Abstract: A volume control circuit for hearing aids is adjustable to vary a control signal supplied to an amplifier between a microphone and receiver of a hearing air. The volume control circuit includes a positive voltage source, a charge holding circuit, and a switch for alternatively connecting the holding circuit with the positive voltage source to increase its voltage, with ground to decrease voltage, and with an open circuit to maintain a constant voltage. The holding circuit voltage is inverted around a predetermined reference voltage level, with the inverted signal amplified and applied to the gate terminal of an n-channel field effect transistor having its source terminal biased to a predetermined source voltage level, and its drain terminal electrically connected to the amplifier to provide the control signal. In response to charging of the holding circuit, the gate voltage is reduced to increase the FET impedance, thus decreasing the gain of the amplifier.

Abstract: A system for the high gain amplification of musical audio signals uses a control signal derived from the audio signal to automatically vary the current in the gain control circuit of the amplifier in response to audio signal level changes. A distortion circuit in the feedback path of the amplifier provides controlled distortion. The system may also provide for a variable control signal threshold level and for variation in control signal decay characteristics. The system may further provide a user variable maximum gain control.

Abstract: An automatic gain control circuit for an amplifier operating over a prescribed frequency range detects the output level of the amplifier; and couples a repeated predetermined waveform occurring at a rate greater than the reciprocal of twice the upper frequency of the prescribed frequency range to the output level signal. The waveform varying level signal is compared to a reference threshold to control the gain of the amplifier through a switched resistive elemement in the amplifier feedback path. The repeated waveform variations about the amplifier output level causes the value of the switched resistance to vary as a function of the output level. A low pass filter connected to the amplifier output removes switching transients resulting from the high frequency changes in the switched resistive element. The gains of a plurality of amplifiers may be determined by a common control for accurate tracking over a wide dynamic range.

Abstract: A circuit arrangement has a pre-amplifier that has its input connected to an opto-electric transducer and whose gain is controllable by a final control element formed by a field effect transistor. In order to achieve an especially great range of dynamics, the pre-amplifier contains the drain-source path of a field effect transistor that is connected in parallel to a resistor in a feedback branch. This field effect transistor is activated or inhibited by a regulator. In this way, the range of control of a controllable amplifier arrangement following the pre-amplifier is doubly utilized. The circuit arrangement can be advantageously used in optical transmission equipment of PCM technology.

Abstract: An amplifier arrangement with controllable gain comprising two differential amplifiers which are connected in parallel at their inputs and outputs and which have different gain factors which can be varied oppositely. The gain of one of said differential amplifiers is reduced in that a first resistor is connected between its input terminals and a second resistor is connected between at least one of said input terminals and the corresponding input terminal of the other differential amplifier. As a result, the input signal to this amplifier is subject to a voltage division enabling the input swing to be increased.

Abstract: A switchable gain circuit includes an operational amplifier (10) which has an input leg comprised of a series resistor (20) and an MOS transistor (22). A plurality of feedback legs are formed, each comprising one or more resistors that are equal in value to the input resistor (20), and connected in series with a switch transistor. The proportion of the series resistance of the transistor in a given feedback leg to the series resistance in the transistor in the input leg is equal to the proportion of the fixed resistance in the feedback leg and input leg. The value of the series resistance of the feedback transistors therefore factors out the series resistance of the input transistor (22) in the gain calculation. This significantly reduces harmonic distortion in the output signal.

Abstract: An output stage with automatic level control for power line signalling, including a controlled amplifier (F.sub.1) and a feedback circuit for sensing the output voltage (V.sub.0 +V.sub.0) of the output stage and for supplying a control signal (v.sub.4) to a control input of the controlled amplifier (F.sub.1). The feedback circuit includes a comparator (K) for comparing an alternating voltage (v.sub.1) which is responsive to the alternating voltage component (v.sub.0) at the output stage and which is furthermore superposed on a first direct voltage (V.sub.1) with a second direct voltage (V.sub.2). As control signal to the controlled amplifier (F.sub.1) there is utilized the voltage (v.sub.4) across the capacitor (C.sub.4), the voltage of which increases or decreases in response to the comparison result of the comparator (K).

Abstract: To correct temperature caused changes in symmetry and gain in a voltage controlled amplifier including a logarithm circuit and an antilog circuit, an auxiliary voltage proportional to the absolute temperature is provided to control the antilog circuit; this auxiliary voltage is also contained as a factor in a voltage which controls both the logarithm and the antilog circuits.

Abstract: A device is provided for amplifying and sampling signals in an acquisition chain before application thereof to an analog-digital converter and in particular multiplexed signals. It includes two blocking samplers to which a gain of 1, 2 or 16 for the first one and a gain of 2 or 16 for the second one may be applied by selective closure of switches. A switch allows either the input signal or the signal from the second sampler to be applied to the first sampler. Another switch allows the outputs of one or other of the samplers to be connected to the input of a voltage comparator. By a very limited number of comparison steps, gain modifications and possible relooping of the output to the input of the device for one or more reamplifications, an input signal may be given any gain between 2.sup.0 and 2.sup.13.

Abstract: A very wide bandwidth, wide dynamic range amplifier incorporating a plurality of feedback paths which are parallel connected upon command is illustrated. The parallel connection is actuated from an input signal strength sensor which has built-in hysteresis so that there is no continuous switching from one feedback configuration to the other at a given input signal strength. The design of the switch feedback path is such that there is very low capacitance at the input of the amplifier, and a single signal peaking compensation circuit can be used to prevent undesirable signal peaking in the response curve.

Abstract: An equalizer circuit for equalizing a signal attenuated in frequency while the same is transmitted through a transmission line and eliminates out-band high frequency noise so as to provide a signal having flat frequency characteristics. The equalizing circuit includes a high-pass circuit, a Sallen-Key low-pass circuit capable of gain regulation, constructed by connecting the output terminal of an operational amplifier through a resistance to the negative input terminal of the same and grounding the negative input terminal through a variable resistance, an amplifying circuit capable of gain control for amplifying a signal supplied to the positive input terminal of the operational amplifier of the Sallen-Key low-pass circuit, and a control circuit which detects the peak level of the output signal of the amplifying circuit and controls the resistance of the variable resistance of the Sallen-Key low-pass circuit and the gain of the amplifying circuit on the basis of the result of the detection.

Abstract: A circuit arrangement for converting an input voltage into a proportional ouput signal, including a converting resistance which is followed by operational amplifier having a feedback resistance. For the purpose of stabilizing the gain of the circuit arrangement with respect to changes in the converting resistance, the latter is formed by connecting two branch resistances in parallel with each other. These branch resistances are series-connected in a bridge circuit to which a direct voltage is supplied from a voltage source. The bridge circuit also includes an operational amplifier and high-quality film resistors and a variable balancing resistance which includes, in series, another film resistor and a field effect transistor. An integrator automatically balances the bridge circuit by controlling the field effect transistor. The balancing resistor.

Abstract: An amplification gain adjusting circuit in which the gain of an AC amplifier is controlled by a voltage dividing series connection of two resistors. One of the resistors is selectively shorted by a switching transistor. The DC bias of the switching transistor is set to prevent current flow through the base of the switching transistor at high AC levels.

Abstract: A multichannel predictive gain amplifier system including a device for receiving input from a first channel and from a second channel, a variable gain amplifier, and a gain setting circuit for setting the gain of the variable gain amplifier. A switching device responsive to the input from the first and second channels sequentially connects each channel first to the gain setting circuit for determining the desired gain for that channel and then to the variable gain amplifier set to that desired gain.

Abstract: A low impedance interface circuit for use with an internal combustion engine between a capacitive piezoelectric combustion pressure sensor and LPP signal processing circuitry comprises an operational amplifier with a negative feedback capacitor and an input DC blocking capacitor, a voltage follower amplifier with a first resistor at its input and a second resistor at its output connecting it in parallel with the feedback capacitor, a DC filter capacitor connected to the input of the voltage follower amplifier and forming a low pass filter with the first resistor to maintain a substantially constant DC voltage equal to the DC operating voltage for DC feedback, a current source controlled by the output of the operational amplifier and connected in series with the first resistor to provide increased current for the charging of the DC filter capacitor and a diode bypassing the first resistor to allow fast charging of the DC filter capacitor and DC blocking capacitor during startup.

Abstract: An improved instantaneous floating point (IFP) amplifier is provided having a plurality of cascaded amplifier stages, with each stage having a plurality of possible gains. The input sample signal is passed through each stage so that no stage is selectively bypassed.A bipolar, logarithmic amplifier is used for gain control. The gain control bits correspond to the industry standard gain control codes, thereby eliminating the need for bit mapping.The offset voltage control circuit is initialized during power-up by removing the IFP input signal and measuring the input referred offset at each gain setting. The measurements are stored. When a sample signal is received at the IFP amplifier input, the appropriate gain is applied to that signal along with the stored offset value corresponding to that gain.

Abstract: A method and apparatus are described for converting variations in a measured variable (such as pressure) to corresponding variations in an electrical output signal. The preferred method utilizes a capacitive sensor whose capacitance changes to reflect changes in the measured variable. The changes in capacitance are preferably used to vary the gain of a switched-capacitor amplifier whose signal input receives a relatively constant DC reference voltage. The amplifiers' output may be sampled and further amplified to provide an output signal which is indicative of the value of the measured variable.

Abstract: A variable gain amplifier of the logarithmically linear type comprises a divider for dividing a signal applied to the input terminal of the amplifier by a gain control signal. The output of the divider is applied to a first input of a subtractor, the second input of the subtractor being connected to receive the signal applied to the amplifier's input terminal to deliver a signal to the output terminal of the amplifier. The amplifier has an input-to-output characteristic given by (2.sup.n /x)-1 which is approximated to exp{2-x/(2.sup.n-2)}, where x represents the gain control signal.

Abstract: The remote control system having symmetrical signaling circuits for radio communications is coupled to a single wire line/audio channel and permits two or more units, base stations and/or remote consoles, to be coupled to the single wire line. Each signaling circuit comprises a wire line coupler for coupling to the wire line, an audio input line and an audio output line. An automatic gain control circuit is coupled between the wire coupler and the audio output line and a filter and line driver are coupled between the audio input line and the wire coupler. A control unit including a microprocessor, a tone encoder, a tone decoder, a timer, a clock, and a memory is coupled by output lines to the automatic gain control circuit for controlling the modes of operation thereof which include a slow decay mode, a fast decay mode, an adapt mode and a hold gain mode. The output from the gain control circuit is also routed through a band pass filter and a limiter to the control unit.

Abstract: A feedback amplifier circuit includes an inversion circuit, a level shift circuit, and a feedback resistive element. The inversion circuit includes an input active element and a load element connected in cascade with respect to a voltage source. The level shift circuit includes a field effect transistor having a gate connected to the output of the inversion circuit, a diode or diodes, a constant current active load connected in cascade with respect to the voltage source, and the feedback resistive element is connected between the output of the level shift circuit and the input of the inversion circuit.

Abstract: A transimpedance amplifier for data signals from a high impedance source includes a forward voltage amplifier and a feedback resistance. The feedback includes an FET. The resistance of the FET is controlled by a control signal derived from the data signal at the output of the transimpedance amplifier by a differentiator which generates pulses for each data transition and an average detector which generates a control signal responsive to the number of transitions per unit time, which is the data rate. The resistance of the FET is high when the data rate is low, reducing the noise magnitude and decreasing the noise bandwidth. When the data rate increases, the resistance of the FET decreases, providing greater bandwidth for handling the signal. The change in gain caused by the bandwidth control tends to change the magnitude of the output data signal. This may be corrected by an AGC loop which controls the open loop gain of the voltage amplifier.

Abstract: A high input impedance circuit having a first differential circuit consisting of a pair of NPN transistors and a second differential circuit consisting of a pair of PNP transistors, is disclosed. One input terminal of the first differential circuit is connected to one input terminal of the second differential circuit. The other input terminal of the first differential circuit is connected to the other input terminal of the second differential circuit. A signal is supplied through a capacitor to one input terminal for eliminating a DC component of the signal. A DC biasing circuit for biasing the first and second differential circuits is connected to the other input terminal. First and second current source circuits are connected to the first and second differential circuits respectively.

Abstract: A high accuracy selectable gain instrumentation amplifier system which avoids amplifying signal distortions produced by gain selection switches includes a high gain amplifier having an input coupled to receive a system input signal and a feedback signal and an output generating an output signal proportional to the difference therebetween, a feedback network providing a plurality of gain selection feedback paths to the amplifier input, a first switching network coupling the amplifier output to a selected feedback path and a second switching network coupling the selected feedback path to the system output. The amplifier system may be implemented in either a differential or single ended ground referenced configuration.

Abstract: A three-mode analog controller for regulating a signal corresponding to a controller variable to produce a controller output, comprises an integrating circuit, a proportional circuit, and a derivative circuit. The integrating circuit includes a reset adjustment for varying a time constant thereof, the proportional circuit includes a gain adjustment for varying the gain thereof and the derivative circuit includes a rate adjustment for adjusting the rate of derivation of the signal. The gain adjustment comprises a photoresistor associated with a source of light which is provided with varying current corresponding to the signal to vary the resistance of the photoresistor and, thus, the gain value. The reset and rate adjustments may also comprise photoresistors with light sources or may be formed of field affect transistors each controlled by a circuit and remotely located potentiometer or variable voltage source.

Abstract: A buffer is described which includes two gain stages which may be constructed of MOS devices, the first stage having a low noise characteristic and the second stage having a high current drive capability. The second stage is switched in circuit only when high current drive is needed so that the buffer otherwise exhibits the low noise characteristics of the first stage. A feedback network is also switched in circuit in a manner that maintains the buffer's loop gain substantially constant, whether or not the high current drive stage is in circuit.

Abstract: An operational amplifier having an input stage, a voltage gain stage, a current gain or buffer stage and a feedback connected between the output of the buffer stage for supplying to the voltage gain stage a current which varies in proportion to the voltage gain stage output to increase the output impedance of the voltage gain stage.

Abstract: The disclosed invention is a programmable gain feedback amplifier consisting of a high gain (op-amp) amplifier, feedback elements and fuse networks in the feedback and/or input paths, a decoding circuit for receiving an input programming command signal, and thereby selectively blowing (or opening) the proper fuses to establish the desired signal attenuation in said networks. After programming, the gain of the amplifier circuit is related to the total attenuation of the network(s), is permanently set, and does not require the programming signal to be continuously applied. Embodiments are described which are compatible with monolithic microelectronic fabrication techniques.

Abstract: A nonintegrating, high sensitivity, wide dynamic range receiver is described. A voltage dependent current source is connected in negative feedback with a forward voltage amplifier. The transconductance of the current source is essentially independent of frequency within the signal bandwidth frequency, and the feedback pole is the dominant pole in the loop gain. To prevent saturation by high intensity input signals the receiver is combined with a range extender circuit.

Abstract: A high frequency amplifier circuit includes a series resonance circuit resonating at a desired frequency, first transistor to the gate of which are applied signals and to the source of which is connected the series resonance circuit, a second transistor to the base of which is applied the output signal from the first transistor, and third and fourth transistors having their emitters connected to the second transistor. The collector of the third transistor is connected to the source of the first transistor. A parallel resonance circuit resonates at the desired frequency. The collector of the fourth transistor is connected to the source of the first transistor via the parallel resonance circuit. An AGC circuit applies AGC voltage to the bases of the third and fourth transistors for the purpose of varying the collector current ratio of both the transistors. Negative feedback is accomplished in the circuit, and output power is obtained from the parallel resonance circuit.

Abstract: A tone control circuit including an amplifier having a continuously adjustable frequency response control for varying the effect of low and high frequency filters upon the amplifier, and incorporating a novel distortion and transient suppression circuit is disclosed. A programmable variable resistance is coupled between an input and an output of said amplifier to attenuate circuit low frequency response while initially varying resistor value in response to a programming distortion/transient control signal. Thereafter, overall amplifier gain is further varied in response to the programming distortion/transient control signal by further adjusting the variable resistor value. Various embodiments of the invention provide both continuous and discrete control of tone and volume responsive to both excessive low frequency signal and transients. The present invention is implemented in both discrete and monolithic embodiments, which include both linear and CMOS technologies.

Abstract: A voltage controlled capacitor is created by connecting a capacitance between the output of an amplifier whose gain is voltage controllable and an inverting input of the amplifier.

Abstract: In a circuit for amplifying and/or attenuating a signal, which circuit comprises an amplifier stage (3) having an inverting input and a non-inverting input and an output, a first voltage divider (5) having n taps (6.1, 6.2, . . . , 6.n) is arranged between an input terminal (1) and ultimately a point of constant potential (18). The taps (6.1, 6.2, . . . , 6.n) are connected to a first controllable switching unit (7) for switching individual ones of the taps (6.1 to 6.n) to the non-inverting input of the amplifier stage (3). Further, a second voltage divider (11) having m taps (12.1, 12.2, . . . , 12.m) is connected between an output terminal (2), which is the output of the amplifier stage (3), and (ultimately) the point of constant potential (18). The taps (12.1 to 12.m) are connected to a second controllable switching unit (13) for switching individual ones of the taps (12.1 to 12.m) to the inverting input of the amplifier stage (3).

Abstract: An integratable programmable attenuator includes in one embodiment a plurality of field-effect transistors coupled to a semiconductor resistor at spaced apart locations thereon, the semiconductor resistor forming one of the source/drain regions of each of the transistors. The other source/drain region of each field-effect transistor is selectively coupled to an input of a differential amplifier, the output of which is coupled to one end region of the semiconductor resistor. The gain of the differential amplifier is variable in predetermined steps according to which of the transistors is selected.

Abstract: An automatic level control circuit is constituted by a variable gain amplifier means supplied with an input signal, for outputting a level controlled signal; detector means for detecting the output signal of the variable gain amplifier means; integration circuit means including an operational amplifier and a capacitor; means for applying an output voltage of the detector means to a first input terminal of the operational amplifier via a first resistor; means for applying a first reference voltage to the first input terminal via a second resistor; a first diode with one end connected to the output terminal of the operational amplifier and the other end connected to one end of the capacitor; a second diode connected between the other end of the capacitor and the first input terminal; a transistor with its first and second electrodes connected in parallel with the capacitor and its third electrode connected to the output terminal of the operational amplifier; and circuit means which decreases the gain of the var

Abstract: A switching circuit for achieving the amplifying and muting operations is disclosed. The switching circuit operates as a non-inverting feedback amplifier whenever the circuit performs either amplification or muting. The non-inverting input port of the amplifier is always kept free to receive a given signal. An impedance element is connected to the output terminal of the circuit in either the amplifying or muting operation.

Abstract: A variable impedance circuit employing an RIS field effect transistor which greatly reduces distortion at low and high frequencies is obtained by providing means for applying voltages to the RIS field effect transistor at values determined by the following equations: ##EQU1## where V.sub.BG is the backgate voltage, V.sub.D is the voltage applied to the drain, V.sub.S is the voltage applied to the source, V.sub.BO is the DC component of the voltage applied to the substrate, K is a constant, .alpha..sub.1 is a constant, .alpha..sub.2 is a constant, V.sub.GS is the voltage applied to the gate at the end nearest the source, V.sub.GD is voltage applied to the gate at the end nearest the drain and V.sub.GO is a control voltage.

Abstract: Many signal processing applications of practical importance (for example, continuous-signal filtering) require high-precision temperature-insensitive transconductance elements. In accordance with one feature of this invention, a reference transconductance element is included in a control loop. The element consists of a MOSFET device or a MOSFET circuit in the loop. In the loop, the transconductance of the reference element is determined solely by the value and switching period of a switched-capacitor. The transconductance of the element is in effect thereby precisely matched against the conductance of the switched-capacitor.As the temperature of the chip varies, a control voltage is generated in the loop to maintain the transconductance of the reference element constant. This same control voltage is applied to other similar elements included in circuits (for example, filters) on the chip. In that way, the transconductances of these other elements are also matched to that of the switched-capacitor.

Abstract: Methods for operating a control circuit, having a programmable signal characteristic, in a manner so as to gradually vary a D.C. analog output level from an initial value to a final value, as well as for abrupt changes therein, when an isolation-and-rectification network is used to recover a D.C. voltage of programmably controlled amplitude. The methods also provide for a pulsed output condition in a circuit for providing a periodic signal of programmably controlled amplitude. In such a circuit, the output signal amplitude may be controlled by external data signals to values less than, equal to and greater than, the substantially constant amplitude of an oscillator waveform. Both programmable (computer-controlled) and hard-wired circuitry are disclosed for controlling the output signal by the methods of this invention.

Abstract: A signal gain controlled system comprises an operational amplifier including a feedback path between the input and output terminals of the amplifier. The system includes first variable impedance means for varying the output voltage at the output terminal of the amplifier in response to and as a function of the input current signal applied to the input terminal and a first control signal. A signal path coupled between the output terminal of the operational amplifier and the output terminal of the system includes second variable impedance means for varying the output current of the system in response to and as a function of (a) the output voltage at the output of the amplifier and (b) a second control signal. The signal gain of the system is a function of the ratio of the second and first control signals.The preferred amplifier is the type having an input resistance and a feedback resistance, wherein at least one of the resistances includes a transistor which is biased to operate in its saturated region.

Abstract: A compressor limiter is provided for the processing of audio signals. Fundamentally, the invention includes an amplifier receiving audio input signals and including a photoresistive element in the feedback circuit thereof. The output of the amplifier is provided to a dual stage control voltage generating circuit. The first stage generates a current through a light emitting diode corresponding to the amplitude of the output signal from the amplifier. The light emitting diode sets a threshold for suppression of the output audio signal such that, as light is emitted from the diode, it effects the photoresistor in the feedback circuit of the amplifier, thus adjusting the gain. The other branch of the control voltage generating circuitry comprises a peak detector which is operative for controlling the light emitted from the diode when successive audio signals exceeding the threshold are received in rapid succession.

Abstract: A treble-control circuit which exhibits a particularly low noise level and which can be controlled digitally in a simple manner. The treble control circuit comprises an amplifier having an output connected to the arrangement of a capacitor in series with a resistor chain. The tappings of said resistor chain are connected to an inverting input of the amplifier via a first switch and to the output of the treble control circuit via a second switch.

Abstract: An automatic signal level control device has a variable impedance element whose impedance varies with the level of a control signal; a variable gain circuit whose gain varies with the impedance of the variable impedance element; and a detector for generating the control signal upon receipt of an output signal from the variable gain circuit. The detector includes a transistor whose base is supplied with a first signal corresponding to the output signal from the variable gain circuit and from whose emitter there is drawn out a second signal having a potential corresponding to that of the first signal; a feedback element which is connected between the base and emitter of the transistor; and a capacitor which is connected between the emitter of the transistor and a circuit having substantially no AC potential to store a charge corresponding to the second signal.

Abstract: Amplifier gain is varied in response to a control voltage by a switched capacitor variable transconductance feedback network. First and second capacitors are connected in series between the input and the output of an operational amplifier. The input side of the first capacitor is switched by a first toggle switch between the input and ground. The output side of the second capacitor is switched by a second toggle switch between the output side and ground. Both toggle switches are operated by a pair of non-overlapping pulse trains. A voltage-controlled variable resistance network is connected between the common node of the capacitors and ground.

Abstract: A low-noise bass-control device, which is digitally controllable in a simple manner, comprises an amplifier having an output connected to the series arrangement of a capacitor and a tapped resistor chain. The taps on said resistor chain are connected to an inverting input of the amplifier via a first switch and to the output of the control device via a second switch.

Abstract: A high efficiency radio frequency amplifier is provided which includes stabilization circuitry which is selectively actuated during periods of time when undesired amplifier circuit operating conditions are present which tend to cause amplifier oscillation. Otherwise, the stabilization circuit remains in effect decoupled from the amplifier so as not to unnecessarily draw power from the amplifier circuit when its action is not required to prevent undesired oscillation of the amplifier.

Abstract: An amplification and sampling device for multiplexed analog signals comprises a continuous chain of amplification elements, means for giving to each of said elements a gain selected from a predetermined set of values, sample-and-hold units for memorizing the amplified voltages available at the output of said elements, means for correcting the drift or noise voltage of the amplification chain and selection means for applying to the amplification chain the samples of the multiplexed analog signals or the voltages memorized in the sample-and-hold units, in accordance with the voltage level obtained at the output of the amplification chain as compared with reference voltages.

Abstract: An adaptive equalizer for a twisted pair telephone line comprises a differential input/output amplifier, with the line connected to its positive input via a resistor and DC blocking capacitors. The junction of these capacitors is grounded via an adjustable impedance.The amplifier has a feedback loop with another adjustable impedance also connected to the negative input of the amplifier.Line impedance variations vary the impedance of both of the adjustable impedances, which, include diodes to separately compensate for the line's attenuation and frequency characteristics.

Abstract: An automatic level control circuit for an operational amplifier 16 for minimizing spikes or instantaneous gain of the amplifier at a low period wherein no signal is received on the input. The apparatus includes a multi-branch circuit which is connected between an output terminal 26 and a feedback terminal 34. A pair of zener diodes 50 and 52 are connected back-to-back in series with a capacitor 54 provided in one of the branches. A pair of voltage dividing resistors 44 and 46 are connected in another of the branches and a second capacitor 42 is provided in the remaining branch of controlling the high frequency oscillations of the operational amplifier.

Abstract: A wide dynamic range automatic gain ranging amplifier system includes an amplifier which receives an analog input signal and amplifies the received analog input signal in accordance with gain control signals to provide an amplified signal. A network connected to the amplifier also receives the analog input signal and provides the gain control signals corresponding to a desired gain for the amplifier in accordance with the received input signal and also provides gain status signals representative of the gain associated with the amplified signal.

Abstract: A variable gain amplifier includes an amplifier for amplifying an input signal, a switch controlled with a given duty factor and a smoothing filter connected to the switch. The filter and the switch constitutes a negative feedback loop for the amplifier of which amplification factor is variably controlled by varying the duty factor of the switch.