Abstract: The present invention is related to a filter circuit that allows preamplifiers, such as those used in hard disk drives, to quickly recover from transients such transients caused by power switching, write to read switching, and thermal asperity. According to an embodiment of the present invention, under normal conditions, such as signals at 100 KHz to 10 MHz, signals at medium frequencies, such as signals at 100 KHz to 10 MHz, pass through a low pass filtering circuit. When a transient signal is received, then a change in voltage for Vout of the low pass filtering circuit increases by more than 100*Vout. For example, during transient conditions, the low pass filter circuit may also pass signals ranging from 10 MHz to 100 MHz. Accordingly, under transient conditions, the low pass pole moves approximately 100 times or more. A feedback loop subtracts the resulting low pass signals from the original signal, acting as a high pass filter.

Abstract: The present invention improves the stability and enhances the gain of amplifiers, particularly transistor amplifiers, by using mutual inductive coupling to partially cancel feedback current. Inductors at the input and output of an amplifier are positioned so that a mutual inductance is created between the two inductors. The mutual inductance is used to cancel the inherent capacitive feedback of transistor amplifiers. The use of mutually coupled inductors allows a large value of effective inductance to be obtained by using relatively small inductors. The use of mutually coupled inductors also avoids the problem of low-frequency instability.

Abstract: Apparatus and methods of broadband amplification with high linearity and low power consumption are described. An apparatus configured to amplify a signal includes an input transistor and an output transistor coupled together in a cascode configuration with the input transistor defining an input of the amplifier and the output transistor defining an output of the amplifier. A feedback network is coupled between the input and the output and is characterized by an impedance of substantially zero resistance and non-zero reactance. A method of amplifying a signal is also described. An input signal is received at an input; the input signal is amplified to provide an output signal at an output; and the output signal is sampled at the input through a feedback network characterized by an impedance of substantially zero resistance and ion-zero reactance. A method of making an apparatus configured to amplify a signal is also described.

Abstract: A preamplifier amplifies a differential signal from a magneto-resistive read head. The preamplifier is designed to maximize gain and minimize introduction of noise, while maintaining wide bandwidths and common mode rejection performance. The emitters of the differential amplifier are coupled together by a third transistor and a capacitor.

Abstract: A shunt-feedback technique is provided for improving noise figure and linearity of electronic circuits, such as amplifiers and mixers. An input common-emitter transconductance stage of an electronic circuit has a transistor, and a degeneration impedance provided between the emitter of the transistor and a ground terminal. A feedback capacitor is connected between the collector and the base of the transistor. A feedback resistor is coupled between the collector of the transconductance stage transistor and the emitter of a transistor in the next stage of the electronic circuit. The feedback capacitor and the feedback resistor form a shunt-feedback network.

Abstract: A cascode amplifier which includes a cascade amplifier stage, an output node (coupled directly or indirectly to the cascode amplifier stage), and positive feedback circuitry coupled between the output node and the cascode amplifier stage (or positive feedforward circuitry coupled between the input node and the cascode amplifier stage) for improved amplifier response to rapidly varying input. Preferably, the amplifier is implemented as an integrated circuit or portion of an integrated circuit, and the feedback or feedforward circuitry is configured to reduce rise times and fall times of the output potential (in response to falling and rising edges of the input) to within acceptable limits, with no more than acceptably small overshoot at both the rising and falling edges of the output potential, and with at least substantially equal overshoot at both the rising and falling edges of the output potential.

Abstract: A shunt feedback circuit path for use in high frequency amplifiers fabricated as a transmission line coupled to ground at one end and coupled to the shunt feedback transmission line of the amplifier at the other end. The shunt feedback transmission line has a first and second resistive element and a first and second capacitive element. A quarter-wavelength transmission line is used to transform the impedance coupled to one end with respect to the other end. The impedance as seen from one end of the line is a function of the characteristic impedance of the line. Therefore, by selecting the characteristic impedance the transmission line can be used to affect the impedance of the feedback path so the transmission line appears as an inductor of reactance equal to the characteristic impedance of the quarter-wavelength transmission line and reduces the overall effective length of the feedback path.

Abstract: An apparatus for improving linearity of small signal according to the present invention comprises a least of one non-linear signal generating means for receiving a first DC bias larger than a threshold voltage and for generating a non-linear signal; feedback means for returning the non-linear signal from said a least of one non-linear signal generating means; and amplifying means for receiving, amplifying and outputting to an output unit, a second DC bias larger than the threshold voltage and a reversed and feedback non-linear signal such that the non-linear signal is cancelled. The linearizers according to the present invention have a higher linearity and a simple constitution, and thereby being used for various terminals.

Abstract: The present invention relates to a gain controlled amplifier, and more particularly, to a gain controlled amplifier using active feedback and variable resistance. It is an object of the present invention to provide a gain controlled amplifier minimizing the gain and the degradation of power characteristics generated when adjusting gain in a variable gain amplifier which receives signals having different power levels, amplifies them in accordance with each power level and outputs output signals in a constant power level. In order to achieve the above object, a gain controlled amplifier in accordance with the present invention comprises an amplifier and an active feedback means for negative feedbacking the output of the amplifier to the input of the amplifier, and further has a feedback amount controller inputting the controlled feedback signal to the amplifier by controlling the feedback amount of said active feedback means.

Abstract: An amplifier having error correction and including an output stage containing output transistors being connected to the amplifier output, and an output error correction stage containing a first high open loop gain amplifier which includes one or more transistors being the first high open loop gain amplifier transistor or transistors, an output of which is connected to an input of the output stage, the amplifier including at least two local negative feedback paths, a first local negative feedback path being between an output of the output stage and an input of the first high open loop gain amplifier and a second local negative feedback path being between an output of the first high open loop gain amplifier and an input of the first high open loop gain amplifier.

Abstract: An electric circuit having a switchable feedback branch switchable between a first feedback state, in which the circuit arrangement has a frequency response that is stable with respect to an oscillation tendency, and a second feedback state, in which the circuit arrangement has a frequency response that is unstable with respect to an oscillation tendency. The circuit includes a switchable frequency response compensation circuit which during the first feedback state of the feedback branch can be controlled to an ineffective state and during the second feedback state of the feedback branch can be controlled to an effective state, and in the effective state causes such compensation of the frequency response of the circuit arrangement in the second feedback state that the circuit arrangement in the second feedback state remains stable with respect to an oscillation tendency.

Abstract: An inverting amplifying circuit for outputting an inversion of an input with good linearity, having an inverter circuit, a feedback capacitance, an input capacitance, a first refresh switch, a second refresh switch, a sleep switch, and a first cutoff switch. A sleep voltage is input through the sleep switch to the inverter circuit for minimizing the electrical power consumption. The sleep switch connects a terminal of the inverter circuit directly to ground when in a sleep mode. The first cut off switch is connected between an output of the inverter circuit and an output of the inverting amplifying circuit.

Abstract: An amplifying circuit has a feedback reactance element connected across a biasing feedback resistor and an input terminal for suppressing feedback of thermal noise generated by the biasing feedback resistor.

Abstract: An operational amplifier frequency self-compensated with respect to closed-loop gain comprises a transconductance input stage and an amplifier output stage connected serially together to receive an input signal on at least one input terminal of the amplifier and generate an amplified signal on an output terminal of the amplifier. Provided between the input and output stages is an intermediate node which is connected to a compensation block to receive a frequency-variable compensation signal therefrom. The compensation block is coupled with its input to the input terminal of the amplifier. The compensation block is connected to receive at least the feedback signal. Preferably, the compensation signal is variable as a function of a gain value which is determined by the feedback circuit, and said variation of the compensation signal occurs in a relationship of inverse proportionality to the gain value.

Abstract: A novel device for pole splitting which can be employed in multistage amplifiers having a final stage and a prior stage. The device comprises a first capacitor connected between the output of the prior stage and the output of the final stage, a source follower, and a second capacitor connected between the output of the prior stage and the source follower. The source follower provides an offset voltage that reduces variation of the total capacitance of the first and second capacitors. In a preferred version of the present invention, the first and second capacitor each comprise a MOSFET transistor having a certain threshold voltage. The offset voltage is set to be at least the threshold voltage of the MOSFET transistors. In a preferred version, the source follower comprises a plurality of MOSFET transistors, which includes a MOSFET transistor having a gate connected to the first capacitor and a source connected to the second capacitor.

Abstract: A new class A/F amplifier has an filtering and matching input circuit, a summing junction, an amplifying circuit, a filtering and feedback biasing circuit, and an output filtering and matching circuit. The filtering and matching input circuit responds to a radio frequency access input signal, for providing a filtered and matched radio frequency access input signal. The summing junction responds to the filtered and matched radio frequency access input signal, and further responds to a filtering and feedback biasing signal, for providing a summed, filtered, matched and feedback radio frequency access input signal. The amplifying circuit responds to the summed filtered, matched and feedback radio frequency access input signal, for providing an amplified, summed, filtered, matched and feedback radio frequency access input signal.

Abstract: A current-to-voltage converter with highpass filter function constructed according to the present invention contains two operational amplifiers OP1 and OP2, two resistors R.sub.1 and R.sub.2, and a capacitor C.sub.1. The noninverting (+) terminal of the operational amplifier OP1 is grounded. The inverting (-) terminal of the operational amplifier OP1 is used to receive the output of the current-type sensing device and connected to the output terminal of the operational amplifier OP2 via the resistor R.sub.2. The output terminal of the operational amplifier OP1 is connected to the noninverting terminal of the operational amplifier OP2. The output of the operational amplifier OP2 is fed back to the inverting terminal of the operational amplifier OP2 via the capacitor C.sub.1, and the inverting terminal of the operational amplifier OP2 is connected to one terminal of the resistor R.sub.1 of which another terminal is grounded.

Abstract: A microwave power amplifier is comprised of a plurality of series connected amplifier stages. Each stage is provided with a local negative feedback. The addition of the local voltage feedback distribution networks provide correct voltage distribution and equal current distribution for all transistors, such that the peak-to-peak voltage and current swings of each transistor can be set simultaneously to the values required for efficient amplifier operation. The method applies to both FETs and bipolar transistors. The series connected microwave power amplifier is thus characterized as a stack with local voltage feedback networks which provide an equal distribution of voltage across the transistors in the stack. The amplifier stages can be biased and tuned to collectively operate either as a class A or B amplifier.

Abstract: An stable inverted amplifying circuit includes an odd number of CMOS inverters and a feedback capacitance. Balancing resistances decrease the inverter open gain and limit the gain of the entire circuit. Serial capacitances act to prevent low-frequency oscillation. Oscillation-preventing circuits are also provided to reduce high-frequency oscillation. Sleep, refresh, and sleep-refresh switches are used to cancel residual loads and reduce power consumption.

Abstract: A low noise amplifier includes an input matching means of an input stage and an output matching means of an output stage, a common source transistor and a common gate transistor serially connected between the input matching means and the output matching means, a first inductor connected between said common source transistor and common gate transistor a second inductor connected between the common point of said common source transistor and common gate transistor and the output stage of said common gate transistor. Therefore, the low noise amplifier allows the points of .GAMMA..sub.opt and G.sub.max to be closer to each other so that the noise and input gain simultaneous matching is performed, thereby improving the performance.

Abstract: An MOS FET circuit with a summing circuit at the input of an amplifier to provide charge cancellation. The summing circuit is capacitively coupled to the input with a charge cancellation capacitor. A separate amplifier, having components substantially the same as the components of the first amplifier, is connected through the charge cancellation capacitor to the first amplifier.

Abstract: A low noise RF input amplifier circuit has an input impedance Z.sub.IN for matched-impedance coupling to an antenna having a resistive impedance R.sub.A. The amplifier circuit has an input and output nodes, an inverting amplifier, and a feedback capacitor. The input node receives an antenna signal which the inverting amplifier amplifies by a frequency-dependent gain -A(s) approaching -A.sub.0 at low complex frequencies s. The feedback capacitor C couples the output node to the input node for negative feedback and is selected to match Z.sub.IN to R.sub.A. When the amplifier's gain A(s) has a rolloff approximated by ##EQU1## where p.sub.1 is a negative pole, the capacitance of C which matches Z.sub.IN to R.sub.A is approximately inversely proportional to both (A.sub.0 +1) and R.sub.A.

Abstract: A broad-band amplifier circuit is furnished with a plurality of amplifiers with a coupling capacitor being interposed between every two adjacent amplifiers. Each coupling capacitor has a capacity large enough to prevent adverse effect of external noise. Accordingly, not only the passing of a signal having a low frequency is allowed, but also an element operable in a high frequency, such as a Schottky transistor, can be provided in each amplifier as a transistor. At least the transistor of the amplifier in the last stage is connected to a diode, so that the charges accumulated between its collector and base while the amplifier stays on are fed back and eliminated. Accordingly, the broad-band amplifier circuit can carry out a flat amplifying operation over a wide range from low to high frequency bands, and therefore, can be used for all the ASK method, IrDA1.0 method, and IrDA1.1 method. Consequently, not only the manufacturing cost, but also the size of the broad-band amplifier circuit can be reduced.

Abstract: Various circuit techniques to implement continuous-time filters with improved performance are disclosed. The present invention uses RMC type integrators that exhibit lower harmonic distortion. In one embodiment, a novel high-gain two-pole operational amplifier is used along with RMC architecture to achieve lower harmonic distortion. In another embodiment, the present invention uses dummy polysilicon resistors to accurately compensate for the distributed parasitics of the polysilicon resistors used in RMC integrator. In yet another embodiment, the present invention provides an on-chip tuner with a differential architecture for better noise immunity.

Abstract: An amplifier circuit (20) having independent gain and response time adjustments includes an amplifier (22), a response time resistor (30), a variable gain resistor (32) attached to the response time resistor and to an output of the amplifier (22), a response time capacitor (34) connected in parallel to the response time resistor (30), an anti-gain resistor (36) connected to a response time (30) and variable gain resistor (32) and to ground, and an input resistor (38) connected to the response time resistor (30) and to in input terminal of the amplifier (22). The response time resistor has a substantially greater resistance value than a resistance value of the variable gain resistor (32) for allowing a gain adjustment of the amplifier circuit (20) without changing the response time of the amplifier (22).

Abstract: A reference buffer suitable for driving switched-capacitor or resistive load circuits provides a very low output impedance. The reference buffer utilizes an amplifier with a very large and controlled transconductance configured in feedback and compensated by a load capacitance. Cascaded gain stages are used to provide a large, controlled transconductance. In one embodiment, a reference buffer amplifier includes a plurality of voltage gain amplifiers connected in cascade and at least one transconductance amplifier connected to a last-connected of the plurality of voltage gain amplifiers. The amplifier may further include at least one current mirror amplifier connected to the at least one transconductance amplifier. In another embodiment, the reference buffer amplifier includes at least one transconductance amplifier and at least one current mirror amplifier cascade-connected to the at least one transconductance amplifier. The amplifiers can be differential or single-ended.

Abstract: A low-voltage multipath-miller-zero-compensated operational amplifier is disclosed which includes a class AB front stage and a class AB back stage. The front stage has an inverted input, a non-inverted input, an inverted output, and a non-inverted output. The back stage has an output and input, which input is connected to the non-inverted output of the front stage. The output of the back stage is connected to the inverted output of the front stage. A capacitor is coupled in a feedback loop between the output and inverted input of the back stage. An operational amplifier in accordance with the present invention is particularly well-suited for use in switched-capacitor filters, continuous-time filters, microwave medical applications and general purpose amplification applications.

Abstract: An operational amplifier frequency self-compensated with respect to closed-loop gain comprises a transconductance input stage and an amplifier output stage connected serially together to receive an input signal on at least one input terminal of the amplifier and generate an amplified signal on an output terminal of the amplifier. Provided between the input and output stages is an intermediate node which is connected to a compensation block to receive a frequency-variable compensation signal therefrom. The compensation block is coupled with its input to the input terminal of the amplifier The compensation block is connected to receive at least the feedback signal. Preferably, the compensation signal is variable as a function of a gain value which is determined by the feedback circuit, and said variation of the compensation signal occurs in a relationship of inverse proportionality to the gain value.

Abstract: A two stage operational amplifier circuit comprises a first stage (31) having an input (2, 4) and an output, and a second stage (33) having an input and an output (19). The second stage input is coupled to receive the first stage output. A feedback path (41, 45, 47, 51) is coupled between the output and the input of the second stage. The feedback path (41, 45, 47, 51) comprises a low-frequency compensation path (41, 45) and high-frequency compensation path (45, 47, 51). The feedback path (41, 45, 47, 51) is compensated such that the frequency response of the second output of the second stage is substantially 6 dB per octave throughout the high-frequency region.

Abstract: An integrated operational amplifier with adjustable frequency compensation having a transconductance input stage and an amplifier output stage connected serially together between an input terminal and an output terminal of the operational amplifier. For the purpose of frequency compensation, moreover, a compensation block is connected across the input and the output of the output stage. The compensation block uses a plurality of charge storage elements connected in parallel together and in series with switch block which selects a sub-plurality of said charge storage elements in response to an external signal of the amplifier. The compensation block thereby provides an overall effective capacitance for frequency compensation.

Abstract: A bidirectional amplifier has first and second two-terminal ports each capable of acting as either an input or an output for said amplifier. A field effect type transistor is connected in common gate mode with the common (or grounded) terminal of each of said ports being at least AC connected with the gate of said transistor, and the source and drain of said transistor being respectively connected to a corresponding one of the other terminals of said ports via an impedance matching device.

Abstract: A tuned radio frequency (RF) amplifier includes serially connected input and output common emitter amplifiers with closed ac and dc loops for maintaining high input impedance and low output impedance. The closed ac loop includes a parallel resonant circuit which is connected to the input and capacitively coupled to the output and across which a small signal appears as the difference between the input and output signals. The collector of the input amplifier transistor is maintained at a constant voltage, thereby minimizing any Miller Effect feedback capacitance, and, therefore, any RF degeneration, at the input.

Abstract: A high frequency monolithic amplifier (100) is provided which can be used, for example, in the PLL prescaler of cellular radio systems. The amplifier (100) amplifies single-ended signals having a frequency in the GHz area. It includes a feedback unit (160) which uses parasitic capacitors. The feedback depends on the frequency and is positive for high frequencies and negative for low frequencies. A high gain can be obtained for high frequencies. A comparative low gain a low frequencies prevents the propagation of noise. The amplifier (100) of the present invention can be cascaded to an, for example, 3 stage amplifier arrangement (300).

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

Abstract: An RF power amplifier includes an input-side tertiary harmonic wave control circuit and an output-side tertiary harmonic wave control circuit, respectively connected to a gate and a drain of a signal amplification FET. The RF power amplifier also includes a tertiary harmonic wave feedback circuit connected in parallel with the signal amplification FET. The tertiary harmonic wave feedback circuit includes an input-side tertiary harmonic wave bandpass filter, a tertiary harmonic wave amplification FET, a phase shifter and an output-side tertiary harmonic wave bandpass filter. These circuit elements are connected in series. Due to such a configuration, a voltage waveform and a current waveform each having a nearly rectangular shape can be easily generated at an output terminal (a drain) of the signal amplification FET, not only in the region around the efficiency saturation point whore the FET operates in a non-linear mode, but also in other linear-operation regions.

Abstract: An integrator circuit (10) and a method for generating an output signal that is frequency compensated. The integrated circuit (10) includes an input stage (14) coupled to a transconductance amplifier (11) via a capacitor (13) and a compensation diode (12). The compensation diode (12) provides an impedance that negates an output impedance of the transconductance amplifier (11). The output signal of the integrator circuit (10) is determined by the capacitor (13).

Abstract: A low electric power consumption filter circuit includes an amplifying portion including an odd number of serial MOS inverters. A grounded capacitance is connected between an output of the amplifying portion and ground. A pair of balancing resistances connect an output of the MOS inverter to a supply voltage and ground at a previous stage of the last MOS inverter. A feedback impedance connects an output of the amplifying portion to its input. An input impedance is connected to the input of the amplifying portion.

Abstract: An operational amplifier including reverse amplifiers interconnected in series in an odd number of stages not less than three, an element for feeding back an output from the reverse amplifier in the last stage to an input of the reverse amplifier in a first stage, and a feedback capacitance element provided across the input and output ends of at least one of the reverse amplifiers. The Miller effect makes the feedback current from the capacitance element appear as if it were increased by a factor of the amplification factor of a concerned inverter. Thus, the capacity of the capacitance element preventing the oscillation of the inverters can be reduced. As a result, the operational amplifier becomes highly responsive, and therefore, becomes operable for a high frequency signal.

Abstract: In accordance with the objectives of the present invention, a variety of apparatus and methods for amplifying an electrical signal are disclosed. According to one embodiment of the present invention, a dual-output stage amplifier includes an amplifier stage having an input and an output, a first output stage having an input and an output, a second output stage having an input and an output and an error stage having an input and an output. The first output stage output is coupled with the output of the amplifier stage and responsive to the amplifier stage. If the first output stage output is coupled to an output load, the first output stage is capable of providing an output current to the output load such that a first output voltage related to an input voltage at the input of the amplifier stage is maintained across the output load. In turn, the second output stage input is coupled with the output of the amplifier stage and in parallel with the first output stage.

Abstract: A device for multiplying a capacitance by a variable coefficient, for example for adjusting a cut-off frequency of a filter, includes a current amplifier for amplifying a current flowing through said capacitance. The capacitance is floating between first and second predetermined points. The current amplifier circuit includes a differential current amplifier.

Abstract: A circuit arrangement which has a controllable transmission characteristic between a signal input (2) and a signal output (5) for a signal within a given transmission frequency band, the circuit arrangement having a bass control stage (1) to which the signal from the signal input (2) can be applied for adjustably boosting the amplitude-frequency response of the signal at low frequencies of the transmission frequency band. A higher flexibility and an improved transmission characteristic of such a circuit arrangement are obtained with a simplified construction by a notch filter stage (3), to which the signal processed in the bass control stage (1) can be applied for attenuating the amplitude-frequency response of the signal at mid-frequencies of the transmission frequency band independently of the bass control stage (1) and by which the signal thus processed can be applied to the signal output.

Abstract: A variable-gain amplifying device uses different gains for amplifying an input bias voltage signal, and an input composite signal produced by superposing an input bias voltage signal on an input signal, respectively.

Abstract: A filter circuit that consumes very little electric power. The active filter is a linear inverter constructed by 1) an inverting amplifying portion composed of an odd number of MOS inverters serially connected, 2) a grounded capacitance connected between an output of the inverting amplifying portion and ground, 3) a balancing resistance having a pair of resistances for connecting an output of one of the MOS inverters, other than the last MOS inverter, to the supply voltage and the ground, respectively, and 4) a feedback impedance for connecting the output and input of the inverting amplifying portion. A coupling capacitance is connected to the input of the linear inverter and a plurality of filter circuits are connected to an input of the coupling capacitance.

Abstract: A variable gain amplifier circuit in which a feedback circuit that feeds back the output signal of an amplifier from its output terminal to its input terminal is composed of an FET. The gate terminal of the feedback FET is connected to the output terminal of the amplifier through a capacitor, and the source terminal of the feedback FET is connected to the input terminal of the amplifier. The gain of the amplifying circuit is controlled by varying the transconductance of the feedback FET by controlling a bias voltage applied to the gate or drain terminal of the feedback FET. This makes it possible to control the gain independently of the physical dimension of the feedback FET, and at the same time, to prevent the input signal from being transmitted from the input side to the output side through the feedback circuit.

Abstract: A highly stable linear integrated circuit amplifier (11) is incorporated in a circuit (10) employing transformer (18) feedback providing thermal gain stability determined solely by the transformer turns ratio.

Abstract: An amplifier circuit has a wide frequency range which is broader than the frequency range expected from its circuit parameters. The amplifier circuit comprises a plurality of unit amplifier circuits connected in parallel. Each unit amplifier circuit contains an odd number of inverters serially connected from the first stage to the last stage, an input capacitance connected to the input terminal of the first stage, and a feedback capacitance connecting the output terminal of the inverter of the last stage to the input terminal of the inverter of the first stage. Thus, the amplifier circuit operates in a wide frequency range with little decrease in gain at high frequencies.

Abstract: The invention features an apparatus and technique for amplifying a signal without creating a phase error. The apparatus is an active device with a restricted band width selected to include desired frequencies of operation. The apparatus includes at least one amplifier with a local feedback loop, formed by a network, constructed and arranged to exhibit a high forward gain at the operating frequencies. The amplifier and the network are constructed and arranged to provide substantially 180 degree phase shift between an input voltage and an output voltage at the operating frequencies. The apparatus also includes a signal input node adapted to introduce the input voltage to the inverting input of the amplifier, a signal output node adapted to obtain the output voltage from the output of the amplifier, and a resistive global feedback loop that connects the signal input and signal output nodes and controls the closed loop gain of the amplifying apparatus.

Abstract: The apparatus includes output stage amplifiers for receiving the respective outputs of preamplifiers provided in correspondence to the left and right channels in a stereo system. Negative feedback circuits are provided in the respective output stage amplifiers for reducing the amount of low-band negative feedback. Switch circuits are turned on in response to feedback signals from the respective negative feedback circuits for supplying the feedback signals at the input to the output stage amplifiers.

Abstract: Transimpedance amplifier circuits and methods are provided in which the break frequency of the amplifier is adjusted through a single interface point to the amplifier circuit. At frequencies below the break frequency, the amplifier circuit provides an error current which effectively nulls the output of the transimpedance amplifier so that no output is produced. At frequencies above the break frequency, the break frequency setting element is essentially a short circuit that results in the frequency dependent voltage being substantially zero. This causes the transimpedance amplifier to convert current-to-voltage without signal degradation. The circuit also enables a user to adjust the break frequency without affecting the overall operation of the amplifier. Thus, the amplifier may be coupled to different output circuits for operations in accordance with different communication standards.

Abstract: A method and apparatus for increasing the bandwidth of an operational amplifier and including a capacitor being connected across the inverting and non-inverting inputs of the operational amplifier and further including a feedback circuit connected from the output to one of the inputs, the inverting input, and wherein the value of the capacitance is selected such that the time constant of an RC network including the capacitance and the feedback circuit impedance is proportional to the inverse of the product of the closed loop gain and a factor .beta. which equates the absolute value of the gain at two different frequencies.