Abstract: An RF power amplifier for delivering power to a load including a first quadrature hybrid coupler driving two class C amplifiers operating with high input compression, a second quadrature hybrid coupler coupled to the outputs of the amplifiers, an attenuator, and a phase shifter. An impedance mismatch by the load causes phase-pulling of the amplifiers which reduces output to the load. This is compensated for by feeding an error signal, indicating the magnitude and phase of the phase-pulling of the two amplifiers, from the second quadrature hybrid coupler through the attenuator and the phase shifter back to the first quadrature hybrid coupler. The attenuated and phase shifted error signal adds to or is subtracted from the input signals to the two amplifiers. Therefore, one of the two amplifiers is driven with more signal and the other amplifier is driven with less signal to phase-push the two amplifiers to compensate for the phase-pulling to thereby increase the output to the load.

Abstract: An audio output amplifying device which is adapted for use in a plurality of audio output amplifying circuits. An audio signal to be amplified is supplied to a positive phase input of a first differential amplifier. The positive phase input of a second differential amplifier is selectively coupled either to a source of a reference voltage (ground) or the source of the audio signal. A feedback circuit is connected between the output of the first differential amplifier and the negative phase inputs of both the first and second differential amplifiers. A switch is provided to selectively couple the output of the first differential amplifier to ground in one position and to allow amplification by both differential amplifiers in a second position.

Abstract: A power amplifier with a low distortion and a high power efficiency includes a first amplifier of the low distortion type for being powered by a first voltage source to amplify an input signal thereto to apply an output signal to a first terminal, and a second amplifier of the high power efficiency type for being powered by a second voltage source to amplify the input signal to apply an output signal to a second terminal. A load is connected between the first and second terminals. The output voltage of the second voltage source is greater than that of the first voltage source. A first feedback path is provided for feeding back the output signal of the first amplifier to an input thereof. A second feedback path is provided for feeding back the output signal of the second amplifier to the input of the first amplifier.

Abstract: A fiber optic amplifier utilizes a crystal fiber of laser material to bidirectionally amplify light signals. This amplifier permits the application of both pumping illumination and the signal to be amplified to the end of the crystal fiber to avoid the disadvantages inherent in side pumping this fiber. End pumping is accomplished by taking advantage of the slow spontaneous fluorescence of the laser crystal to sequentially apply the pumping illumination and then the signal to be amplified to the crystal. This sequential application of signals is made possible through the use of a switchable coupler which allows light to be selectively coupled from either of a pair of input optical fibers to a single output optical fiber which is coupled to the crystal fiber. The pumping illumination is initially supplied to the crystal fiber to invert the ions within the crystal.

Abstract: A semiconductor amplifier circuit includes first and second operational amplifiers, and first and second voltage dividers connected between the outputs of the first and second operational amplifiers, respectively, and a reference potential source. First and second resistors are connected between the divider point of the first and second voltage dividers, respectively, and the inverting input of the first and second operational amplifiers, respectively, forming real negative feedbacks. A first signal input terminal of the amplifier circuit is connected to the non-inverting input of the first and second operational amplifiers, respectively. A third common voltage divider is connected between the reference potential source and a supply potential source. A common intermediate resistor is connected to the divider point of the common voltage divider, and first and second supply resistors are connected in series with the intermediate resistor.

Abstract: A band-pass filter includes an arrangement of individual filter sections and means for weighting and summing the band-pass functions of the filter sections such that the active conjugate pole pairs are arranged in the z plane on a circle concentric to the unit circle and spaced by equal angles with the exception of corrector poles, which are spaced by half-angle increments from the adjacent poles. In the embodiment of the invention described, the filter sections are in the form of digitally controlled switched capacitor filters.

Abstract: A stereo amplifier circuit which comprises a first circuit responsive to a first input signal and to a second input signal for generating a first output signal which corresponds to the potential difference between the first and second input signals, a second circuit responsive to the first and second input signals for generating a second output signal which corresponds to the potential difference between the second and first input signals, a third circuit responsive to the first and second input signals for generating a third output signal which corresponds to the sum of the first and second input signals. The third output signal contains signal components being antiphasic to the first and second input signals.

Abstract: A differential amplifying circuit includes a pair of main amplifying circuits (5a, 5b) each having at least three input terminals and at least one output terminal, and a pair of auxiliary amplifying circuits (6a, 6b) each having at least one input terminal. Complimentary inputs (D1, D1) are connected to the input terminals of said pair of auxiliary amplifying circuits (6a, 6b), the outputs (D2, D2) of the main amplifying circuits (5a, 5b) are connected as crossing feedback inputs to at least a pair of input terminals of said pair of main amplifying circuits (5a, 5b), the complimentary inputs (D2, D2) are also connected to the other at least one pair of input terminals, and the outputs of said auxiliary amplifying circuits (6a, 6b) are further connected to the further at least pair of input terminals.

Abstract: A system input is connected to a positive high voltage signal generator and a negative high voltage signal generator, the outputs of which are each connected to an output terminal via a photoconductor. The photoconductors are driven individually by an energizing circuit which has an input the sum of the system input and an attenuated signal fedback from the output terminal. For system inputs above a first predetermined level or below a second predetermined level, the appropriate photoconductor is rendered heavily conductive so that the output consists of the signal developed by the corresponding signal generator, which is proportional to the system input, less the small voltage drop which occurs across the photoconductor. For system inputs between the two predetermined levels, both high voltage signal generators deliver constant output signals and the energizing circuit reduces the conductivity of the appropriate photoconductor to produce the desired system output.

Abstract: A trigger circuit for use in an oscilloscope comprises a DC amplifier for low frequency amplification and high-frequency amplifier arranged to provide wideband trigger signal amplification while providing typical trigger coupling modes, such as AC, DC, high-frequency reject, and low-frequency reject.

Abstract: By adding the difference between output and input of the one amplifier section to the output signal by means of a subsequent amplifier section a ring of amplifier sections can be formed which compensate for each other's distortion.

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: Frequency characteristic adjusting apparatus used in sound apparatus or the like, in which an input signal is divided into first and second frequency bands after being amplified, the gain of the signal of the first frequency band controlled by first and second gain control circuits respectively, the gain of the signal of the second frequency band controlled by third and fourth gain control circuits respectively, and the output signals from the first and second gain control circuits added and negatively fed back to the amplifier. The output signals from the third and fourth gain control circuits are also added.

Abstract: A BTL power amplifier circuit with substantially zero distortion is disclosed. A distortion detecting circuit is provided which employs a feed forward technique for sensing the distortion generated in one of two amplifiers constituting the BTL power amplifier circuit and then applying to the other of the two amplifiers so as to output the distortion having the same amplitude and polarity as the sensed distortion. The distortions derived from the two amplifiers are fully cancelled out across a load to each other.

Abstract: A multiple band frequency response controller for use in audio applications, to precisely control and equalize audio system response. The frequency response controller shown will adjust response in ten octave bands. The unique feedback system used will generate response curves of increased smoothness and accuracy. In addition, the method shown will be readily adaptable to external control by analog or digital control signals.

Abstract: A general purpose active filter which can be fabricated as a single, monolithic IC. The IC includes two independent filter building blocks. Each filter block includes a pair of serially connected summers and a pair of serially connected switched capacitor positive integrators connected to the serial output of the summers. The IC further includes clock interface circuitry for receiving and conditioning first and second external clock signals. The interface circuitry drives the switches of the positive integrators of each filter block with one of the first and second conditioned clock signals. A plurality of input and output leads are interconnected with the components of each filter block to permit the filter blocks to be separately configured to perform various second order filter functions. The filter blocks may be tuned according to external resistance ratios and/or according to the frequencies of the external clock signals.

Abstract: A bridge audio amplifier is disclosed which includes an input stage for receiving an audio input signal and having a bias amplifier and a signal amplifier which provide a combined output current containing a substantially constant dc component and an ac component which is dependent on the input signal and the relative transconductance of the bias and signal amplifiers. The transconductance of the bias and signal amplifiers is reciprocably varied by a dc control voltage to vary the ac component of the current. The output current is converted to a voltage signal and applied to an output stage for driving a speaker. Two such audio amplifiers driving front and rear speakers may be employed to achieve a low level fade function.

Abstract: A feed-forward amplifier in which samples of the input and output signals a main amplifier are adjusted in amplitude and algebraically combined to produce a sample of the error introduced into the output signal by distortion and noise in the main amplifier. This error sample is amplified to produce a correction signal by a subsidiary amplifier which itself introduces noise and distortion. The correction signal is algebraically combined with the output signal of the main amplifier and a fraction of the resultant output signal is fed back to the input of the subsidiary amplifier to render the output signal substantially free of error caused by either of the main and the subsidiary amplifiers.

Abstract: An amplifying device comprising a pre-amplifier, a first high power amplifier of a relatively bad lineality for amplifying the outputs of the pre-amplifier, a first impedance element for applying the outputs of the first amplifier to a load, a negative feedback circuit for feeding back the outputs of the first amplifier to the input of the pre-amplifier and a second low power amplifier of the relatively good linearity for amplifying the inputs of the first amplifier and supplying the outputs through a second impedance element to the load. The amplifying device can cancel the distortion in the high frequency band caused in the first amplifier through the first and second impedance elements by the outputs of the first amplifier.

Abstract: Two operational amplifiers are hooked in a different mode by unique circuitry so that the common mode gain is unity and the open loop gain is the same as the open loop gain of the individual amplifiers. Essentially, a negative feedback network feeds the common mode output signal back to the negative input terminals which cancels the common mode output signal. Practical applications are achieved by adding appropriate integrating capacitors between the output and negative inputs of the amplifiers with appropriate series resistances in the input leads.

Abstract: A switched-capacitor circuit (50) for passing an audio frequency over a predetermined range of frequencies fabricated on a monolithic semiconductor substrate is provided. The switched-capacitor filter (50) includes a first amplifier (60) and a second amplifier (90). A first integrator capacitor (66) is interconnected to the first amplifier (60). A second integrator capacitor (96) is interconnected to the first amplifier (90). A first input switched-capacitor (82) is interconnected between the first amplifier (60) and the second amplifier (90), such that the first input switched-capacitor (82) samples and holds the output of the second amplifier (90) during a first clock phase thereby isolating the output of the second amplifier (90) from the input of the first amplifier (60). During a second clock phase the first input switched-capacitor (82) applies the output of the second amplifier (90) to the first integrator capacitor (66).

Abstract: An amplifier comprising a first and a second amplifier element, whose outputs are connected to a load, a difference circuit which comprises a comparator, in which the output signal of the first amplifier element is compated with the input signal thereof to produce a correction signal which is applied to second amplifier element, and a second substantially identical difference circuit which comprises a comparator in which the output signal of the second amplifier element is compared with the input signal thereof to produce a correction signal which is applied to the first amplifier element; a desired signal to be amplified being applied to both amplifier elements. The two amplifier elements, which may be preceded by preamplifiers, take the form of power amplifiers. Because the distortion signals appear at the load as "common mode" signals, the overall distortion becomes substantially zero in the case of equal attentuation in the two difference circuits.

Abstract: A current source in which the output current from an output amplifier stage (2) is controlled by an input signal, originating in a signal source (11), to an input amplifier stage (1) incorporates, additionally to a negative feedback path from the current input path of the output stage (2) to the input amplifier (1), monitoring means (5) in the signal input path to the output amplifier (2) and control means (4) in an input path to the input amplifier (1). Monitoring means (5) monitors the current flow in the input path to the output amplifier (2) and applies, via control means (4) a signal to the input amplifier (1) such that the dependence of the current flow in the current output path on the gain of the output stage (2) is reduced. A circuit is described, as well as an application to driving a telephone subscriber line and using two current sources working in push-pull mode.

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: A circuit for converting an asymmetrical input signal applied to a single ended input terminal of the circuit to a symmetrical output voltage appearing across balanced differential outputs. The circuit includes first and second operational amplifiers, the outputs of which are the outputs of the circuit. The noninverting inputs of the two amplifiers being coupled to a reference voltage. The inverting input of the first amplifier being adapted to receive the input signal and further being coupled through a first resistor to the output thereof. The inverting input of the second amplifier being coupled both to the output thereof and the output of the first amplifier through respective second and third resistors.

Abstract: A differential amplifier circuit comprised of two operational amplifiers for use as a differential output and differential input amplifier for any two-terminal impedance transfer function. The input impedance is very low between the two input terminals, yet it is very high between either input terminal and the common or ground terminal, thus giving this amplifier many of the desirable characteristics of a transformer-coupled amplifier. High common mode voltage rejection ratios can be achieved even when moderate differential imbalances exist in the input and feedback networks due to the unique balancing feature of the circuit.

Abstract: A seismic amplifier for use in marine seismic survey work involving the transmission of signals from remote signalling stations over cable pairs to signal processing equipment. These signalling stations are comprised of capacitive transducers. The seismic amplifier of the surveying system includes operational amplifiers electrically interconnected with a feedback circuit comprised of a balanced resistive-reactive network which is a lumped parameter equivalent circuit of the transmission line and capacitive transducer. The lumped parameter equivalent circuit used for feedback provides a flat, zero-phase shift overall response over the cable pair from the transducer to the output of a differential amplifier stage which is connected to the operational amplifier outputs to improve common mode rejection.

Abstract: A synchro buffer amplifier is provided which uses two matched amplifiers respectively connected to the primary windings of two transformers. Two input leads are respectively connected to the inputs of the two amplifiers and a third input lead is grounded. The secondary windings of the two transformers are connected in series, and three output leads are respectively connected to the other sides of the two secondary windings and to the common secondary connection. Direct feedback is provided for each amplifier. Any circuit unbalance is compensated by the insertion of a low value choke in the common transformer secondary connection. Three capacitors are connected across the respective output leads partially to tune the loads, and thereby to nullify to some extent the effects of heavy inductive loads so as to allow operation of the buffer amplifier over a wider range of loads than would otherwise be possible.

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 high voltage/high current circuitry includes a push-pull voltage amplification stage connected in tandem with a parallel connected push-pull current amplification stage. For the voltage amplification stage a pair of bipolar operational amplifiers are connected in parallel and operate in a push-pull manner. A pair of switching means are positioned at the output of each of the bipolar operational amplifiers while the outputs of the amplifiers are connected to the inputs through a current gain regulating means, an isolation means and a voltage divider means.

Abstract: A differential amplifying circuit eliminates the common mode component of a composite signal consisting of the common mode component and a differential component. Two differential amplifiers are coupled to a composite signal source so that one amplifier amplifies only the differential component and transfers the common mode component unchanged. The other amplifier processes the common mode component. The outputs of the differential amplifiers are connected to a voltage divider. The output of the circuit is taken from a tap on this voltage divider at a point where the common mode component is eliminated so that only the amplified differential component remains.

Abstract: A low noise differential amplifier circuit which requires only two operational amplifiers and which has lower noise than conventional differential amplifiers. An alternate embodiment is disclosed including circuitry for autozeroing the amplifier.

Abstract: The amplifier system comprises a pair of operational amplifiers with an appropriate resistance network such that when a reference voltage and differential signal are applied to the system, changes in the gain of the amplifier system will only change the gain of the differential signal and will not affect the reference voltage.

Abstract: An amplifier having a plurality of cascaded stages each comprising an operational amplifier having an output connected to a first output terminal of the amplifier through two series-connected resistors and a capacitor, the junction point of the two resistors being connected to the negative input of the operational amplifier, and the junction point of the capacitor and one of the series-connected resistors being connected to the positive input of a next operational amplifier, the output of each operational amplifier being additionally connected to said first output terminal through a variable resistor having a movable contact connected to the second output terminal of the amplifier.

Abstract: An operational amplifier driver circuit for supplying an undistorted ac signal to a resistive load connected across a balanced pair of twisted transmission lines where the balanced lines have common mode noise signals thereon due to the presence of substantial noise of an external, uncontrolled nature. The driver circuit includes a pair of operational amplifiers interconnected to utilize the common mode noise signals in feedback paths thereof whereby the operational amplifiers are able to operate in their linear ranges even in the presence of high levels of common mode signals on the balanced lines, thereby compensating for the effects of the common mode noise signals on the balanced lines.

Abstract: A plurality of similar power amplifier circuits are connected in parallel in the output of an amplifier between the amplifier's voltage amplifier circuit and the load. Each of these amplifier circuits has a similar ballasting resistor connected between its output and the load. The amplifier circuits have unity closed loop voltage gain. The value of the ballasting resistors is empirically chosen such that these resistors are capable of accommodating differences in the outputs of the amplifier circuits which may occur, such that the load is equally shared between the amplifier circuits.

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: An unconditionally stable gyrator circuit includes two interconnected d.c. differential amplifiers. The terminals of an input port are respectively connected to the non-inverting inputs of the amplifiers, that to the second amplifier being connected through a resistor. The inverting input of the first amplifier is connected to the non-inverting input of the second, the output of the first amplifier is connected through a resistor to the inverting input of the second amplifier and the output of the second amplifier is connected through a resistor to the non-inverting input of the first amplifier. Two alternative output ports are provided between the output of the first amplifier and the non-inverting input of the second, and between the output of the second amplifier and its inverting input. The output port which is not used has a resistive impedance connected across it.

Abstract: In differential input DC gain amplifiers with high input impedance, a capacitive attenuator is built-in in order to reduce the amplifying effect on the AC component due to interference by the industrial power lines. Such attenuation is obtained by feeding back through cross capacitors the AC signal at one output to the input on the opposite side so that the ratio of the differential outputs to the differential inputs for the AC component is substantially unity.

Abstract: Audio signals are equally power divided with the power divided signals being 180.degree. out-of-phase. These separate out-of-phase signals are separately applied to the inverting input of separate current-differencing type operational amplifiers wherein the out-of-phase signals are separately amplified. The separate operational amplifiers are individually connected to a different one of two amplifiers connected in push-pull. Muting of this audio output is achieved by passing a large DC current to the inverting input of the separate operational amplifiers simultaneously whereby the output level therefrom drops to a level that biases the push-pull amplifiers off.

Abstract: A feedback amplifier including a first and a second amplifier section comprises an autotransformer winding connected between common terminals of the respective amplifier sections and across a feedback circuit. A terminating impedance is connected between the output terminal of one of the amplifier sections and the autotransformer winding at a point nearer to its point of connection to the other amplifier section common terminal. Another terminating impedance is connected between the other amplifier section output terminal and the autotransformer winding at another point nearer to its point of connection to the common terminal of the above-mentioned one amplifier section. The terminating impedances may be used on the input side. They may be connected to the autotransformer winding at its points of connection to the respective common terminals, when the autotransformer may be dispensed with.

Abstract: An active dual channel tuning control particularly useful for television and stereo applications has two independently adjustable channels. For example, each channel for stereo has an input for receiving a decoded signal which represents the left or right channel information. Each channel additionally has a feedback amplifier with an adjustably turned output to permit highly selective tuning and impedance matching to the following amplification stages. Switching networks are provided for reversing the channel outputs as well as for selectively inhibiting either of the channel outputs in either the normal or reversed channel condition.

Abstract: A differential voltage amplifier having high gain and a wide bandwidth essentially comprises an unstable circuit having one position of unstable equilibrium and two distinct positions of equilibrium which can be maintained for a given period of time, an input stage for applying signals to the input of said unstable circuit for a given period of time, means for returning the unstable circuit to its position of unstable equilibrium, means for calibrating the output of the unstable circuit at the voltage +V.sub.m or at the voltage -V.sub.m according to the position of unstable equilibrium, means for integrating the calibrated signal which appears at the output of the bistable circuit for a given period of time and a clock for the synchronization of the entire circuit.

Abstract: An anti-skid brake control system having two wheel velocity pick-up coils connected to respective common mode rejection circuits. A coil open detector including a Norton amplifier is also connected from the said circuits to disable the system controller should an open develop in one of the pick-up coils.

Abstract: A distortion-free amplifier for electric signals has a high-quality low-power amplifier-section. In addition there is a high-power amplifier-section which delivers the majority of the current to the load. A feedback signal is derived which is a measure of the output current of the high-power section and not the low-power section. The feedback signal is applied to the inputs of both amplifier-sections negatively in an amount such as to remove from the combined output currents in the load any distortion occurring in the contribution from the high-power section.

Abstract: A reverberation device is provided with a delay line in series with an amplifier which is designed to compensate for the inherent frequency dependent attenuation of the delay line. The output of the compensating amplifier is fed back directly to the delay line input.

Abstract: The invention provides a circuit for an all-pass reverberator with an MOS delay line and feed back amplifier. The circuit compensates for the frequency-dependent attenuation of the delay line. Two amplifiers of the prior art circuit are replaced by resistors and a third one has specific characteristics.