Abstract: A low distortion amplifier arrangement includes an amplifier having an inverting input, a non-inverting input, and an output, a first impedance coupled between the output and the inverting input, and a second impedance coupled between an input terminal of the amplifier arrangement and the amplifier inverting input. An impedance network is coupled between the inverting and the non-inverting inputs of the amplifier. The impedance value of said impedance network substantially corresponds to the impedance value of the parallel connection of the first impedance and the second impedance, but with opposite sign. The gain of the amplifier arrangement is independent of the gain of the amplifier and corresponds to the ratio of the impedance values of said first and second impedances to produce an amplifier arrangement with a very low distortion.

Abstract: The adverse effects of the impedance of long varying impedance connecting lines used in pulse width modulated power amplifier are eliminated by means of a dual input differential amplifier that senses the line voltage drops in the connecting lines and combines them into a line voltage drop compensation signal that is applied across the power amplifier inputs. This line voltage drop compensation signal raises the output of the power amplifier by the amounts needed to null out the line voltage drops.

Abstract: An electronic transformer is characterized by a pair of out of phase and bilateral current sources, the outputs from which are opposite in phase and control voltages across and currents through respective source and load impedances by combining the voltages in opposition through an amplifier that controls each current source. The electronic transformer has some properties which are essentially the same as those of a conventional magnetic transformer, except that there advantageously is no magnetic field and unwanted magnetic coupling with adjacent components, and the equivalents of leakage reactance, mutual reactance, turns ratio and/or impedance matching may be conveniently and accurately electronically controlled. In addition, the electronic transformer can readily be operated as a switched gain amplifier source, a negative impedance amplifier and/or a positive impedance network generator.

Abstract: A wide-band direct-current coupled transistor amplifier is provided which exhibits uniform gain in a frequency range from direct-current to greater than 100 MHz, and which exhibits other desirable features.

Abstract: An electric amplifier adapted to respond to an input signal of either polarity comprising a first differential amplifier OP1 which is arranged to drive through a load L a current whose value varies with the input but is independent of the load value and a second differential amplifier OP2 arranged to maintain the ratio of the amplifier output potentials relative to a datum potential at a predetermined value so that by appropriate choice of the datum potential and the predetermined ratio value the available output potential swing with a given supply voltage can be maximized.

Abstract: In a frequency characteristic adjusting circuit having an arrangement of at least one adder, a filter circuit and feedback and/or feed forward means the transfer factors of which and the peak or dip of the filter circuit are freely selectable. Adjustment of the center frequency and Q are independent.

Abstract: A non-inverting amplifier circuit having input and output terminals wherein the input impedance between the input terminal and a reference point is relatively low. The circuit comprises a first amplifier having a non-inverting input coupled to the input terminal, an inverting input, and an output coupled to the output terminal. A second amplifier is also provided, the second amplifier having a non-inverting input, an inverting input coupled to the output of the first amplifier and an output coupled to the non-inverting input of the first amplifier.

Abstract: A dynamic equalizer circuit is disclosed for the driver system of an electro-mechanical transducer such as a loudspeaker. The circuit provides an improved or leveled audio output and includes a protective arrangement which protects the transducer against damage from being overdriven. The protective arrangement includes a sensor which produces a continuous protective control signal based upon operating characteristics of the transducer such as transducer motion or temperature or fatigue.

Abstract: A device for analyzing and linearizing the frequency characteristics of electrical signals from unknown systems consists of identically constructed modules with variable transfer functions, which transfer functions are to be adjusted to a inverse component of the electrical signal to be analyzed. A procedure is disclosed in which the time constant and variable gain of each module is independently adjusted, whereby the variable gains and the time constants define the poles and the zeros of a polynomial, which polynomial describes the frequency characteristics of the unknown system.

Abstract: A positive feedback RC active biquadratic filter circuit comprising a passive input RC section and an active amplification output section having at least one operational amplifier. The RC section has two true resistive T-networks and a true capacitive T-network connected to receive an input signal. The RC section realizes a second order function with a low Q factor. The operational amplifier has a feedback resistive connection from an output thereof to a mid-junction point between each of three capacitances in the capacitive T-network. The capacitive T-network and one of the two resistive T-networks are connected to a positive input of the operational amplifier. The other resistive T-network is connected to a negative input of the operational amplifier.

Abstract: In an equalizer amplifier of RC attenuation type comprising an RC circuit having RIAA reproduction characteristics, the RC circuit is connected between an input of a first amplifier for amplifying an output signal of the RC circuit and an output of a second amplifier for amplifying an output signal of the first amplifier. One of the amplifiers is a noninverting amplifier, and the other is an inverting amplifier. So constituted, the equalizer amplifier increases apparently impedances of RC elements connected between the input of the first amplifier and the output of the second amplifier and permits the use of a capacitor of a smaller capacitance value which has good electrical characteristics.

Abstract: A voltage-to-current converter circuit comprises first and second amplifiers each having a noninverting input, an inverting input and an output, the noninverting inputs of the first and second amplifiers being respectively connected to an input terminal for receiving an input signal and circuit ground, a first impedance element connected between the inverting input of the first amplifier and circuit ground, a second impedance element connected between the output and the inverting input of the first amplifier, a third impedance element connected between the output of the i first amplifier and an output terminal to be connected to a load, a fourth impedance element connected between the inverting input of the second amplifier and the output terminal, a fifth impedance element connected between the output and the inverting input of the second amplifier, and a sixth impedance element connected between the output of second amplifier and the inverting input of first amplifier.

Abstract: A frequency region split type noise reducing apparatus, comprising a compressor and an expander; the compressor (or the expander) including a plurality of frequency region splitting filters for splitting the frequency range of the signal into a plurality of frequency regions, a plurality of level sensors for detecting the levels of the signals in the respective frequency regions split by the plurality of filters, a plurality of voltage controlled amlifiers responsive to the level detected outputs of the corresponding level sensors for linearly compressing (or expanding) in terms of a logarithmic scale the dynamic range of the signal, and an adder for adding the outputs as compressed by the voltage controlled amplifiers for providing a composite signal, and the expander (or the compressor) including an amplifier and a switch circuit for connecting the compressor (or expander) to the amplifier to form a negative feedback circuit, whereby the expander (or the compressor) is implemented by a negative feedback amp

Abstract: A frequency response characteristic adjustable circuit which is comprised of first and second operational amplifiers, a potentiometer, a filter circuit having a lowpass, highpass or bandpass characteristic and resistors and suited for a tone control circuit in an audio amplifier system. The frequency range, over which the circuit gain is to be controlled, is determined by the frequency characteristic of the filter circuit, and the circuit gain is controlled by adjusting the potentiometer without affecting the frequency range.

Abstract: A tone control circuit device including a plurality of bandpass filters connected in parallel with one another with each of the bandpass filters having a different center frequency and each being variable in order to vary the tone as in a graphic equalizer. In one embodiment, the output signals from the bandpass filters are coupled both to non-inverting input terminals of output and input signal summers. The input signal is coupled to another input of the input signal summer and the combined signals coupled to inputs of each of the bandpass filters and to a non-inverting terminal of the output signal summer. In another embodiment, plural characteristic circuits, each including a band-stop filter, are connected in parallel between input and output signal summers through a disclosed amplifier network. With this invention, a graphic equalizer tone control device can be constructed which is essentially free from noise and which has a very low distortion factor.

Abstract: Two high voltage power supplies programmable by external voltage and each having their positive output terminals as common are combined so that the output has the negative terminal grounded. Also the input programming voltage is applied referenced to ground.

Abstract: A pulsed voltage amplification device with drift correction comprises a main differential amplifier whose non-inverting input is coupled to a pulsed voltage source, this main differential amplifier being provided with a pulsed feedback circuit coupled to the output and the inverting input of the main differential amplifier, and a memory capacitor coupled to the inverting input of the main differential amplifier. The pulsed feedback circuit comprises an additional differential amplifier, having its non-inverting input coupled to the output of the main differential amplifier, and a diode connected in series with the additional differential amplifier and coupled to the inverting input of the main differential amplifier. The operation of the proposed device in conjunction with various amplitude analyzers makes it possible to enhance the validity and accuracy of the analysis results, to simplify circuit requirements and to increase circuit reliability.

Abstract: According to the present invention circuit means and method are provided which correct for variations in an amplifier load such as a speaker by sensing the load current, developing a feedback signal related to the load current, comparing this feedback signal with the amplifier program, and instantaneously adjusting the gain of the amplifier to compensate for load current deviations from the program applied to the amplifier. By this means the performance of the speaker or other load that is driven by the amplifier is positively controlled and forced to track accurately with the program applied to the amplifier despite such opposing factors as reactance or inertia of the load, whereby the acoustic or other load response is a substantially accurate reproduction of the program.

Abstract: A narrow-band RC active bandpass filter, in which the center frequency may be changed by changing the resistance values of certain resistive elements, has the certain resistive elements switchably connectable into and out of the RC network so that the ratio of time during which the resistors are connected to the network to the time during which resistors are not connected to the network determines the effective resistance thereof. A programmable timing circuit has a plurality of outputs with each output supplying a different number of equal width pulses during a predetermined like time period whereby each output corresponds to a different ratio. The timing circuit actuates and deactuates the switchable connection from a selected output thus deriving the required effective resistance for a predetermined center frequency.

Abstract: An amplitude equalizer circuit utilizing active components in which unidirectional functional tuning of the amplitude, bandwidth and center frequency, may each be adjusted by varying a single resistance for each parameter. This eliminates the need for ganged-potentiometers or altering a plurality of interacting components.

Abstract: The disclosed deviation driver circuit is capable of producing a difference voltage having a magnitude related to the voltage of a deviation signal provided to the circuit from an external source. The deviation driver circuit of the present invention is comprised of a differential amplifier with negative feedback. This differential amplifier includes a pair of transistors and a plurality of load resistors which are arranged to form a balanced bridged network. Since one input of the differential amplifier is electrically connected to ground, this amplifier generates a difference voltage having a magnitude related to the voltage of the signal provided to the active input of the amplifier. The feedback loop, on the other hand, includes another differential amplifier which is interconnected with the first mentioned differential amplifier to produce a feedback signal having a voltage level related to the magnitude of the difference voltage produced by the first mentioned differential amplifier.

Abstract: A pre-amplifier for photomultiplier tubes includes means to compensate for the combined dark current and noise output of a photomultiplier tube without inducing a noise dependent offset voltage at the pre-amplifier output. A feedback amplifier and a compensating network, including a capacitor, cooperate to monitor the pre-amplifier output and during this time to maintain the feedback amplifier in a linearly responsive state while charging the capacitor to an amount necessary to clamp the average value of the most negative excursion of the pre-amplifier output to ground.

Abstract: A power amplifier device comprising first and second output terminals connected to a loudspeaker, and a power amplifier having a non-inverting input supplied with an audio signal, an output connected to the first output terminal and an inverting input. The second output terminal is grounded through a first resistor and connected to an input of an inverting amplifier having a gain of -1. An output of the inverting amplifier is connected to the inverting input of the power amplifier through a second resistor. The output of the power amplifier is connected to its inverting input through a third resistor. The ratio of the third resistor to the second resistor is selected to be larger than 1 whereby the output impedance of the power amplifier device as seen from the first and second output terminals is made to be negative.

Abstract: In an amplifier device having a resistor inserted between an input terminal and the ground, a signal whose phase is opposite to that of an input signal is applied to the resistor, whereby the effect of thermal noise which may be generated by the resistor is minimized to improve the S/N ratio.

Abstract: A compander system is described, in which the `compression` and `expansion` modes are established by the selective use of a compression or expansion circuit as such or as a negative feed-back branch for a back-coupled amplifier.

Abstract: Signal currents corresponding to a voltage to be converted into current or to a current to be amplified are applied to one input of an operational amplifier and its other input is referenced to ground. Its output is connected via a power amplifier and a small resistance to an output terminal and means are provided for supplying current proportional to the voltage across the resistance to the signal input of the operational amplifier with such polarity as to tend to cancel the signal current present thereat.

Abstract: A control device for controlling the emission current of an x-ray tube comprising a control circuit which receives a digital reference value signal and an amplifier whose gain is controlled by a portion of said digital reference value signal so as to provide a comparatively high accuracy for the emission current adjustment with a minimum number of binary positions.

Abstract: The circuitry is arranged to develop a highly accurate and stable reference electric level voltage and/or current for distribution to a plurality of logical circuits on a semiconductor chip having of the order of a thousand such circuits thereon. An input reference voltage is developed by a source reference circuit and applied to an operational amplifier circuit having "evener" circuitry for substantially equalizing the currents in the input transistors. This evener circuitry is essentially an operational amplifier within an op-amp. It monitors and adjusts feedback voltages. The operational amplifier and evener circuitry drives a reference voltage distribution grid laid out over the semiconductor chip.

Abstract: Feedback elimination apparatus for a sound system which includes a notch filter assembly comprising a plurality of active notch filters connected in parallel with one another. Each of the notch filters is formed of a loop amplifier circuit including an operational amplifier having a resonant feedback network so arranged that in the normal mode an auxiliary signal peaked at the resonant frequency is applied out-of-phase to the system, thereby to establish a notch in the frequency characteristic curve of the system. An improved loop circuit is used to produce a notch which is sharp and well defined, with auxiliary circuitry for aligning the notch with a feedback signal. In the preferred embodiment means are provided for temporarily switching the notch filter into an oscillating mode in which it oscillates at notch frequency to produce an audible reference signal.

Abstract: An electronic circuit including an amplifier having an input adapted for coupling to an analog signal source; a current source coupled to the output of the amplifier; a feedback transistor having a collector electrode and emitter electrode connected in series between the output of the current source and the input of the amplifier; and a lead network, including a capacitor connected between the input and output of the amplifier, for stabilizing the electronic circuit. With such arrangement the current in the collector electrode of the feedback transistor rapidly becomes related to current fed to the input of the amplifier by the analog signal source.

Abstract: An active filter is disclosed for providing improved notch and band pass filters. The output to input frequency response of an active filter is mathematically expressed as a ratio of two polynominals in the Laplace operator S. In any notch filter, the coefficient of the S term in the numerator must be reduced to zero, while in any band pass arrangement the coefficient of the S term in the denominator is reduced to zero. The improved notch filter provides an input circuit for the operational amplifier portion of the filter which eliminates the S term in the numerator so that adjustments to reduce this term are unnecessary. Similarly, in the improved band pass filter, the S term in the denominator is eliminated in the feedback circuit provided for the operational amplifier, so that adjustment is unnecessary to eliminate the coefficient of S.

Abstract: Circuits are disclosed for normalizing a device which has a current-controlled frequency response, such as a YIG or a TWM device, to a predetermined current-frequency (I-F) characteristic in order that a device equipped with such a circuit can be preadjusted for substitution in a system for a like device without realigning the system. The normalizing circuit is in parallel with the device, and is comprised of a transistor and a compensating current-sensing resistor in series with the transistor. A shunt compensating current, I.sub.C, through the transistor is set by a voltage on a potentiometer to offset the I-F characteristic of the composite device and circuit from that of the device to a predetermined level and also by a feedback control circuit connected to the compensating current-sensing resistor. The slope of the offset characteristic is then adjusted to a predetermined value by adjusting the gain of a feedback control circuit between the transistor and a resistor which senses a voltage, V.sub.

Abstract: An improved fast-recovery circuit for ECG amplifiers and the like. The fast-recovery circuit includes threshold responsive circuitry connected in parallel with part of the resistance associated with the integrator in a feedback circuit of the amplifier. The threshold responsive circuitry operates to increase feedback frequency response of the integrator when the normally very low frequency output signal of the amplifier exceeds a certain threshold. The improved circuit prevents the threshold circuitry from responding to pulses or excursions in the output signal of a relatively higher frequency content and which exceed the amplitude threshold for less than a predetermined interval, as for instance caused by pacer spikes, large QRS complexes and the like. Preferably, the improved threshold responsive means comprises transistor means connected across the integrator's resistance and having capacitance means across the base-emitter circuit thereof for inhibiting response to certain short duration signals.

Abstract: The auxilliary signal path in a compander system includes, in series, a first amplifier 7, a weighting function amplifier 8, and a detection circuit 9. The output of the latter controls the gain of a voltage-controlled variable gain circuit 11 also connected to the first amplifier output, and the integrated output of the variable gain circuit is fed back to the input of the first amplifier via a subtraction circuit 13 also supplied with the auxilliary signal path input. Alternatively, the first amplifier may comprise an operational amplifier, in which case the integrated signal is directly coupled to one of its inputs.

Abstract: In a multiplex decoder circuit comprising two pairs of transistor differential circuits driven by switching signals of a 38 kHz subcarrier signal, for separating a stereo composite signal into left and right channel signals, a differential amplifier formed of a pair of transistors connected to the respective differential circuits for amplifying and injecting the composite signal, and a constant current source, at least one of the pair of differential transistor amplifiers being supplied with the composite signal is formed of a negative feedback amplifier to suppress the output distortion of the transistor amplifier due to variations in the emitter resistance of the transistor amplifier with respect to the variations of the input stereo composite signal. As a result, the waveform distortion of the separated left and right channel signals is reduced.

Abstract: A sample and hold circuit is disclosed which employs a matched pair of operational amplifiers as a decoupling circuit to isolate the output of the sample and hold circuit from the sampling capacitor. Prior art decoupling circuits employ a simple isolation amplifier which has a tendency to charge the sampling capacitor with the isolation amplifier input bias and leakage currents. The disclosed decoupling circuit employs one of a pair of matched operational amplifiers as a compensation circuit to dynamically generate the bias and leakage currents found at the input of the other operational amplifier, which is employed as the sample and hold isolation amplifier. Thus, the net quiescent current into the input of the decoupling circuit is zero, thereby eliminating the capacitor charging problem of prior art isolation amplifiers.

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: The invention covers an amplifier circuit in which the output is limited in either polarity. Normally, a part of the output voltage is fed back to the input to maintain linearity but when the output reaches a maximum or minimum value, any further departure is amplified and fed back to the input circuit to neutralize the part of input signals which is outside of the range to be amplified. The feedback amplifier can be designed to initiate limiting at any desired output voltages and the positive and negative output limit voltages can be asymmetric with respect to the quiescent output voltage.

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 self biasing low input impedance differential amplifier for current mode applications requiring wide bandwidth with response down to DC. A shunt-shunt differential mode feedback system in combination with a series-shunt common mode feedback system is connected between an input amplifier stage and an output amplifier stage. An additional shunt-series common mode feedback signal is applied to the input stage to short out the common mode component of the amplifier input signal and minimize input signal drift. High open loop gain in the differential feedback loop provides low impedance amplifier inputs.

Abstract: A differential amplifier is arranged to amplify faithfully the voltage produced by an ungrounded voltage source to provide the amplified result as a voltage in relation to a reference (ground) voltage. Errors resulting from leakage resistances between the ungrounded voltage source and ground are avoided by providing an inverting amplifier responsive to the output voltage, which draws, through a resistance, a current from a terminal of the voltage source which is proportional to the output voltage of the differential amplifier. This causes a shift of the potential of the voltage source in the direction towards the reference voltage. Optimum results are obtained when the shift is such that the variations in the voltage source being observed are caused to become balanced in relation to the reference potential.

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 circuit for correcting an AC output signal from an electronic device into closer correspondence with an AC input signal to the combination of the circuit and device comprises first and second amplifiers arranged to each receive the input signal. The first amplifier is also arranged to receive feedback of the output signal from the electronic device for providing a signal which is a function of the difference between the input and output signals. The combination of signals from the first and second amplifiers is provided to the electronic device for producing an output signal which corresponds closely to the input signal.In a method of operating the circuit with an electronic device from which the output signal variably differs from the input signal, the amplitude of the output signal fed back into the first amplifier is adjusted to provide a null AC signal from the first amplifer at the output signal which deviates least from that desired.

Abstract: First, second, and third single-input, single-output operational amplifiers having associated input resistors and feedback resistors are connected in series between input and output terminals. First and second capacitors are also connected across associated first and second amplifiers to provide a second-order network transfer function. A fourth feedback resistor is connected between the output terminal of the third amplifier and the amplifier side of the first input resistor. The amplifier input sides of the second and third input resistors are also connected through associated feed-forward resistors to the one side of the first input resistor that is spaced from the first amplifier. Appropriate selection of element values enables synthesis of circuits having prescribed biquadratic transfer functions.

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: 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 digitally tuned active filter is disclosed. The filter is tunable by digitally controlling the variable conductance which comprises two resistors, one of which is in series with a field-effect transistor switch and those two in parallel with the other resistor. The field-effect transistor switch is switched by a digitally controlled variable duty cycle generator.

Abstract: An electronic filter circuit comprised of summing circuits and integrating circuits is interconnected such that the filter may use the same components to serve either as a band-reject or a band-pass filter having the same natural frequency. Changing of the filter operation between the two modes is accomplished simply by the interchange of two component values.

Abstract: In a floating electrical output circuit according to co-pending application Ser. No. 395,608, now U.S. Pat. No. 3,909,737, issued Sept. 30, 1975, two load terminals are driven from amplifying means having differential current outputs. A differential amplifier connected across the load terminals provides a feedback signal which is compared with the input signal to provide a control signal for the amplifying means.In the present invention the amplifying means are simplified to a single differential current amplifier.

Abstract: A circuit for cancelling the offset voltage of a signal amplifier includes a second amplifier and a third amplifier connected to the outputs of the signal amplifier and the second amplifier. A capacitor is connected between the inputs of the second amplifier for storing the offset voltages of the amplifiers thereon. A switch connects the output of the third amplifier to the capacitor and a switch connects the inputs of the signal amplifier together during offset correction. When the offset voltages are stored on the capacitor, the switches open to permit signal amplification and cancellation of the offset voltages. In a second embodiment, a second capacitor stores the instantaneous amplitude of the signal being amplified and supplies it to an input of the second amplifier such that a discontinuity will not appear in the circuit output during offset correction.