Abstract: A system is disclosed for positioning an instrumentality over a predetermined range in response to a digitally coded position signal. To effect a controlled reduction in the instrumentality movement, an operational amplifier is provided having a feedback circuit including a fixed resistor and a controllable switch connected across the resistor. The switch is selectively controlled to short circuit the resistor at a controlled rate to effect a controlled gain reduction for the operational amplifier.

Abstract: A variable gain alternating voltage amplifier having a d.c. negative feedback loop for setting the operating point of the amplifier wherein a change in gain of the amplifier is effected by a variable resistance feedback loop which is connected in parallel with the d.c. negative feedback loop and includes the series connection of a controllable resistor and a capacitor.

Abstract: A programmable amplifier includes an operational amplifier receiving an analog input signal of a given polarity and voltage range and a read only memory (ROM) control which actuates six switches in a resistor configuration connected to the amplifier in such a manner as to provide a selection of two gain factors and direct or inverted polarity output in response to combinations of digital signals on two input lines to the ROM.

Abstract: A wide dynamic range automatic high speed gain ranging amplifier system includes a receiver circuit adapted to receive an analog input signal. A single stage amplifier is connected to the receiver circuit which amplifies a received analog signal to provide an output signal. A control circuit connected to the receiver circuit and to the amplifier controls the gain of the amplifier in accordance with the output signal and provides digital gain signals corresponding thereto.

Abstract: Disclosed is an analog tuning circuit, suitable for multiplexing, having a field-effect transistor connected to the output of an operational amplifier with the drain connected in a feedback loop to the inverting input of the amplifier.

Abstract: A circuit for optional dynamic compression or expansion, with one amplifier located in the useful signal path and controllable in amplification, and an auxiliary branch including one amplifier controllable in amplification and a control voltage generator, to the input of which a useful signal path is connected and the output voltage of which serves to control the controllable amplification in the useful signal path and in the auxiliary branch, and wherein as adjusting members for controlling the amplification of the controllable amplifiers there serve field effect transistors to the control electrodes of which respective direct control voltages are applied. In parallel with the source-sink path of one field effect transistor serving as adjusting member for an amplifier located in the useful signal path there is connected a voltage divider the tapping of which is connected via a separating amplifier to the control electrode of the field effect transistor.

Abstract: Left and right stereo power amplifiers receive power from the 12-volt D.C. automobile supply bypassed by a single capacitor for both amplifiers and energize left and right loudspeakers in series with the junction of the series-connected speakers coupled to ground through a capacitor that allows the left and right speakers to be independently driven by the left and right power amplifiers, respectively, by spectral components above the crossover frequency determined by the speaker impedance and the capacitor impedance. Each power amplifier is driven by an equalizing circuit including a photocell illuminated by an LED that is driven by a feedback signal from the power amplifier.

Abstract: A high fidelity hearing aid is disclosed for providing high quality sound and is primarily directed to those users whose hearing loss is such that they need some amplification for low level signals, but do not need amplification for high level signals.

Abstract: The present invention concerns the transmission of information, and consists in a continuous regulator responsive to the amplitude of a pilot tone included in the signal whose level is to be regulated, including a variable-gain quadripole through which said signal is passed, an automatic gain control loop including a circuit controlling the gain of the quadripole, and an auxiliary feedback loop through which the control circuit also controls the automatic gain control loop. The regulator is applicable with advantage to transmission systems.

Abstract: A digital gain control system is disclosed. A clock oscillator drives a counter which in turn provides an output to a D/A converter. The analog output of the converter is used to develop a signal for controlling the gain of a gain-controlled amplifier. In order to compensate for the nonlinear gain versus control current characteristic of the amplifier, additional circuitry is employed so that the initial increment in control current, that is, the increment that occurs as the counter goes from the 0000 to the 0001 state, is significantly greater than the remaining increments. In conjunction with volume control circuitry for audio amplifiers, this circuitry assures a muted condition in the 0000 state, and an audio output corresponding to at least the minimum discernible level in the 0001 state.

Abstract: A variable resistance device utilizes a control signal variable resistor and a first fixed resistor connected in series as a voltage divider as well as a second fixed resistor and an operational amplifier having an input connected between the first fixed resistor and one side of the variable resistor and an output connected through the second fixed resistor to the other side of the variable resistor, as a substantially linear variable resistance device where the variable resistance is obtained across the voltage divider.

Abstract: The gain of an operational amplifier is switched between +K dB and -K dB by switching circuit positions of the input and feedback impedances. The gain is changed in 0.1 dB steps by changing either the input or feedback impedance by a ratio of 1.0116 for each step. The gain is changed in 1.0 dB steps by changing the other of the feedback or input impedance by a ratio of 1.122 for each step. A novel two-pole switching arrangement employs the foregoing techniques to permit unambiguous gain polarity changes.

Abstract: The circuit includes a signal path extending between an information signal input terminal and an information signal output terminal. A differential amplifier, having a non-inverting input and an inverting input, is included in the signal path, and a feedback path, containing electronically controlled impedance, connects the amplifier inverting input to the amplifier output. A branch path is branched off from the information signal output terminal and, in this branch path, a control voltage is derived from the information signal and fed to the electronically controllable impedance. In accordance with the invention, the information signal input terminal is connected to the non-inverting amplifier input to feed the information signal thereto. Two diodes are connected in parallel with each other, but in oppositely poled relation, across the feedback circuit, to limit the feedback voltage between the amplifier output and the amplifier inverting input.

Abstract: Compandor apparatus including a compressor comprised of an operational amplifier having a plurality of gain controlling feedback paths that are respectively responsive to different portions of the input frequency spectrum, and an expandor comprised of an operational amplifier having a plurality of gain controlling circuits that are respectively responsive to different portions of the input frequency spectrum.

Abstract: A switchable gain amplifier for use in an FM broadcasting system wherein the gain of a modulating signal is automatically switched to a selected level in accordance with the use or non-use of plural input channels.

Abstract: A circuit for adjusting the amplitude of a reference signal to a predetermined level so as to permit subsequent data signals to be interpreted correctly. The circuit includes an operational amplifier having a feedback circuit connected between an output terminal and an input terminal; a bank of relays operably connected to a plurality of resistors; and a comparator comparing an output voltage of the amplifier with a reference voltage and generating a compared signal responsive thereto. Means is provided for selectively energizing the relays according to the compared signal from the comparator until the output signal from the amplifier equals to the reference signal. A second comparator is provided for comparing the output of the amplifier with a second voltage source so as to illuminate a lamp when the output signal from the amplifier exceeds the second voltage.

Abstract: The automatic range selection circuit is particularly useful with a photomultiplier tube linear microphotometer and includes an amplifier, adjustable and switchable impedances coupled between an input and an output of the amplifier for adjusting the gain thereof, two comparators for comparing the output from the amplifier with upper and lower reference voltage levels, an integrator for integrating the output of the comparators, and an analog control circuit responsive to the output signal level at the output of the integrator for controlling the amount of impedance coupled between the input and output of the amplifier thereby to automatically adjust the gain thereof.

Abstract: A variable sensitivity monitor circuit changes sensitivity for a period immediately following startup or turnon of the process or equipment being monitored. By changing sensitivity, the monitor circuit will not respond to the transient produced at startup or turnon but will respond to any abnormal condition greater than the transient without any decrease in response time of the monitor circuit.

Abstract: A sensitivity control circuit is described for use with a sound movie camera having an automatic sound level control circuit. In one embodiment, the automatic sound level control circuit includes a pair of cascaded amplifiers whose overall gain is controlled by the conduction of an active control element. The active control element has an input terminal which receives a control signal representative of the amplitude of the signal output of the cascaded amplifiers. To desensitize the automatic sound level control circuit to background noise, a voltage source and a variable impedance element are serially coupled to the control terminal of the active control element to provide a control current for selectably varying the conduction of the active control element. The gain of the cascaded amplifiers is thereby selectively controlled and the sensitivity of the automatic sound level control circuit is reduced.

Abstract: An amplifier whose transmission factor is to be controlled as a function of a control voltage and including an amplifier member having a negating input, connected to have its impedance varied by the control voltage and an electronically controllable variable impedance having one side connected to the amplifier member output, a second impedance connected between the other side of the first impedance and ground, and a switch assembly for switching the connections within the amplifier between two operating states providing mutually complementary control characteristics, the amplifier member output providing the amplifier output in one operating state and being connected to the negating input in the other operating state, and the point of connection between the impedances being connected to the negating input in the one operating state and providing the amplifier output in the other operating state.

Abstract: A transconductance amplifier circuit including two operational amplifiers, as shown in the accompanying drawing, is disclosed. The gain of the amplifier circuit is determined by the resistances R1, R2, R3 and R4. The scale factor relating the output current i.sub.out to the input voltage e.sub.in is determined by the setting of the switches S1, S2, and S3, which adjust the amount of resistance between the output current terminal I.sub.o and the output terminal of the second operational amplifier A2. For R1/R2 = 1; R3/R4 = 1; and switch S1 closed i.sub.out = e.sub.in /R5. This transconductance amplifier circuit provides common mode rejection between the input voltage and the output current.

Abstract: A multistage amplifier having an automatically programmable gain is disclosed in which the amplifier gain is incremented in binary steps to a desired level. Each amplifier stage is switchable between a first and second gain in a binary sequence such that the four digit output of a sixteen bit counter will increment the total amplifier gain in sixteen binary steps.A readback and decoding circuit for reading magnetic tape is also disclosed in which the signal amplitude of data read from the magnetic tape is compared to a reference voltage which corresponds to the data readback clipping level. Only amplified data which exceeds the predetermined clipping level is gated out of the circuit for processing.

Abstract: A gain control circuit includes an audio signal attenuator circuit and a circuit for controlling the current in the audio signal attenuator circuit. The audio signal attenuator circuit is inserted between an input terminal of an amplifier circuit for amplifying an audio signal and an output terminal of a diode for detecting and rectifying part of the audio signal appearing at the output terminal of the amplifier circuit. The signal attenuator circuit and the current control circuit comprise a plurality of transistors and operate when, in response to application of an audio signal to the amplifier circuit, a DC voltage of certain level is produced at the output terminal of the rectifying diode. Part of the audio signal applied to the amplifier circuit is bypassed and attenuated, while at the same time stabilizing the DC bias in the amplifier circuit.

Abstract: A voltage controlled variable gain circuit comprising: first, second, third and fourth same polarity transistors for dividing the output current of a first operational amplifier by dc gain control voltage and being connected with the output terminal of the first operational amplifier to which an input signal is applied; means for driving in inverse phase the respective pairs of a first and third transistors, and a second and fourth transistors; a first feedback circuit including a second operational amplifier with an inverting input terminal connected with the output terminal of the first transistor, a first resistor element and a first PN junction element connected in series between the input and output terminals of the second operational amplifier, and a second resistor element and a second PN junction element connected in series between the output of the second operational amplifier and the input terminal of the first operational amplifier, so as to negatively feedback the output current of the first trans

Abstract: A digitally controllable amplifier unit and musical instrument amplifier incorporating such a unit. Digital control of the transfer function of a high-gain virtual-earth amplifier is effected by switching input and feedback impedances by means of transistor switches. Digital storage means are used to control the transistor switches.

Abstract: An acoustical testing system is described wherein a stabilized and calibrated audio sound generator is used to drive a device to be tested with the output of the device being processed by circuit means that are automatically self-adjusting thereby resulting in digital readouts of the device's output amplitude and purity.

Abstract: An amplifier circuit including a differential amplifier and having an effective transmission frequency band delimited by a lower limit frequency which can be varied by application of a control voltage is also given a defined upper limit frequency by connecting a resistance in series with a frequency dependent impedance between an inverting input of the amplifier and a point at the circuit reference potential. The value of the resistance can be adjusted to provide the desired upper limit frequency value and can be varied to change that frequency value.

Abstract: An improved gain control circuit for an amplifier having a plurality of parallel connected resistors each having a series switch to selectively switch the resistor into the control circuit to vary the gain incrementally as some continuous function of amplifier input voltage. In one embodiment, the parallel resistors are connected between the amplifier input and output. Alternatively, the parallel resistors may be connected as the amplifier input resistance. A peak follower circuit monitors the amplifier input and applies an output control voltage to a plurality of comparators each having a separate reference voltage. Each comparator generates an output signal when the control voltage exceeds its associated reference and this output is connected to one of the resistor switches to change the parallel resistance incrementally generating a corresponding incremental gain variation.

Abstract: An improvement is disclosed for use in a chromatographic system of the type including detector means providing a detector output signal indicative of the level of a component sought to be determined, detector output amplifier means for receiving the signal, an error signal balancing loop connected to the amplifier output to provide a balancing signal in feedback relationship to the amplifier, and means for adjusting the sensitivity range of the amplifier.

Abstract: An amplifier circuit having a variable transmission factor and an effective transmission frequency band delimited by a lower limit frequency is arranged to enable the value of the lower limit frequency to be varied as a function of a control voltage, by including in the circuit an amplifier member and circuit components defining a feedback path connected between the output of the amplifier and an input thereof which is inverting with respect to the output signals of the amplifier, the components defining the feedback path including an electronically voltage-controllable resistor having a control voltage input and a first frequency dependent impedance connected in parallel with the resistor, and the circuit further including a second frequency dependent impedance connected between the inverting input of the amplifier and a point at the circuit reference potential, and a line for supplying the control voltage to the control voltage input of the controllable resistor.

Abstract: A circuit for storing a DC voltage which may be used to control the volume, brightness, contrast, tint or color characteristics of a television receiver includes a semiconductor switching circuit for selectively coupling a DC voltage to a voltage storage capacitor through a DC impedance path. The DC impedance path is coupled between the inverting and noninverting inputs of an operational amplifier. The output of the operational amplifier is coupled to a utilization circuit to be controlled. A feedback path is coupled between the operational amplifier's output and inverting input to provide negative feedback so that a voltage balance is maintained between the inverting and noninverting inputs and thereby substantially eliminate leakage current flow to or from the storage capacitor through the DC impedance path.

Abstract: An electrical circuit for suppressing the effect of interfering alternating oltages of various frequencies superimposed upon a direct current signal in an electric measurand transmitter, such as in an electromechanical precision or fine balance, which comprises a signal line for carrying said direct current signal and interfering alternating voltages, means for low energy capacitively coupling-out of interfering alternating voltages of frequencies lower than a predetermined limit frequency from the signal line, means for energy amplifying and for inverting 180.degree. in phase said coupled-out voltages, and means for capacitively coupling-back into the signal line the amplified and inverted coupled-out voltages.

Abstract: Signal expansion/compression apparatus wherein an input signal is compressed by an exponential factor and then subsequently may be expanded by the reciprocal of that exponential factor, wherein neither the signal compression circuits nor the signal expansion circuits need be provided with exponential amplifiers or logarithmic function generators. The signal compressio circuit includes a plurality of serially-connected voltage controlled amplifiers, a first of such amplifiers receiving the input signal to be compressed and a predetermined one of such amplifiers providing the compressed output signal. A control signal generator is connected to the last of the voltage controlled amplifiers to produce a control voltage which is a function of the output signal of that last amplifier and a reference voltage. This control voltage is supplied to all of the voltage controlled amplifiers so as to determine the respective gains thereof.

Abstract: A communications receiver transversal filter equalizer is disclosed of the type using fixed increment tap weight adjustments involving use of amplitude data from the incoming signal in conjunction with tap weight adjustments.

Abstract: A decoded PAM input signal is coupled through a first polarity switch (which for one polarity of a polarity signal is closed) to the positive input line of a differential operational amplifier and through the series combination of a second polarity switch (which is open for the one polarity) and an input resistor to the negative input line of the differential amplifier. The positive input line is resistively connected to ground through a first bias resistor and is also connected to ground through the series combination of a second bias resistor and a third polarity switch which is also open for the one polarity. A feedback resistor is connected between the output line and the negative input line of the amplifier.

Abstract: Gain control circuits in the base and emitter circuits of a common-emitter transistor amplifier stage each include pluralities of resistors and electrically conductive screw-type switches which are connected together such that the net changes in decibel values of gain provided by closing individual switches are cumulative. Resistors in the emitter gain control circuit are electrically connected in parallel with the emitter resistor in the AC equivalent of the amplifier in various configurations by closing screw switches to decrease the effective emitter resistance and thereby increase the decibel value of amplifier gain in steps of prescribed magnitudes. The switches are selectively closed in a prescribed manner to provide step changes in the decibel value of the net gain of the stage in discrete consecutive steps of the same magnitude. Transistor amplifiers with emitter gain control circuits may be connected in series to provide additional steps and range of voltage gain.

Abstract: The output of an amplification assembly is coupled with the input of an integrating circuit by means of a first controlled switch. The output of the integrating circuit is coupled with the input of an intermediate stage and subtracted from the amplifier input signal during quiescence of the amplifier. The signal delivered by the amplification assembly is also applied to the input of a logical detection circuit which opens the first switch and closes a second switch discharging the integrating circuit in response to any rapid-variation pulse applied to its input, thus disabling the integration-subtraction operation, but closes the first switch and opens the second to enable integration and subtraction when the signal applied to the input of the detection circuit is steady or is subject only to slow variations.

Abstract: In a bridge circuit consisting of diodes connected in each circuit branch in a forward direction from one of a pair of opposing terminals to another with a current flowing through these diodes, impedance between a second opposing pair of terminals varies in correspondence to the magnitude of the constant current. The invention utilizes this phenomenon and provides a voltage-controlled filter employing this bridge circuit as an impedance element for determining its frequency region and thereby being capable of controlling its frequency region by voltage controlling. A primary passive low-pass filter is described as a preferred example of the invention. The invention further provides a voltage-controlled filter having the bridge circuit provided in a negative feedback loop of an amplifier in an active filter circuit and thereby being capable of controlling selectivity Q by controlling the gain of the amplifier by voltage controlling.

Abstract: An amplifier circuit whose gain bears a desired relation to a control voltage, including a differential amplifier, a plurality of impedances interconnected between the amplifier terminals and switches interconnected with the impedances and switchable between two states which create two impedance configurations that give the circuit mutually complementary gain vs. control voltage control characteristics.

Abstract: A gas analyzer has an output amplifier circuit which is drift compensated in that zero volts are established across a gain network for a particular low point measuring signal as the amplifier provides an output on the basis of a particular bias, while the gain network is adjusted so that the amplifier output equals a second reference signal. The drift compensation is automated in that the bias and the reference are used to drive adjusting devices while the gas analyzer receives particular reference gases.

Abstract: The compression portion of an instantaneous companding (compressing-expanding) system includes at least two and preferably four "bi-gain" amplifiers connected in cascade. Each bi-gain amplifier normally has a low-gain state and can be switched to a discrete high-gain state. A discrete reference voltage is provided to compare with the output of each amplifier. The amplifiers are initially switched to their low-gain states and the reference voltage corresponding to the first amplifier is selected. A comparator means makes a comparison between the system's output voltage and the selected reference voltage. The control means switches the first amplifier to its high-gain state or holds it in the low-gain state depending on the result of the comparison. By utilizing a different variable reference voltage and bi-gain amplifiers with two different amplification factors, the number of amplifiers and comparisons is significantly reduced.

Abstract: The analog signals provided by a seismic-velocity well logger, resulting from the transmission of seismic impulses from a transmitter to a receiver in a logging sonde in a well by paths that include travel through the rock walls of the borehole, are digitally recorded. These seismic impulses and the resulting received seismic signals, or traces, are repeated approximately 20 times per second. The recording apparatus digitizes these analog traces by determining signal amplitudes at intervals of approximately 10 microseconds and temporarily stores the digital values. The apparatus includes a programmable-gain amplifier, an analog-to-digital converter, a computer, and a memory in which are, in addition to the data, also stored the values of gain which are to be used in digitizing the next signal. That is, on each digitizing interval a stored gain "program" is read out of the computer and sets the gain of the amplifier.

Abstract: A voltage controlled filter with a plurality of cascaded phase shift circuit stages in a negative feedback path of an amplifier. Each phase shift circuit stage is a RC phase shift network which includes a series capacitor and a field effect transistor (FET) with its source-drain circuit connected as a shunt to ground. The magnitude of the effective source-drain resistance of the FET in each stage is controlled by a DC control voltage which is applied in common to the gate of each FET.

Abstract: A broad band amplifier with negative feedback and controllable amplification factor for use in a carrier frequency system is described. The amplifier is preferably used as a control amplifier in the receiver of a basic group, for example, a basic 60-group of the system wherein the amplification of the amplifier is then controlled by a pilot receiver common for all the 60-groups. The amplifier includes an amplifier stage having constant amplification and which receives the pilot signal. A negative feedback path is connected via a first impedance converter from the output to the input of the amplifier stage. This path includes a capacitive voltage divider together with a second impedance converter and an RC-link. The capacitor values in the voltage divider are varied in dependence on a regulating voltage from the pilot receiver of the system, whereby the degree of negative feedback and thus the amplification of the amplifier can be controlled.

Abstract: A variable resistance circuit comprising a field effect transistor, a plurality of amplifiers and a feedback circuit for one of the amplifiers with the equivalent resistance value derived from a circuit comprising the field effect transistor electrodes and a reference resistor being controlled by a digital signal or a pulse-width signal supplied to the feedback circuit.

Abstract: Apparatus for electrically communicating between a given location and a variably spaced apart remote location, the locations being connected via electrical conductors. A variable gain amplifier is connected in series between the spaced apart locations for variably amplifying the signals communicated therebetween. A gain control signal that is a function of the separation between the locations is generated and applied to the variable gain amplifier to vary the gain of the amplifier in accordance with the distance between the locations. The gain control signal is proportional to the effective resistance of the electrical conductors extending between the locations. The gain of the amplifier is varied by varying the transconductance of a transconductance amplifier connected in the amplifier feedback circuit in accordance with the gain control signal.

Abstract: One junction field effect transistor is connected in shunt with an operational amplifier so as to render its gain zero when no voltage is applied to its gate and another junction field effect transistor is connected so as to shunt the output of the amplifier to ground when no voltage is applied to its gate.

Abstract: A recirculatory analog signal sample amplifier having at least a first prtermined gain is provided with error determining means for recirculating a zero input signal with a second predetermined gain, thereby obtaining an error signal, and correction means to deduct from an incoming sample, before its circulation, a value proportional to the error signal.

Abstract: A signal frequency band control system comprises an amplifier for amplifying an input signal. A first differentiation or integration circuit receives an output signal from the amplifier and carries out a primary differentiation or primary integration. A second differentiation or integration circuit is supplied with an output signal from the amplifier and carries out a secondary differentiation or secondary integration. A first gain constant circuit multiplies the output signal from the second differentiation or integration circuit by a first gain constant. A second constant circuit multiplies, by a second gain constant, the signal resulting from the addition of the output signal of the first differentiation or integration circuit and the output signal of the first gain constant circuit. A circuit negatively feeds back, to the amplifier, a signal resulting from the addition of the output signal of the amplifier and the output signal of the second gain constant circuit.

Abstract: An arrangement for electrically heating a semiconductor rod which is simultaneously growing by means of materials deposited from a gas phase, wherein the heating current circuit is formed by a heating current source and an electronic switch which is controllable by a variable auxiliary voltage. The heating current is applied to a smoothing circuit by way of a rectifier circuit which is coupled with the heating current circuit. The initial voltage of the smoothing circuit is compared with a desired voltage and the difference voltage determined by this comparison serves to control the generator which supplies the auxiliary voltage. The smoothing circuit is coupled with a preamplifier whose output is connected with the movable tap of a potentiometer. A fixed terminal of the potentiometer is connected to a source which supplies the desired voltage and to the input of a subsequent control amplifier. Another fixed contact of the potentiometer is connected in a feedback circuit to the input of the preamplifier.