Abstract: An active load impedance control system for a radio frequency power amplifier comprising an amplification means for amplifying radio frequency signals and providing a forward signal, a control means responsive to the operating conditions of said amplification means, a correction signal means responsive to the control means for providing an amplitude, a sampling means and phase controlled corrective reflective signal and a combining means for combining said forward signal and said corrective reflective signal.

Abstract: A gain-equalized balanced microwave transistor amplifier configuration is disclosed. Two microwave amplifier circuits provide the power amplification. An input power divider divides the input signal into two signal components which are fed to the respective amplifier circuits by two transmission lines. The outputs for the amplifier circuits are fed to an output combiner by two additional transmission lines to provide a combined output signal. The desired gain equalization is provided through the loss of power due to phase error introduced by unequal transmission line lengths connecting the microwave transistor amplifiers to the output power combiner.

Abstract: In an integrated amplifier comprising at least a pair of operational amplifiers which may be connected in a single-ended configuration to form a stereo amplifier or alternatively in a bridge configuration to increase the output dynamics, a single constant current generator for generating a current having a value which is twice the value of the bias current of the input stages of the two operational amplifiers, is connected between an inverting input of one of the two operational amplifiers and ground, and allows for elimination of the offset voltage without contributing to an increase, in any appreciable way, of the noise level at the inputs and without the signal applied to the input terminals of the integrated amplifier causing modulation problems.

Abstract: A so-called bridge audio amplifier, particularly for stereophonic car radio sets, comprises a first power amplifier in a non-inverting configuration which is connected to a second amplifier in an inverting configuration. This audio amplifier further comprises a first resistor pair forming a bridge circuit with the resistors of the first power amplifier, as well as a second resistor pair interconnected between a positive supply pole and ground and with the first and second amplifiers having their respective non-inverting inputs connected across the second resistor pair via respective input resistors. The audio amplifier of this invention requires but a very small number of input pins and may be used as a stereophonic amplifier.

Abstract: A voltage limiting circuit is disclosed for preventing distortion in amplified audio signals. Clipping of the output of a power amplifier is detected and a clipping signal is integrated in a two-step process for limiting a bass frequency gain and limiting a wideband frequency gain which are applied in series. Separate limiting thresholds cause the bass gain to be limited first. Wideband gain is reduced at higher levels of clipping but is more quickly restored when clipping stops. Voltage limiting feedback is provided using inexpensive RC integrator circuits.

Abstract: A sum/differential signal processing circuit for use in a sound reproduction system, such as a Dolby surround processing system, includes a pair of operational amplifiers, a resistor connected between the inverting input terminals of the operational amplifiers, two resistors connected between the output terminals of the operational amplifiers, a signal output terminal connected to a junction between the two resistors for producing the sum of output signals from the output terminals of the operational amplifiers. A make switch is connected across one of the two resistors, which is selectively rendered ON and OFF. When the make switch is ON, the sum of output signals of the operational amplifiers is derived from the signal output terminal while when the make switch is OFF, the difference between the output signals thereof is derived therefrom. Even when a monaural signal is applied to each of the two signal input terminals, the signal is not cancelled by the circuit thus arranged.

Abstract: A switching device is realized by means of two amplifier paths which are controllable by means of transistors. The collectors of output transistors (T1, T1B) are connected together, without an impedance matching circuit for each path, to a common point (10) being connected to an impedance matching circuit (L5, R7) which is common for the two paths. This switching device is particularly used for selecting signal paths between 1 and 2 GHz in systems for receiving television signals by satellite.

Abstract: Attenuator having a high input impedance and several switching levels for high frequencies and oscilloscope and active probe comprising such an attenuator. A high frequency attenuator (15) having a high input impedance and several switching stages intended to attenuate a high-frequency electric signal introduced at an input terminal (10) of the attenuator. The attenuator supplies at a low-impedance output terminal (11) an output signal corresponding to the attenuated input signal. The attenuator comprises k broadband amplifiers A.sub.n (1.ltoreq.n.ltoreq.k) having a very small input capacitance, capacitances D.sub.n arranged between each input and each output of each amplifier, and capacitances C.sub.n arranged between each input of each amplifier and the input terminal of the attenuator. The accurate attenuation switching levels are obtained by using different ratios C.sub.n /D.sub.

Abstract: A satellite communications system employs separate subsystems for providing broadcast and point-to-point two-way communications using the same assigned frequency band. The broadcast and point-to-point subsystems employ an integrated satellite antenna system which uses a common reflector (12). The point-to-point subsystem achieves increased communication capacity through the reuse of the assigned frequency band over multiple, contiguous zones (32, 34, 36, 38) covering the area of the earth to be serviced. Small aperture terminals in the zones are serviced by a plurality of high gain downlink fan beams (29) steered in the east-west direction by frequency address. A special beam-forming network (98) provides in conjunction with an array antenna (20) the multiple zone frequency address function. The satellite (10) employs a filter interconnection matrix (90) for connecting earth terminals in different zones in a manner which permits multiple reuse of the entire band of assigned frequencies.

Abstract: A high efficiency envelope amplifier is disclosed. The invention includes a power supply, a comparator and several switches. The power supply is capable of providing multiple outputs. The comparator measures the amplitude of an input signal against one of several threshold levels. When the input signal is within a predetermined range, a selected power supply output is switched incrementally switches small amounts of power, switching losses are substantially mitigated.

Abstract: The instrumentation amplifier with minimized offset voltage and drift has a very high speed and accuracy. One voltage controlled amplifier operating under open loop condition is interchangeably amplifying the input signal and providing the output signal. Simultaneously, a comparator circuit is automatically correcting the gain and error voltage of another voltage controlled amplifier by adjusting voltages across two capacitors coupled thereto. The accuracy of a reference source, passive components and on-resistance of switches is not essential. Amplifiers with FET input stages and an output buffer amplifier can be employed. The gain of the instrumentation amplifier is set by a voltage or digitally.

Abstract: An equal power amplifier system (100) for amplifying a plurality of signals for transmission by an active phase array antenna (20), and a compact plural level beam-forming network (98) for forming a plurality of such signals, for example on excitation patterns for frequency scanned virtual beams, are disclosed. The amplifier system uses at most only a few sizes of power amplifiers (130, 134) to amplify efficiently numerous signals having significantly different amplitudes. This is accomplished by distributing the task of amplifying signal pairs (A.sub.i, B.sub.i) composed of one large amplitude signal and one small amplitude signal to an equal power amplifying apparatus (130; 230), which includes two hybrid couplers (236, 238) and two equally sized power amplifiers (232, 234). The first hybrid coupler (236) divides the two signals (A.sub.i, B.sub.i) for input into the two power amplifiers.

Abstract: Reduction of undesired r.f. harmonics, generated in the highest power power amplifier of a transmitter, is achieved by providing at least one alternate path for the undesired harmonics incorporating a relatively low powered power amplifier for at least one undesired harmonic component and causing the harmonic, in this alternate path, to have an amplitude that is substantially equal and a phase 180 degrees relative to the corresponding harmonic output from the main path and combining the outputs of the paths.

Abstract: A plurality of amplifier channels, wherein each channel is automatically gain controlled by a gain control signal and wherein the gain of each channel is a known function of a plurality of constants of corresponding to each amplifier and of the gain control signal, can be calibrated by the following method. The method comprising the steps of measuring each output of each amplifier at a corresponding plurality of gain control values and at a corresponding input to each amplifier. The number of the plurality of the constants equals the number of the plurality of the gain control values. The method continues by computing the gain of each amplifier at the step of measuring. The constants corresponding to each amplifier are then computed according to the function and computed gain. A corresponding changed gain control signal is applied to each amplifier according to the function to set the corresponding gain of each amplifier to a corresponding predetermined calibrated value.

Abstract: The low-frequency integrated amplifier comprises a voltage amplifier stage and two power amplifier stages including power amplifier means driven by the voltage amplifier stage and fedback by means of a respective feedback network dimensioned so that, at the frequency at which the phase shift of the power stages exceeds 180.degree., the open loop gain thereof is less than 0 dB, so as to prevent, for any kind of load and for every output voltage, any oscillation of said stages, and ensure the absolute stability of the system.

Abstract: A power MOSFET linear amplifier includes a plurality of paralleled MOSFETS having a gate-to-source resistor to ensure simultaneous turn-on and sharing of the load current. An arc lamp is connected in series with a 400 volt power supply and a variable ballast element in the form of the power MOSFET linear amplifier. The linear amplifier includes four similar modules. Each module is a hybrid circuit constructed with eight MOSFETs connected in parallel. Each MOSFET includes a similar gate-to-source resistor in addition to an appropriate gate resistor and source resistor. Under operating load current conditions, the gate-to-source resistors are laser trimmed to establish precise equalized current sharing in response to the specified operating input voltages. The module is set with the gate voltage slightly above the operating threshold voltage range of the MOSFET.

Abstract: A composite amplifier includes a plurality of signal amplifiers. The amplified signals are coupled by transmission lines to node points for combination. In order to achieve a reduction in power below full output power, some of the amplifiers are deenergized. Shorting switches at selected points along the transmission lines are selectively rendered conductive to adjust the impedances to maintain impedance match. Short- or open-circuited transmission lines may also be switched in-circuit to aid in maintaining impedance match.

Abstract: An arrangement for combining the output signals from a plurality of transmission units (2, 3) tuned to the same frequency and included in the arrangement, while each arrangement is by itself capable of functioning as a transmission unit (2) whose output signal can be combined with that of another transmission unit (3). For each pair of transmission units (2, 3) to be combined the arrangement incorporates control circuitry (5) for generating a control signal used to effect combination of the output signals of the pair of transmission units (2, 3) in phase. The control circuitry (5) includes a sum and difference network (6) connected to the transmission units (2, 3) and a detector (7), for example a phase-sensitive detector, for deriving the control signal from the output signals of the sum and difference network (6), the sign of the control signal being of special importance.

Abstract: Two or more distributed amplifiers are paralleled to increase the available output power. Phase shifters are coupled to the amplifiers as necessary to maximize output power at a frequency. With this phase adjustment, the amplifiers may have effective electrical lengths which differ one from another by N (360.degree.), where N is zero or an integer. Values of N other than zero undesirably reduce the instantaneous bandwidth of the paralleled amplifiers. The bandwidth is maximized by the addition of sufficient delays to reduce N to zero.

Abstract: A bank of differential amplifier circuits includes specialized circuits to provide multi-channel differencing with a minimum number of active devices such that the differences between pairs of analog input signals, such as available from patient monitoring electrodes, are derived with half the number of active devices normally utilized. In one embodiment, two operational amplifier circuits are used in a differencing channel which functions together to provide differencing, a properly delayed input signal for use in another differencing channel, high input impedance buffering, a low impedance output for each differential amplifier channel, time-coincident, matched outputs for each differential amplifier channel, and with an additional operational amplifier, a DC rejection circuit which does not affect the low output impedance or the differencing function, thereby to eliminate the necessity of providing separate buffers and active delay circuits which can result in the use of twice the number of active devices.

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: A four-way power splitter/combiner apparatus comprises five unbalanced ports, configured as a common port and four other ports, with power introduced into the common port, over a relative wide frequency band, being substantially equally divided between the four other ports, and vice versa. Each of the first and second ports of each pair of the four other ports has a substantially in-phase signal thereat, with the first in-phase pair of ports having a substantially 180.degree. signal phase difference from the substantially in-phase signals at the other pair of ports. Each of the balun and 2-to-1 transformers of the push-pull 4-port apparatus can be fabricated of a magnetically-decoupled coaxial cable assembly, wherein the cables are all of the same characteristic impedance as the load impedance magnitude at each of the five ports.

Abstract: A variable power amplifier having a constant current differential amplifier driving a cascaded driving amplifier, a variable power amplifier including a vacuum tube for selectively amplifying output signals wherein the drive of the variable power amplifier is determined by the plate shunt resistive loading of the vacuum tube, a push-pull amplifier including an output transformer operatively coupled to the variable power amplifier and to an amplifier output terminal to amplify and apply to the amplifier output terminal a selectively amplified output signal, and a variable damping circuit including a sensing element for sensing the loading on the output tranformer and a circuit for defining a feedback loop for producing a feedback signal having magnitude and polarity which are determined by the sensing element and wherein the variable damping circuit includes a circuit for applying the feedback signal as an input to the constant current differential amplifier to control the current level thereof as a function o

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 feed forward microwave power amplifier having a divider for dividing an input signal into two parts, a first main amplifier for amplifying one of the divided signals, means for providing a part of the output of the first amplifier as a signal S.sub.1, means for providing a signal S.sub.2 by another output of the divider, a subtractor for providing the difference between S.sub.2 and S.sub.1, a second amplifier having the same gain as that of the first amplifier for amplifying this difference, a 3 dB coupler for coupling an output S.sub.4 of the first amplifier and an output S.sub.4 e, where e is a constant, of the second amplifier to provide coupled power which is free from distortion, and adjusting means for adjusting the level of signals S.sub.1 and S.sub.2 so that S.sub.2 is higher than S.sub.1, and the value e is in the range between 0.2 and 0.5.

Abstract: A first multi-port hybrid coupler is formed by n2.sup.n-1 (where n is an integer equal to or greater than 2) hybrid couplers alone, which are divided into n stages, each including 2.sup.n-1 hybrid couplers. A signal input to any one of N (=2.sup.n) input terminals of the first stage is distributed equally to N output terminals of the nth stage. The N output terminals of the nth stage of the first multi-port hybrid coupler are connected to N amplifiers at the input side thereof, respectively, and the N amplifiers are connected at the output side to a second multi-port hybrid coupler. The second multi-port hybrid coupler is identical in construction with the first multi-port hybrid coupler, but its input terminals and output terminals are reverse from those of the latter and the input terminals of the second multi-port hybrid coupler are connected to the N amplifiers in an order reverse from the order of arrangement of the output terminals of the first multi-port hybrid coupler.

Abstract: An equalization circuit with switched capacitor filters, each having variable filter characteristics, that is adapted to provide power equalization on digital transmission lines that are subject to power losses for high frequency signals. The power equalization is provided automatically by switching in or out of a filter one or more of its capacitors in response to detected variations in line power levels. Identical filters are connected in parallel and alternatively applied within the equalizer circuit, the capacitor switching occurring only in a filter circuit that is not actively applied within the equalizer circuit.

Abstract: A power amplifier having plural parallel amplification circuits of different gains selectively actuable to zero and maximum gains, and electronic switches to select a circuit for connection to a common output junction.

Abstract: An amplifier switchable between a dual-channel amplifier and a BTL amplifier includes first and second amplifying circuits having a non-inverting input, an inverting input and an output, a first input terminal receiving a first input signal and applying it to the non-inverting input of the first amplifying circuit, a second input terminal receiving a second input signal, a first switch selectively applying a signal to the non-inverting input of the first or second amplifying circuit, a second switch controlling the application of an output from the first amplifying circuit to the inverting input of the second amplifying circuit, a controlling circuit controlling the first and second switches, first through third loads and a third switch controlling the application of an output from the first and second amplifying circuits to the first and second loads, respectively, or to the respective ends of the third load.

Abstract: An electronic amplifying apparatus intended for sound reproduction and for music instrument amplification wherein two parallel amplifiers, working simultaneously, each in a different class of operation, are fed from a single driver or signal source and whose outputs are combined. In the preferred embodiment at least two pairs of push-pull vacuum tubes are required and they are arranged so that one pair operates Triode Class A while the other pair (or pairs) operates Pentode Class AB (or Class B). The circuit can then be optimized so that the desirable sonic characteristics of Class A Triode operation are imparted into the Class AB (or Class B) Pentodes which actually produce all or nearly all of the power. The output power waveform has the high power and efficiency typical of Class AB (or Class B) Pentode operation but without the detrimental sonic side effects, namely, there is the complete absence of crossover or "notch" distortion, and there is a "soft" gradual onset of clip.

Abstract: A balance control circuit for controlling the difference in volume between right and left audio stereo signals. DC output voltages of an amplifier provided in a preceding stage to the balance volume control circuit are utilized as bias voltages for amplifiers provided in the rear stage of the balance control circuit, and the sliding contacts of variable resistors are grounded through a single capacitor, with the result that the manufacturing cost of the circuit is reduced.

Abstract: A phase modulation circuit to provide at an output terminal an output signal controllably shifted from 0.degree. to 360.degree. relative to an input signal provided at an input terminal includes a first 90.degree. coupler connected between the input terminal and second and third 90.degree. couplers, four gain controllable amplifiers, fourth and fifth 90.degree. couplers and an in phase combiner with its output connected to the output terminal. Two of the amplifiers are connected between the second and fourth couplers. The additional amplifiers are connected between the third and fifth couplers. The fourth and fifth couplers are connected to the inputs of the in-phase combiner. The gain through the various amplifiers is adjusted to control the amount of phase shift through the circuit.

Abstract: An electronic amplifying apparatus intended for sound reproduction and for music instrument amplification wherein two parallel amplifiers, working simultaneously, each in a different class of operation, are fed from a single driver or signal source and whose outputs are combined. In the preferred embodiment at least two pairs of push-pull vacuum tubes are required and they are arranged so that one pair operates Triode Class A while the other pair (or pairs) operates Pentode Class AB (or Class B). The circuit can then be optimized so that the desirable sonic characteristics of Class A Triode operation are imparted into the Class AB (or Class B) Pentodes which actually produce all or nearly all of the power. The output power waveform has the high power and efficiency typical of Class AB (or Class B) Pentode operation but without the detrimental sonic side effects, namely, there is the complete absence of crossover or "notch" distortion, and there is a "soft" gradual onset of clip.

Abstract: The signal to be amplified is applied to a quadrature coupler which splits the signal equally to provide two output signals in phase quadrature. The quadrature signals are amplified equally, which generates a second harmonic in each of the signals 180 degrees out of phase. The amplified signals are combined in an in-phase power divider to provide a single amplified output signal wherein the out-of-phase second harmonic signals cancel.

Abstract: Method of removing distortions in amplifiers which includes forming a difference between a part of an input voltage and of an output voltage of an amplifier so that only the distortions remain, amplifying the difference voltage by means of another amplifier to a value equal to that of the distortion part in the output of the first-mentioned amplifier and then combining the output voltage of both amplifiers so that distortions in the sum voltage are mutually compensated, including supplying a given input power to a first amplifier and twice the given input power to a phase equalization element, the first amplifier delivering output power with distortions, coupling out part of the output power via a coupling branch having directional waveguide couplers and feeding the output power part, with like amplitude though opposite phase, via a phase shifter element as well as a damping element, while opening a blocking diode, to a branch formed of the phase equalization element and an auxiliary amplifier, taking part of

Abstract: A radio-frequency switch of planar construction for connecting N input signals to M output signals in a broadcast switch mode or a matrix switch mode. The switch includes a single substrate or circuit board (49) and M output switches (50) disposed in a row on one face of the board, each output switch having N input ports. In the broadcast mode, there are N rows of distributed power dividers (such as 60, 62, 64 and 66), each row providing M outputs from a single input port, the outputs being connected by conductors (such as 90) to the output switches (50). The conductors effecting these cross-connections are formed for the most part on the reverse face of the circuit board, to avoid intersection between the cross-connections and the distributed power dividers. In the matrix mode, the power dividers are replaced by switches (110).

Abstract: An amplifier switchable between a dual-channel amplifier and a BTL amplifier includes first and second amplifying circuits having a non-inverting input, an inverting input and an output, a first input terminal receiving a first input signal and applying it to the non-inverting input of the first amplifying circuit, a second input terminal receiving a second input signal, a first switch selectively applying a signal to the non-inverting input of the first or second amplifying circuit, a second switch controlling the application of an output from the first amplifying circuit to the inverting input of the second amplifying circuit, a controlling circuit controlling the first and second switches, first through third loads and a third switch controlling the application of an output from the first and second amplifying circuits to the first and second loads, respectively, or to the respective ends of the third load.

Abstract: A quadrature combiner circuit is provided which employs a quadrature coupler to split an input radio frequency signal into split radio frequency signals which are amplified by respective amplifiers and recombined in a second quadrature coupler in such a manner as to minimize intermodulation distortion products. A feedback loop is employed to assure that the split amplified radio frequency signals incident upon the second quadrature combiner are maintained in quadrature relationship to assure intermodulation product cancellation.

Abstract: A method of amplifying an analog low-frequency signal, and a switching amplifier implementing the method, wherein the maximum amplifiable voltage of the analog input signal is divided up into as many voltage bands as there are switching stages provided in the switching amplifier, and one switching stage is associated with each voltage band. Thereby the number of switching stages actuated and their switched-on period may be modulated in dependence upon the amplitude. In this way it is possible to reduce considerably the total number of switching processes during one period of the low-frequency input signal and the losses connected with each switching process.

Abstract: An apparatus for driving n transducer units (n>1), each comprising one or more electro-acoustic transducers, comprises m signal inputs (m.gtoreq.1) for connecting m signal sources to the apparatus. Each signal input is connected to an associated amplifier unit and there are n signal outputs to which said transducer units may be connected. A signal input is connectable to one or more of the signal outputs via the associated amplifier unit. The apparatus further comprises k auxiliary amplifier units (k.gtoreq.1) with one or more of said auxiliary amplifier units being connectable in parallel with an arbitrary amplifier unit so that the total power of the apparatus may be reduced substantially.

Abstract: A parallel channel microwave amplifier comprising a plurality of amplificon channels interconnecting a power-dividing matrix and a power-combining matrix. Each amplification channel includes a phase shifter, an attenuator and a power amplifier connected in series. The device functions as a combination of amplifier and an r.f. attenuator/modulator.

Abstract: A feed forward circuit that can be used as an isolator or filter includes a first and a second directional coupler that, depending on the application, either splits an applied signal into two paths or combines the two paths to obtain an output signal. One path includes an electronically tunable band reject filter (or notch filter) which may be bypassed by a switch in the isolator application, and an inverting amplifier. The second path includes a delay line that compensates for the time delay of the signal in the first path due to the time delay of the inverting amplifier and electronically tunable band reject filter.

Abstract: A transient noise free type amplifier circuit includes a first amplifier having a noninverting input to which an input signal is applied, and a first output. An inverter inverts the input signal and supplies the inverted signal to a second amplifier having a signal input to which the inverted signal is applied, and a second output, and which second amplifier provides the same amplification as the first amplifier. A bias circuit supplies a predetermined bias potential to bias inputs of the first and second amplifiers, and a resistor circuit supplies the bias potential to the signal input of each of the inverter and the first amplifier. An output siganl which corresponds to the potential difference between the first output of the first amplifier and the second output of the second amplifier, is thus provided.

Abstract: A corporate amplifier is defined as and includes a plurality of N amplifier modules where N is a positive integer that is greater than one. The plurality of amplifier modules are driven by a power splitter which takes a signal that is to be amplified and divides it into N equal amplitude components. Each component is applied to a member of the plurality of N amplifier modules for amplification. The outputs of the power amplifier modules are combined by a power combiner that has N input terminals with each input terminal being connected to an output terminal of a member of the plurality of N amplifier modules. A fault detector detects failure of one or more of the plurality of N amplifier modules and provides a fault signal indicating thereby a failed amplifier module. A compensation circuit compensates both the power splitter and the power combiner means so that if a fault is detected in one or more of the plurality of N amplifier modules the performance of the corporate amplifier will be optimized.

Abstract: Circuitry is provided for simulating a combination of vacuum tube clipping and soft cross-over characteristics in a transistor power amplifier circuit. A first circuit includes a biasing network for assuring that the transistor amplifier saturates in response to high level input signals. A second circuit includes a biasing network for providing sufficient bias current to maintain the transistor in an active, rather than cutoff, operating region when the first circuit fails to provide the needed bias at times when the instantaneous input signal level is low but average or peak input levels are high. A combining circuit provides the higher of the bias values to the amplifier, to assure that the amplifier saturates for particular high level inputs yet operates at a modified, linear mode for low level inputs, thus simulating a compression characteristic of vacuum tube amplifiers.

Abstract: To obtain optimal operational sensitivity from an amplifier connected to a source of electrical signals, a technique utilizes multiple amplifiers connected together. The technique determines the number, N, of amplifiers (31 or 51) to be used and whether they should be connected in parallel (FIG. 3) or series (FIG. 5) in order to optimize the sensitivity of a given type of amplifier. Accordingly, multiple interconnection of amplifiers may be used in lieu of noise matching with transformers to minimize the excess-noise figure of the multiple amplifier circuit. The technique capitalizes on the advances in integrated circuit amplifier design, such as compactness and wideband performance, while providing lower loss and higher reliability through redundancy.

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 pulse width modulation amplifier in which interchannel distortion is eliminated by making the pulse transition times different between different ones of the channels. Ramp carrier signals having different phases are applied to respective pulse width modulation comparators of the two channels. The ramp carrier signals are generated by applying the output of an oscillator directly to one of the pulse width modulation comparators while the other is generated through a phase delay circuit which provides constant phase relationship independent of the frequency of the output of the oscillator. The output of the oscillator is coupled to one input of a comparator which produces first and second output signals one of which is in a high state depending upon the relative potentials of the two inputs to the comparator. The outputs are coupled to respective constant current sources which charge and discharge a capacitor in accordance with the output state of the comparator.

Abstract: An M by N switch matrix includes N input switches each single-pole M-throw, M output switches each N-throw single-pole with the N*M outputs of the N input switches coupled directly to respective ones of the N*M inputs of the M output switches whereby a signal applied at any of the N input switches can be coupled to the output of any one of the M output switches. The switches may consist of a plurality of dual-gate field effect transistors enabling the switching matrix to be utilized at microwave frequencies.

Abstract: An adjustable phase shifter for adjustably providing a 360.degree. range of phase shift to RF signals by dividing the RF signals into three equal parts, adjusting the relative amplitudes of the parts of the RF signals and combining the three parts of the RF signals at relative phase angles of 0.degree., 120.degree. and 240.degree..