Abstract: A negative-feedback amplifier prevents deterioration of the open-loop gain and the distortion improvement effect despite changes in a sending frequency by demodulating a baseband signal from a carrier and an output signal of an amplifier and a demodulated baseband signal. The negative-feedback amplifier includes a correcting member for correcting a phase error of the demodulated baseband signal caused by a delay in the amplifier for each change of a sending frequency of the carrier.

Abstract: A switched capacitor lowpass filter is disclosed having four cascaded general purpose switched capacitor active filter blocks that combine with each other to produce a particular overall transfer function that has high gain selectivity and substantially linear phase response characteristics. The filter can also include a clock input which allows a user to select the cut-off frequency of the filter. The filter's characteristics are tailored in accordance with a method which: (1) introduces a notch frequency into the filter's gain characteristics, so as to improve the filter's gain selectivity near the cut-off frequency, and (2) linearizes the phase response characteristics of the overall filter, without modifying the magnitude of the gain of the notch-containing filter.

Abstract: An audio amplifier having a volume-dependent tone control which is inexpensive and hardly distorts the audio signal. A filter in the signal path of the audio amplifier determines the tone control at low volumes. The bass tones and possibly treble tones are then amplified to a greater extent than the mid-range tones. With an increasing volume, a continuously controllable amplifier stage increasingly compensates this tone control. To this end a linear feedback path is arranged across this amplifier stage, with a pole in or near the frequency range of the bass and mid-range tones.

Abstract: An amplifier, suitable for use in a limited band at microwave frequencies, incorporates a single lossless feedback coupling element between the input port and output port of the gain circuitry. The feedback element is formed of two coextending conductors of a length on the order of a quarter wavelength of the center frequency of the band. An input signal is coupled to the gain element through one of the feedback conductors. An output signal is coupled from the output port of the gain element through the other of the conductors of the feedback element. Relatively low closed loop gain, on the order of 10 dB, is achievable over the specified band at center frequencies on the order of 800-1000 MHz.

Abstract: An embodiment of the present invention comprises a series pass transistor with its emitter arranged to receive a source of DC power, its collector arranged to supply a DC load, and its base connected to the junction of a capacitor to ground and an inductor to the collector. An output capacitor from the collector to ground is alternatively included. In a second embodiment of the present invention, an operational amplifier is inserted in the base circuit to increase the effective circuit gain.

Abstract: An active filter circuit has a filter circuit main part including a first conductance amplifier and a second conductance amplifier in which conductances are each proportional to currents or voltages of control input signals; a first signal generation circuit for generating a current or voltage which corresponds to a first signal; a second signal generation circuit for generating a current or voltage which corresponds to a second signal; a third signal generation circuit for generating a current or voltage which corresponds to a third signal; a first control signal generation circuit for generating a first control signal in accordance with a multiplication of the first signal and a fourth signal which is a ratio of the second signal to the third signal and supplying the multiplication signal to the first conductance amplifier; and second control signal generation circuit for generating a second control signal in accordance with a multiplication of the first signal and a fifth signal which is inverse ratio of t

Abstract: A transimpedance circuit (201), and method therefor, frequency compensates an operational amplifier. The transimpedance circuit (201) has an input terminal (205) coupled to receive an amplified signal (205) and an ouput terminal (206) operative to produce a buffered amplified signal. The input terminal (205) of the transimpedance circuit (201) presents a resistive input impedance to the amplified signal at a frequency substantially near an open loop unity gain frequency of the operational amplifier (200). The amplified signal is buffered from a complex impedance of an input terminal (206) of an output driver (103). The present invention advantageously provides wide bandwidth and stable operation with loads having low complex impedance.

Abstract: A Cartesian amplifier in which an input signal is pre-processed and split into two quadrature components. Both quadrature components are passed, in parallel, through an error amplifier (4), after which they are re-combined and up-converted to RF. The output of the amplifier is used to provide a feedback signal. This feedback is downconverted from RF to baseband and resolved into two quadrature components which are fed to the respective inputs of the error amplifier (4). Periodically the pre-processor (3) is switched into a calibration mode in which test signals are applied to the amplifier instead of the input signal. At these times the signal strength of the output of the power amplifier is measured and used to provide pre-distortion factors in the signal preprocessor (3) to improve amplifier linearity.

Abstract: A circuit for amplifying an input signal comprises an operational amplifi a dual operational amplifier, and a buffering operational amplifier all cascaded in the aforementioned order. The first operational amplifier amplifies the input signal with minimum noise degradation, is set up as a non-inverting amplifier stage, and has a local negative feedback loop comprising a resistor and capacitor in parallel. The dual operational amplifier has two amplifying devices. One device forms a second amplifying stage which increases the gain of the pre-amplified input signal and has a local negative feedback loop comprising a resistor. The other device is a third operational amplifier which combines with the buffering operational amplifier to form an amplifying and buffering stage. The third operational amplifier connects in series to the output of the second amplifying stage.

Abstract: A charge amplifier for sensors outputting electrical charge, particularly for piezoceramic pressure sensors, includes a voltage integrator having an output, an integration capacitor and a resistor connected parallel to the integration capacitor. A current-to-voltage converter is connected upstream of the voltage integrator and has an input. A negative feedback branch has a series circuit of a farther voltage integrator and a voltage-to-current converter. The negative feedback branch is connected between the output of the voltage integrator and the input of the current-to-voltage converter.

Abstract: A power amplifier having a gain factor of G for generating an output signal from a low power amplitude and phase modulated input signal. The power amplifier generates first and second constant envelope signals. Each constant envelope signal has the same frequency as said input signal. The first constant envelope signal has the same amplitude as the second constant envelope signal but differs in phase from the first constant envelope signal by an amount depending on the amplitude of the input signal. The output signal is generated by vectorially adding the first and second constant envelope signals. The amplifier has a feedback loop which operates by determining the difference in amplitude between the input signal and a signal having an amplitude 1/G times the amplitude of the output signal. The phase difference between the first and second constant envelope signals is altered so as to reduce the determined difference in amplitude.

Abstract: A combined programmable gain and integrating amplifier comprises an operational amplifier having an inverting input terminal coupled to a reference voltage. A plurality of capacitors are selectively connectable in parallel between the inverting input terminal and the amplifier output terminal. At least one terminal of each capacitor is connected to the inverting input terminal. A plurality of controllable switches are connected in series circuit between a corresponding one of the capacitors and the amplifier output terminal for coupling the capacitors in circuit between the inverting input terminal and the output terminal. In a first operational state, each of the switches connects the capacitors between the input and output terminals. In a second operational state, the switches connect selected ones of the capacitors the reference voltage.

Abstract: A power controller includes a closed-loop system having a summer to sum an input signal with a derived output signal to produce a difference signal. A comparator compares the difference signal with a reference signal to produce a digital signal representative of the polarity difference between the difference signal and the reference signal. Two switching networks respond to the digital signal to produce high energy outputs representative of the digital signal which are used to reduce the level of the difference signal in a frequency band of interest at the comparator. A low pass filter between the high energy outputs and the comparator attenuates high-frequency noise. A low-pass filter of at least the third order, connected in the closed loop, enhances the signal-to-noise ratio. In a specific application the power controller is a power amplifier and the input signal is in the audio frequency range.

Abstract: A method and apparatus is provided for controlling peak envelope power level in a power amplifier (PA) (10). The method includes the steps of measuring (101) a first peak envelope power value of an input of the PA during a first time period, comparing (102) the first peak envelope power value with a threshold value, and introducing a phase change (103) into a selected signal of a plurality of signals being amplified by the PA when the first peak envelope power value exceeds the threshold. The method further includes measuring (104) a second peak envelope power value during a second time period, comparing (105) the first and second peak envelope power values, and reversing (106) the phase change to the selected signal when the second peak envelope power value exceeds the first peak envelope power value.

Abstract: An active filter having a frequency characteristics of the fewer variations of manufacturing and the least temperature dependency is provided. A differential amplifier is comprised of resistors 15 and 16 which have a resistance value R.sub.E and are connected in common to a current source 39 in proportion to kT/(qR.sub.0), together with transistors 13 and 14. The transistor 14 is connected to an active load comprised of transistors 18 and 19. The transistor 18 is connected to a current source 31 for producing a current in proportion to a capacity C.sub.0 while the transistor 19 is connected to a current source 30 for producing a current of a remainder of the current produced by the current source 31 subtracted from the current in proportion to 1/R.sub.a. The transistor 19 is further connected to an internal capacitor 21 having capacity C.sub.1. A frequency characteristics of the active filter circuit is determined by the ratio of resistance values R.sub.E, R.sub.0 and R.sub.

Abstract: A polar leapfrog filter includes at least one polar network. The polar network comprises a differentiator constituted by an operational amplifier having input and output terminals, and a first integrator formed by a first capacitor for providing negative feedback to the operational amplifier and a first variable transconductance amplifier; and a second integrator formed by a second capacitor for providing negative feedback to the first integrator, and a second variable transconductance amplifier. A differentiator is provided at each of the input and output portions of the filter, and a third differentiator is provided immediately preceding the output side differentiator. In the case where two or more said polar networks are incorporated, an additional differentiator is provided between the polar networks. The sum of the number of the circuits constituting the differentiators and the number of the polar networks is selected to be even and equal to the order of the filter.

Abstract: A polar leapfrog filter includes at least one polar network. The polar network comprises a differentiator constituted by an operational amplifier having input and output terminals, and a first integrator formed by a first capacitor for providing negative feedback to the operational amplifier and a first variable transconductance amplifier; and a second integrator formed by a second capacitor for providing negative feedback to the first integrator, and a second variable transconductance amplifier. In the case where two or more said polar networks are incorporated, an integrator is provided between adjacent ones of the polar networks. The total number of all the circuits is selected to be odd and equal to the order of the filter. The adjacent ones of the circuits are connected in such a manner that leapfrog type negative feedback is effected.

Abstract: A polar leapfrog filter includes at least one polar network. The polar network comprises a differentiator constituted by an operational amplifier having input and output terminals, and a first integrator formed by a first capacitor for providing negative feedback to the operational amplifier and a first variable transconductance amplifier; and a second integrator formed by a second capacitor for providing negative feedback to the first integrator, and a second variable transconductance amplifier. An integrator is provided at each of the input and output stages, and a third integrator is provided immediately preceding the output side integrator. In the case where two or more said polar networks are incorporated, an additional integrator is provided between the polar networks. The total number of all the circuits is selected to be even and equal to the order of the filter.

Abstract: A limiter amplifier includes amplifiers connected in cascade each having differential outputs and differential inputs, and a lowpass filter connected between adjacent amplifiers. The filter includes resistors having different values connected between the differential outputs and the differential inputs of adjacent amplifiers, and a capacitor connected between the differential inputs of one of the adjacent amplifiers, the filter thereby limiting a high frequency characteristic of the limiter amplifier.

Abstract: An all-pass filter includes an adder which comprises a variable conductance amplifier and a capacitor connected to the output terminal thereof. The adder is being arranged to add the output of a band pass filter and an input signal together.

Abstract: An apparatus for generating an amplified signal from an input signal. The apparatus comprises: (a) a phase-shifting circuit for shifting the phase of a feedback signal derived from the amplified output signal in response to a control signal; (b) a differencing circuit for generating an output signal based on the input signal and the phase-shifted feedback signal; (c) a filter for filtering the output signal; and (d) a power amplifier for amplifying the filtered output signal to obtain the amplified output signal. The apparatus further comprises a CPU and DAC for generating a control signal corresponding to a control signal value associated with a frequency range including the operating frequency from a table associating predetermined control signal values with frequency ranges in the portion of the frequency spectrum in which the amplifier is designed to operate. Phase shift introduced by the filter is thus compensated for by the phase-shifting circuit to maintain negative feedback and thus system stability.

Abstract: A power amplifier arrangement includes a power divider for dividing the signal to be amplified into equal-amplitude components. Each component is amplified by a signal amplifying path. The amplified signals are applied to a phase-sensitive power combiner. The combined signal appears at the sum port and a phase-related difference signal appears at a difference port of the combiner. The difference signal is processed to produce a control signal for controlling the relative phases of the signals passing through the signal amplifying paths.

Abstract: In a circuit arrangement with a electronically controllable transfer characteristic, the input signal is applied to an amplifier with a controllable negative feedback. The amplifier has its output connected to a voltage-divider circuit having a frequency-dependent characteristic. This circuit has a plurality of taps (9 to 13, 31 to 35) which are connected to an inverting input of the amplifier via a first electronically controllable switch (8) and to the output of the arrangement via a second electronically controllable switch (30). The two switches (8, 30) are controlled in a manner so as to influence the Q-factors of different filter curves. Therefore, in order to boost the input signal in a frequency band determined by the frequency-dependent voltage divider, the first switch (8) is set a position such that boosting is effected with the desired frequency bandwidth. Furthermore, the position of the second switch (30) is selected so as to obtain boosting to the desired degree.

Abstract: A monolithic operational amplifier (10) having an Miller loop compensation network (13) with improved capacitive drive. The monolithic operational amplifier (10) has an input stage (11), an output stage (12), and a compensation network (13). The compensation network (13) provides negative feedback between an output node (19) of the output stage (12) and an input node (16) of the output stage (12). The compensation network (13) has a compensation capacitor (26), a resistor (27), an isolation resistor (33), a shunt capacitor (28), and an isolation transistor (25). The compensation network (13) creates a dominant pole, a zero and a nondominant pole having a higher frequency than the zero. The nondominant pole improves a gain margin while preserving sufficient phase margin. The isolation transistor (25) provides improved capacitive drive.

Abstract: An active filter comprises a differential-type voltage-controlled current source. A first resistor is connected between the first input terminal of the voltage-controlled current source and a first signal source. A second resistor is connected between the second input terminal of the voltage-controlled current source and the second signal source (or the output terminal of the voltage-controlled current source). The incremental transfer conductance gm of the filter becomes smaller by R.sub.2 /(R.sub.1 +R.sub.2) compared to that of an active filter which does not contain the first and the second resistors of the active filter of the invention, where R.sub.1 and R.sub.2 are resistance values of the first and the second resistors, respectively.

Abstract: A head amplifier is integrated into an IC with a minimum number of pins and outside parts as well. An offset cancellation circuit cancels offset voltages to prevent distortion of playback signals. An amplifier amplifies a playback signal to produce an output signal that is fed to one input of a differential amplifier. A reference voltage is fed to the second input of the differential amplifier. The input of the differential amplifier is compared in a comparator with the reference voltage to produce a feedback signal for cancelling offset voltages. The feedback path is frequency sensitive to reduce frequency response at low frequencies, and to compensate for distortions produced at high frequencies from using PNP transistors in the comparator.

Abstract: A polar leapfrog filter includes at least one polar network. The polar network comprises a differentiator constituted by an operational amplifier having input and output terminals, and a first integrator formed by a first capacitor for providing negative feedback to the operational amplifier and a first variable transconductance amplifier; and a second integrator formed by a second capacitor for providing negative feedback to the first integrator, and a second variable transconductance amplifier. A differentiator is provided at each of the input and output stages of the filter. In the case where two or more said polar networks are incorporated, an additional differentiator is provided between the polar networks. The total number of all the circuit units constituting the filter is selected to provide odd order and equal order for the filter. The circuit units are connected in such a manner that leapfrog type negative feedback is effected.

Abstract: An active filter circuit comprises a differentiator constituted by an operational amplifier having an input terminal and output terminal, and a first integrator constituted by a first capacitor and a first variable conductance amplifier for providing negative feedback to the operational amplifier and a first variable conductance amplifier; and a second integrator constituted by a second capacitor and a second variable conductance amplifier for providing negative feedback to the first integrator. The active filter circuit is arranged such that a damping pole is set up at a predetermined frequency by adjusting operating currents of the first and second variable conductance amplifiers.

Abstract: A phase shifting circuit includes: a pair of input terminals; a pair of output terminals; a variable gain amplifier and an active alternating current integrator, connected in series between the input terminals and the output terminals; and a control circuit for controlling the gain of the amplifier in dependence on the voltage between the input terminals and the voltage between the output terminals so as to maintain the amplitude of the voltage between the output terminals substantially equal to the amplitude of the voltage between the input terminals. The phase shifting circuit exhibits low variation of phase shift with input signal frequency.

Abstract: A r.f. wideband high power amplifier (1) receives an input signal at its input via a coupler (7) whenever a signal for amplification is applied to an input port (15). The output of the amplifier (1) is tapped by a coupler (8) and fed to an input of a comparator (3). The input signal applied at the input port (15) is fed to a second input of the comparator (3) via a delay line (5), arranged to introduce a delay substantially equal to that of the power amplifier (1). The comparator (3) produces at its output an error signal representative of the difference between the input signal fed via the amplified and the delayed path. A combiner (16) serves to introduce the amplified error signal to the amplifier output signal such that the error signal is in anti-phase therewith. Thus, the resultant signal produced at an output port (4) has had feed forward distortion cancellation.

Abstract: A multi-stage amplifier utilizes capacitive nesting of three or more amplifier stages in combination with multiple feed-forward paths to achieve frequency compensation. Two stages (A.sub.M and A.sub.O) in cascade are first nested with a pole-splitting capacitor (C1) to form a stable device. A stable three-stage amplifier is then created by nesting the two-stage device and a further stage (A.sub.I) with another pole-splitting capacitor (C2) where feed-forward paths are provided from the further stage to both of the other stages.

Abstract: A high frequency amplifier circuit comprises an amplitude characteristic correction circuit and a phase characteristic correction circuit for compensating the non-linearity of the input-output characteristics of the amplifier. The amplitude characteristic correction circuit varies the drain voltage or the collector voltage of the amplifier in accordance with the envelope level of an input signal in such a manner that the relationship between the amplitude of the output of the amplifier and the amplitude of the input signal has linearity. On the other hand, the phase characteristic correction circuit provides a quantity of phase shift to the input signal in accordance with the envelope level of the input signal, and the phase-shifted input signal is applied to the amplifier in such a manner that the phase of the output of the amplifier and that of the input signal coincide with each other.

Abstract: A leapfrog filter comprises a first integrator made up of a first operational amplifier and a first capacitor connected to output terminal of the first operational amplifier; a second integrator made up of a second operational amplifier and a second capacitor connected to inverting input terminal and output terminal of the second operational amplifier; and a variable current source circuit. The first operational amplifier has the output terminal thereof connected to non-inverting input terminal of the second operational amplifier. The second operational amplifier has the output terminal thereof connected to inverting input terminal of the first operational amplifier. An input terminal is connected to non-inverting input terminal of the first operational amplifier; and output terminal connected to the output terminal of the second operational amplifier.

Abstract: A high frequency SSB radio transmitter has an envelope amplitude modulator for varying the envelope of an r.f. signal source based on an error signal from envelope detectors detecting the envelope of the input and output waveform. It also has a first phase modulator in a main feedback loop for varying the phase of the input waveform based on differences detected in a phase detector between the instantaneous phase of the input and output r.f. signal. To overcome the problem of spurious outputs from the phase detector resulting from the cross-over points of the SSB waveform when there are carrier breaks and other problems, a subsidiary, phase lock loop feeds a signal derived from the error signal to a second phase modulator to tend to hold the inputs to the phase detector in such a phase relationship that the output is zero. To cope with large phase shift errors between the input waveform and the output which result when the power amplifier changes frequency or temperature variations e.g.

Abstract: A photoelectrical sensor (10) provided with a multistaged, filtered amplifier circuit (16) for amplifying voltage pulses from a phototransducer (12) and a filtering I/V converter (14) includes three voltage amplifier stages (28, 30, 32) and three respectively associated band pass filters (34, 36 and 38) for cascade connecting the amplifier stages (28, 30, 32) between the phototransducer (12) and the detector circuit (18) and accumulating attenuation of response to signals at a frequency equal to the frequency of full wave rectified AC line voltage to maximize desensitization of the photoelectrical sensor (10) to AC powered ambient light fluctuations while broadening the pass band at the low frequency end for maximum response to the desired signal. A gain control circuit (40) is associated with the first stage amplifier (28), while a temperature compensation circuit (42) adjusts the gain of a second stage amplifier stage (30) to correct for temperature variations.

Abstract: An analog active filter for realizing the secondary transfer function by using an amplifier having a feedback loop having a first integrating function block which integrates an input signal, second and third integrating function blocks which integrate an output signal, a first signal combining function block which combines signals from the first and second integrating function blocks with the input signal, a fourth integrating function block which integrates signals from the first signal combining function block, and a second signal combining function block which combines signals from the third and fourth integrating function blocks with the input signal and derives the output signal.

Abstract: A balanced filter circuit includes only one balanced amplifier (10) having an inverting input (6) and a non-inverting input (5) and an inverting output (7) and a non-inverting output (8) for realization of filter transfer functions Uout/Uin of the second or higher order from an input signal Uin at input terminals (1, 2) to an output signal Uout at output terminals (3, 4) having passive admittances which are composed of a parallel-combination of a resistor (R42, R44) and/or a capacitor (C41, C44) and/or a number of series-combinations of a resistor (R41, R43, R45) and a capacitor (C42, C43, C45).

Abstract: A closed loop RF power amplifier output correction circuit is disclosed, for providing closed loop continuous amplitude and phase correction of solid state amplifiers. The circuit includes a two channel RF solid state high power amplifier whose inputs are fed through two control phase shifters and whose outputs are combined in a hybrid junction. A reference signal is provided, which the power amplifier must duplicate in amplitude and phase. A coupling and comparision circuit compares the reference signal and the amplifier output signal and provides an error signal representative of error power. Digital circuitry is provided which takes only relative error power measurements and nulls the error by adjusting the control phase shifters in a closed loop.

Abstract: The filter comprises at least one completely differential operational amplifier having two inputs and two outputs and at least one pair of feedback circuits connecting said outputs with respective inputs of said amplifier outside of same. The operational amplifier has no common-mode feedback circuit, whose functions are performed by said feedback circuits external to the amplifier.

Abstract: The present invention relates to a device for correcting the phase induced by the class C operation of a solid state amplifier. It is applied in the field of the manufacture of pulse radar transmitters. Solid state amplifiers are prone to generating phase variations. The invention relates to a measurement and correction loop which allows the real time elimination of phase variations due to heating up.

Abstract: A linear transmitter having both an open loop and a closed loop training mode capability functions to schedule and facilitate these training modes in a manner that reduces adjacent channel splatter. A training waveform can be utilized to enhance these operational objectives. Scheduling of the open loop and closed loop training modes can be ordered, in a TDM system, in a variety of ways.

Abstract: A balanced filter circuit has a number of balanced pushpull amplifiers (10) whose inputs (11, 12) and outputs (13, 14) are coupled to filter resistors (20, 21, 22, 25, 27A/B) and filter capacitors (23, 24, 26A/B). In order to adjust the filter, the currents from the filter resistors to the inputs of the balanced amplifiers are varied by means of adjustable balanced multipliers (40).

Abstract: A single-ended input to differential output amplifier performs a predetermined transfer function on an input signal substantially independently of nonlinearities in component values. The input signal and a first reference voltage are coupled to a circuit network, which is coupled to a fully differential operational amplifier, to implement the predetermined transfer function. A common mode voltage between positive and negative output signals of the operational amplifier is sensed and fed back to the operational amplifier so that the operational amplifier may set the common mode voltage to a second reference voltage. The circuit network has first, second, and third capacitors, the third capacitor coupled between a positive input terminal and the first reference voltage.

Abstract: A high precision composite amplifier for use in a data acquisition subsystem of a Computerized Tomography (CT) scanner provides enhanced high speed response in terms of reduced settling time. The speed improvement is due to a novel compensation network in which a high frequency pole and a zero in the open loop response characteristic for the composite amplifier are forced to cancel despite component and temperature variations. The resulting amplifier exhibits a simple, higher speed, single pole response. An adjustable circuit is provided for adjusting the placement of the zero to assure optimum pole/zero cancellation.

Abstract: A leapfrog filter comprising a first and a second integrator each consisting of an operational amplifier and integrating capacitor. The leapfrog filter includes differential amplifier which is arranged to differentially supply current to the first and second integrators through a first and a second current source circuit respectively; and a third current source circuit for adjusting the sum of currents supplied to the first and second current source circuits, wherein characteristics such as the center frequency f.sub.o and quality factor Q of the leapfrog filter are controlled by adjusting the respective current values.

Abstract: A transceiver module includes a bi-directional amplifier having a pair of symmetric signal paths for amplification of both transmit and receive signals is described. The amplifier is a bi-directional amplifier and includes a pair of symmetric signal paths. The amplifier is disposed between a pair of r.f. switches to provide a pair of signal paths between two terminals of the module. A phase shifter is coupled between on of the terminals of the module and one of the r.f. switches, wherein the second terminal of the module is coupled directly to the other one of the pair of switches.

Abstract: An amplifier circuit is described comprising a transconductance amplifier in series with a voltage gain stage. A compensation capacitance coupled across the voltage gain stage includes a capacitance whose value is dependent upon the output voltage of the voltage gain stage so as to optimize amplifier stability over a wide range of output voltages.

Abstract: A charge amplifier circuit comprising an operational amplifier unit whose signal output is back to a signal input of the amplifier unit via a capacitative feedback element, the signal output of the operational amplifier unit also being coupled to an input of a following, further transmission unit that has a proportional, integrating transfer characteristic with a break-over frequency that is at least approximately equal to the break-over frequency of the operational amplifier unit, this being at least in the proximity of the break-over frequency defined by the feedback element of the operational amplifier unit. The feedback element of the operational amplifier unit can be optimized independently of the operating frequency range, this, allowing for a low resistance value for the feedback element given a transfer behavior that remains linear, this despite the low capacitor value that increases the charge sensitivity.

Abstract: A current amplifier including two stages. A first stage is formed by a primary operational amplifier (IC1) connected in a virtual earth feedback configuration and having a feedback loop formed by a resistor (R1) and capacitor (C1) connected in parallel so that the primary operational amplifier has a frequency response up to a predetermined frequency and thereafter the frequency response rolls off at a predetermined rate. A second stage including another operational amplifier (IC2) connected in a virtual earth or non-inverting feedback configuration having a frequency characteristic chosen to provide in combination with the frequency characteristic of the primary amplifier a desired operating range for the amplifier.

Abstract: A general biquadratic filter circuit is described which uses operational transconductance amplifiers. A bias current controls the transconductance (gm) of the amplifiers which in turn control the corner frequency (Wo) of the circuit. The circuit is configured with three potential sources which can be preselected to either be at a ground level or at a desired voltage level. By preselecting which of the potentials are grounded and which are at a desired voltage level, the circuit can become either a lowpass, highpass, bandpass or notch filter.