Abstract: An arrangement for suppressing audible noise occurring when audio equipment is switched on and off, in which a first electronic switch is connected to the output of an amplifier that has a negative feedback loop formed between the amplifier output and an inverting input of the amplifier. The output of the amplifier is connected to a load impedance through the first electronic switch. A second electronic switch is connected to a junction between the load impedance and the first electronic switch, and to the inverting input of the amplifier. A joint control line permits the two electronic switches to be turned on and off simultaneously. The two electronic switches can be connected in parallel through a feedback resistor in the negative feedback loop.

Abstract: An AGC system for controlling the gain of an amplifier includes an AGC multiplexer and an AGC circuit. The AGC circuit receives an input signal from the AGC multiplexer and generates, in response thereto a gain control signal. The AGC multiplexer operates in three modes. In a first mode, in which the erased portion of a sector is being detected, the AGC multiplexer couples an input preset signal of a predetermined voltage level to the AGC circuit, enabling it, in turn, to generate a gain control signal to control the gain to a predetermined level. In a second mode, the AGC multiplexer couples a signal related to the output signal from the amplifier to the AGC circuit, enabling the AGC circuit to generate a gain signal related to the output level of the amplifier. In the third mode, the AGC multiplexer maintains its output signal constant, thus enabling the AGC circuit to maintain its gain control constant.

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: 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: 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 circuit useful as a voltage tunable resistive element comprises four matched MOS transistors in which each of the first and second have their drains interconnected to a first input terminal and each of the third and fourth have their drains interconnected to a second input terminal, the first and third have their sources interconnected to a first output terminal and the second and fourth have their sources interconnected to a second output terminal, and the first and fourth have their gates interconnected to a first control terminal and the second and third have their gates interconnected to a second control terminal. A continuous-time integrator is described which includes such a resistive element.

Abstract: A method and apparatus are disclosed for regulating the operation of a TWT. The TWT regulation is achieved by detecting the operating condition of the TWT, e.g., by measuring dynamic gain, and regulating feedback of the TWT output in response to the TWT operating condition. The invention is preferably implemented so as to augment the TWT input drive from an exciter source to induce the TWT to drive itself into saturation. The inventive technique comprises determining whether the TWT is operating in a desired operating condition, e.g., saturation, feeding back to the TWT input a portion of the TWT output power to the TWT input, and regulating the feedback signal to keep the TWT operating in the desired condition. Determination of whether the TWT is operating in a saturation condition may be affected through measurement of the TWT dynamic gain. The invention permits dynamic management of the feedback to accommodate variations in gain of the TWT, e.g.

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: Herein disclosed is a variable gain amplifying circuit which comprises a heating element, a heat-sensitive resistance coupled thermally to the heating element, an amplifier including the heat-sensitive resistance, and means for controlling the heat of the heat element. This heat of the heating element is controlled so as to control the value of the heat-sensitive resistance. As a result that the value of the heat-sensitive resistance is controlled, the gain of that amplifier is controlled.

Abstract: A railway vehicle brake control system in which a fluid pressure brake continuously supplements the electric brake as the electric brake effectiveness fades during vehicle slowdown. An amplifier circuit output signal corresponding to the electric brake effectiveness is modified by adjusting the amplifier gain in response to a detector sensing the initial drop in the electric brake effectiveness. This modified amplifer output signal is subtracted from a brake command signal to obtain a difference signal, the value of which establishes the amount of fluid pressure braking necessary to supplement the electric brake deficiency. The arrangement compensates for hysteresis and response delay in the pneumatic valving required in the fluid pressure brake system, such that the total brake obtained corresponds substantially to the brake command both during and following transition from the electric brake to the fluid pressure brake.

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 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: An improvement to a linear power amplifying system is disclosed which maintains the DC balance of the envelope feedback loop under adverse conditions, thereby improving the accuracy of the system. The improvement is realized through the addition of two differential amplifier stages to the feedback loop. A first differential amplifier 103 is added to the balanced outputs of the synchronous envelope detector 102, which is comprised of an active balanced modulator/demodulator device, to correct for the common-mode DC drift of the detector. An auxiliary feedback loop, comprised of a second differential amplifier 104 and a low-pass filter, compares the average DC value of the envelope error signal to a system reference voltage V.sub.R, and produces a loop gain error signal which corrects for variations in envelope feedback loop gain. The improvement provides envelope modulation transmitters with a substantial reduction in adjacent-channel interference and lower on-channel distortion.

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 digital control amplifier is provided as a unitary monolithic device to control the transfer function of an analog signal in response to a digital control, such as from a digital computer. A current transfer cell is employed which uses an amplifier circuit having transistors of like polarity, and is capable of both attenuation and greater than unity amplification of an input analog signal. A digital-two-analog converter is integrated into the system and employs a series of current dividers which enables a common reference current to be used for each bit of the converter. A current reference circuit for the converter employs a band gap voltage regulator with a temperature compensation design that varies the control signal applied to the current transfer cell to compensate for temperature-induced variations in the output of the cell.

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: An electronic amplifier having a transmission factor which can be varied by means of a control voltage, specifically an expander. A switch is provided for selective operation of the amplifier with a fixed control voltage or with a variable control voltage, with this switch being coupled with circuitry for reducing, during operation of the amplifier with a fixed control voltage, the output voltage of the control circuit generating the variable control voltage.

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: 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 electronic impedance circuit is constructed of a voltage-current converter whose input terminal is supplied with an input signal voltage, and a variable-gain current amplifier whose input terminal is supplied with an output current of the voltage-current converter and whose output signal current is fed back to the input terminal of the voltage-current converter.In order to prevent the undesirable oscillation phenomenon of the variable electronic impedance circuit immediately after the closure of a power supply, a control circuit which operates for a predetermined time after the closure of the power supply is especially arranged.Since an output signal from the control circuit inhibits the operation of the variable-gain current amplifier during the predetermined time, the unstable operation immediately after the closure of the power supply can be prevented.

Abstract: An amplifier circuit comprising an amplifier (1) having an input (11) which receives an electric signal comprising an intermittent useful signal component V.sub.U and an undesired spurious component V.sub.D and an input (12) of opposite sign to that of the input (11). The output signal of a circuit (2) for the compensation of the spurious component is applied to amplifier input. The circuit (2) comprises a comparator (20) for comparing the undesired component, taken from the output of the amplifier (1), with a threshold value, a counter (21) which is incremented or decremented depending on the result of the comparisons and in the rhythm of a clock circuit (22), and a digital-to-analog converter (23) coupled to the output of the counter (21) to supply the signal for the compensation of the unwanted component to the input (12).

Abstract: An electrical signal converter with step variable gain comprises a variable gain circuit having its control inputs connected to the outputs of a sequencer for varying the gain of the variable gain circuit according to a step function of time. A negative feedback path between the output and the input of the variable gain circuit includes a second variable gain circuit, whose control inputs are connected to the outputs of the sequencer for varying the gain of the second variable gain circuit in inverse proportion to the abovementioned step function of time.

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 ladder network includes a plurality of cascaded prototype network sections connection in cascade and terminated with a termination resistor. The sections each provide gains of 1/2, 2/5, 1/5 and 1/10. Linear circuits are also disclosed which utilize at least one amplifier and the ladder network in a feedback loop.

Abstract: A voltage controlled current source provides a load current through a load impedance which is a function of an input voltage and is independent of the impedance value of the load impedance. The voltage controlled current source includes a high input impedance unity gain instrumentation amplifier and a resistor connected in series with the load impedance so that current flows through the resistor and the load impedance. The instrumentation amplifier receives the input voltage at its inverting input and receives a load voltage representing the voltage across the load impedance produced by the load current at its noninverting input. The instrumentation amplifier subtracts the input voltage at the inverting input from the load voltage at the noninverting input and multiplies by a gain of one to produce an output voltage at its output. The resistor and the load impedance are connected in series between the output of the amplifier and a reference voltage (e.g.

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: 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: In a circuit for the automatic dynamic compression or expansion of a signal, the circuit presenting a useful signal path containing a first variable gain member which is electronically controllable for varying the transmission factor between the circuit input and output, a branch path connected at one point to the useful signal path and containing a control voltage generator for generating a control voltage from the signal at such point in the useful signal path, and a second variable gain member which is connected in the branch path and which is electronically controllable for varying the transmission factor exhibited by the branch path, with the transmission factor of the useful signal path being controlled to have a value dependent on the value of the control voltage and a counterregulation of the transmission factor of the branch path being effected relative to the transmission factor variation imparted to the useful signal path, the useful signal path includes a device causing the signal at one point alo

Abstract: An AC resistor attenuator with low parasitic capacitance coupling and, thus, a substantially constant attenuation value over a relatively wide frequency range is disclosed. The AC resistor attenuator comprises a first elongate resistor substantially entirely surrounded by a second elongate resistor. The first and second elongate resistors are thermally matched and have a substantially identical resistance profile. The first and second resistors are connected in series. The other ends of the first and second resistors are connected across the source of the signal to be attenuated. The attenuated signal is obtained at the junction between the first and second resistors. Except in the case where fifty percent (50%) attenuation is to be provided, the higher value resistance of the attenuator forms the first resistor and the lower value forms the second resistor.

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: In a signal expander, the envelope of an input signal to be expanded is detected and applied as a control signal to the gain control input of a variable gain device which expands the input signal. The control signal is applied to the variable gain device via an adaptive filter having improved ripple reduction and transient performance characteristics to minimize audibility of gain changes. The adaptive filter includes a low pass filter for producing a smoothed control signal essentially free of ripple and an analog gate for coupling the greater of the smoothed signal or a further signal to the variable gain device, the further signal being equal to the detector output signal less a constant. Compression of an input signal is provided by applying the input signal to the non-inverting input terminal of an amplifier and coupling the (compressed) output signal of the amplifier to its inverting input terminal via the expander.

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.

Abstract: An automatically adjusted equalizer circuit includes an operational amplifier having a parallel resonant circuit, a voltage controlled resistor, and an amplifier output signal monitoring circuit in a feedback path for the adjustable equalizer. The presence of the parallel resonant circuit in the feedback path causes the amplifier gain to vary with frequency. An input signal to the operational amplifier will be distorted depending upon the particular loss characteristic of a telephone wire to which the input is connected. Automatic adjustment of the voltage controlled resistor, and the presence of the resonant circuit, causes the slope of the gain of the amplifier to inversely compensate for the loss characteristic of the particular line in question. Within the variety of lines, each line will have different loss characteristics as a function of length and gauge of the different telephone lines.

Abstract: The device is adapted to sample and amplify with an optimum gain multiplexed analog signals. It comprises a chain of three interconnected amplifiers, the first of which has a gain of unity, the respective gains of the two others being selected in dependence on their output voltage as compared to a reference voltage. It also comprises three memorizing capacitors each of which is adapted to memorize the output voltage of a corresponding amplifier, and switches, actuated in accordance with the gain selection for each amplifier, to make the necessary connections for operating the chain of amplifiers with the selected gain.

Abstract: A feedback amplifier is configured as a contrast compressor for video signals including a reference blanking level. A feedback resistance is divided into two resistors coupled at a juncture. Contrast compression is accomplished by a diode coupled to the juncture and to a voltage source which may be adjusted to vary the point of onset of compression. The diode current perturbs the operating point of the amplifier, thereby producing a condition in which the blanking level at the output is other than zero volts. This is undesirable as it may affect following circuits adversely or require further setup. A clamp is coupled to the inverting input terminal for offsetting the perturbation of the amplifier operating point caused by the diode current.

Abstract: A prescription attenuator comprising a plurality of cascaded L-pad sections coupled together to form an attenuator network wherein each cascaded section includes a single pole switch for activating its respective section. The network impedance values are selected so that single L-pad section activations produce actual attenuations slightly more than an ideal level of attenuation wherein multiple section activations tend to keep the error evenly distributed about the ideal level of attenuation.

Abstract: In a two-band compander pre-emphasis is carried out during compression and de-emphasis during expansion in the lower frequency range. Noise suppression is improved by this measure.

Abstract: A feedback signal amplifier circuit having switchable closed loop gain in sponse to the output signal level of the amplifier for limiting the output signal level is presented. The feedback ratio of the circuit is switched by output signal level responsive diodes which derive signal level determining bias from both an unregulated power supply and the output terminal of the amplifier. A bias compensation network deriving bias from the unregulated power supply is connected to a bias sensitive input of the amplifier for tracking changes in power supply voltage which are reflected into the output of the amplifier for keeping the signal level determining bias of the diodes essentially constant and independent of changes of power supply voltage.

Abstract: A signal control apparatus controls the gain of an amplifier in a proportional stepwise manner to produce in response to an input signal an output signal having a magnitude of relatively accurately controlled value. The amplifier gain is controlled in steps that are proportional to a parameter, such as the magnitude of the output signal itself, thereby providing an automatic gain control function. A method also is disclosed for effecting such signal control. Moreover, such apparatus and method are employed in a system and method for monitoring the occurrence of plural events in a cyclical process, such as the travel of a conveyor belt, the system, then, preferably being a conveyor belt rip detector system.

Abstract: A circuit for varying the gain of an amplifier circuit linearly in decibel by the use of a digital code signal varying linearly, wherein a resistance network to be connected between an amplifier having a fixed gain and an input or output portion for the amplification is connected and the gain of the amplifier as well as the values of resistance elements constituting the resistance network is set so that the transfer function of the amplifier circuit may become: ##EQU1## .

Abstract: A compander system wherein, for compatibility with systems of constant amplification, dynamic compression and expansion are effected only within a limited level range.

Abstract: A multiband compressor suitable for compressing the dynamic range of an audio signal in a broadcasting system is disclosed. The frequency band with the highest predictable energy is selected as a master band with the energy level in this band used to control the gain in the other (slave) bands. When the energy in a slave band exceeds a predetermined level, additional control of the signal level in that band occurs. The described compressor has the advantages of both the wideband compressors and multiband compressors without the disadvantages of these compressors. In addition to the compressor, a unique overshoot protection circuit is described.

Abstract: A noise reduction system having an encoder which compresses the dynamic range of an analog audio signal, a transmission medium coupled to the encoder, and a decoder coupled to the transmission medium for expanding and thereby restoring the dynamic range of the compressed analog audio signal. The encoder includes a voltage controlled amplifier (VCA) receiving the audio signal, a high-pass filter also coupled to the analog audio signal, a circuit for obtaining a difference between the outputs of the VCA and the high-pass filter, weighting and level sensing circuits coupled to the encoder output for sensing the level of the compressed analog audio signal, and a limiter circuit coupled to the output of the weighting and level sensing circuits and producing a control voltage applied to the VCA control input in such a manner that the ratio of the gain of the VCA and the gain of the high-pass filter at the pass band thereof does not become less than one.

Abstract: A circuit arrangement for automatic dynamic compression and/or expansion having an auxiliary circuit provided in the useful signal path or in the negative feedback path of an amplifier. The auxiliary circuit has a first and a second connection point. On the one hand there are arranged between the first and the second connection point a first damping or amplifying member, an electronically controllable damping member and a second damping or amplifying member connected in series. On the other hand means for limiting the voltage or current are arranged between the first and second connection point.