract: A fully balanced transimpedance amplifier for high speed and low voltage applications is provided. An input stage of the amplifier uses a matched pair of common source connected transistors with sources tied directly to ground to eliminate the Vds overhead usually found in differential pairs. The ground connection minimizes a source resistance noise component, while matching minimizes power supply noise generation and susceptibility for an array of amplifiers. Feedback resistors along with diode connected MESFETS determine the transimpedance of the amplifier. The nonlinearity of diodes helps to soften clipping. Transresistance also determined the noise generated by the amplifier, and the diode connected MESFETS offer lower noise than resistors for the same impedance. Stability is achieved through use of only a single stage of gain in a loop of the input stage, while additional gain is achieved through cascading in the input stage.

Abstract: A power amplification circuit, and a communication device using the same, which are capable of suppressing gain decreases of a power amplifier due to increases in input signal power in a state near the saturation operation, capable of reducing its size, and low in distortion and high in efficiency. The power amplification circuit includes a power amplifier and a negative feedback circuit connected between a signal input terminal and a signal output terminal of the power amplifier. Impedance of the negative feedback circuit depends on a signal voltage occurring across the negative feedback circuit. By adjusting the characteristic that the negative feedback quantity of the negative feedback circuit to the power amplifier is variable depending on input signal power, gain fluctuations of the power amplifier due to increases or decreases of input signal power or output signal power around a specified output signal power are suppressed.

Abstract: According to a level of an input signal, first switching means performs control in such a way that only a first feedback resistor or the first and second feedback resistors become feedback resistors connected to amplifying means, and thereby allows the amplifying means to keep linearity without saturating even when the level of the input signal changes. Furthermore, when the input signal has a higher level than a predetermined threshold, a phase compensation capacitor is charged under the control of second switching means for phase compensation of the amplifying means.

Abstract: In a preamplifier for optical receivers, the input of an inverting amplifier is connected to an input terminal, the output of the inverting amplifier is connected to the gate of a first transistor, the source of the first transistor and the source of a second transistor are connected to a first bias member, the drain of the first transistor and the gate of the second transistor are connected to a first load member, the drain of the second transistor is connected to a second load member and an output terminal, and a feedback resistor is connected between the input and output terminals. With this configuration, a stable, low-power, wide-band transimpedance amplifier is provided without the necessity of special phase compensation.