Abstract: An apparatus for testing components for use in a power system includes at least one power amplifier circuit configured to be coupled to the component and a control circuit configured to operate the power amplifier circuit responsive to at least one state of a component emulator for the component included in a system emulator for the power system. The component emulator may include at least one power electronics converter circuit and the control circuit may be configured to control at least one of a voltage and a current of the at least one power amplifier circuit responsive to at least one of a voltage and a current of the at least one power electronics converter circuit. The control circuit may be further configured to control the component emulator responsive to at least one state of the at least one power amplifier circuit.

Abstract: A device provides path data associated with a network that includes network devices interconnected by links. The path data includes data identifying a first path and a second path to be provided through the network. The device provides an instruction to cause the network devices to provide information identifying the first path and to route traffic via the first path, and receives an indication of a failure associated with the first path. The indication causes the network devices to provide information identifying the second path and to re-route the traffic from the first path to the second path. The device causes the failure associated with the first path to be repaired while the traffic is re-routed to the second path, and provides, based on causing the failure to be repaired, another instruction to cause the network devices to route the traffic via the first path.

Abstract: An air-conditioning system includes an outside air conditioning device, an air conditioning device, and a machine learning apparatus, and includes a state variable acquiring unit configured to acquire state variables, a learning unit configured to perform learning by associating the state variables with at least either an operating capacity of the outside air conditioning device or an operating capacity of the air conditioning device, and a reward calculating unit configured to calculate a reward that correlates with a total of energy consumption of the outside air conditioning device and energy consumption of the air conditioning device. The learning unit performs the learning by using the reward calculated in a period determined in accordance with a time duration until the total of the energy consumption changes after at least either the operating capacity of the outside air conditioning device or the operating capacity of the air conditioning device has changed.

Abstract: A power amplifier can include a carrier amplifier having first and second differential amplification cells with outputs coupled by a primary loop of a carrier transformer, and a peaking amplifier having first and second differential amplification cells with outputs coupled by a primary loop of a peaking transformer. The power amplifier can further include a combiner having a quarter-wave circuit implemented between the secondary loop of the carrier transformer and a secondary loop of the peaking transformer. The quarter-wave circuit can be configured to provide a characteristic impedance, such that the carrier and peaking amplifiers are presented with an impedance that is approximately the same as the characteristic impedance when both of the carrier and peaking amplifiers are turned on, and the carrier amplifier is presented with an impedance that is approximately twice the characteristic impedance when the carrier amplifier is turned on and the peaking amplifier is turned off.

Abstract: An electric power conversion device supplies electric power of a DC power source from an input part to an output part through a power conversion circuit having a transformer and switches. The transformer has primary and secondary coils magnetically connected. The device has a choke coil, an auxiliary coil and a control part. The auxiliary coil is connected to the output part and magnetically connected to the choke coil. The auxiliary coil is wound to allow a current to flow from a negative-electrode side to a positive-electrode side of the output part when a current flows from the power source to the choke coil. The control part performs a switching control of the switches to supply electric power of the source to the output part through the auxiliary coil to prevent generation of magnetic flux in the primary coil and the current from flowing in the secondary coil.

Abstract: Methods, apparatus, and systems for distributing network loads in a manner that is resilient to system topology changes. Distribution functions and associated operations are implemented on multiple load splitters such that if a load splitter becomes inoperative, another or other load splitters can forward packets corresponding to flows previously handled by the inoperative load splitter without requiring flow state synchronization to be maintained across load splitters. The distribution functions are implemented in a manner that distributes packets for the same flows to the same servers through system topology changes, addressing both situations when servers fail and/or are taken off-line and when such servers or replacement servers are brought back on-line. The techniques are facilitated, in part, via use of redistributed flow lists and/or Bloom filters that are marked to track redistributed flows. A novel Bloom filter recycle scheme is also disclosed.

Abstract: Transformer-based Doherty power amplifier (PA). In some embodiments, a Doherty PA can include a carrier amplification path having an output that includes a carrier transformer, and a peaking amplification path having an output that includes a peaking transformer. The Doherty PA can further include a combiner configured to combine the outputs of the carrier and peaking amplification paths into an output node. The combiner can include a quarter-wave circuit implemented between the carrier and peaking transformers.

Abstract: Various examples are directed to analog vacuum tube emulator circuits. In various examples, a vacuum tube emulator circuit may comprise a first circuit and a second circuit. The first circuit may be effective to receive, a first voltage, a second voltage, and a third voltage. The first circuit may be effective to develop, at an input of the first circuit, a first current based on the first voltage, the second voltage, and the third voltage. The first circuit may output the first current to an output node. The second circuit may be effective to receive the first voltage, the second voltage, and the third voltage. The second circuit may be effective to develop, at an input of the second circuit, a second current based on the first voltage, the second voltage, and the third voltage. The second circuit may output the second current to the output node.

Abstract: An optical communication device and an optical communication method are provided. The optical communication device includes a laser source, an optical amplifier, and an optical signal generating chip. The laser source generates a laser beam. The optical amplifier is coupled to the laser source and amplifies light intensity of the laser beam in a specific wavelength band. The optical signal generating chip includes a micro-resonator and a modulation module. The micro-resonator is coupled to the optical amplifier and generates a multi-wavelength frequency comb according to the amplified laser beam. The modulation module is coupled to the micro-resonator and modulates a communication signal set to generate a plurality of optical modulated signals according to the multi-wavelength frequency comb.

Abstract: An apparatus for outputting an audio signal with improved sound quality is provided. The apparatus includes a modulation and amplification unit for pulse modulation and switching amplification of an input audio signal and generating an amplified signal which corresponds to the input audio signal; and a vacuum tube amplification unit for inputting a vacuum tube signal generated by attenuating the amplified signal and adding harmonics of a vacuum tube to the amplified signal, to the modulation and amplification unit to provide a mellow sound.

Abstract: An audio signal output apparatus includes a modulation signal generator for generating a first modulation signal by pulse-modulating an input audio signal of one channel using a first carrier signal or a first sampling clock, which has a first frequency; a vacuum tube filter unit comprising a vacuum tube and for generating a vacuum tube signal by allowing the first modulation signal to pass through the vacuum tube; a frequency modulation unit for generating a second modulation signal by pulse-modulating the vacuum tube signal; and a power switching amplifier for outputting an amplification signal corresponding to the second modulation signal.

Abstract: The present invention allows amplification with low distortion and high efficiency. A power amplifier of the present invention comprises signal conversion means which generates a digital signal and an analog signal from an input signal that is an amplification target based on a signal generation parameter, a switching amplifier which amplifies the digital signal, a linear amplifier which amplifies the analog signal, and DC level detection means which detect a DC level of at least one of the signal amplified by the linear amplifier and the amplified signal and output a detection result to the signal conversion means, wherein the signal conversion means adjust the signal generation parameter so that the DC level inputted by the DC level detection means is virtually equal to zero.

Abstract: Methods are provided for solid-state implementation of a vacuum tube replacement device (VTRD) that includes a communication interface. The communication interface enables the VTRD to command or retrieve information regarding VTRD performance, function, and status. A VTRD may communicate with other VTRDs in a target amplifier retrofitted with compatible VTRDs and to an external user interface for programming or query/response. The methods presented for the vacuum tube replacement device system(s) are equally useful for non-vacuum tube systems such as audio amplifier circuits.

Abstract: An apparatus and method for amplifying a transmission signals in multiple modes and multiple bands. The apparatus includes a tunable power amplifying module adapted to receive a plurality of signal types comprising multiple modes and multiple bands. The tunable power amplifying module includes a first and second power amplifier stages and a number of tunable matching networks configured to optimize an impedance value based on the mode and band of the signal to be amplified.

Abstract: An amplifier circuit includes a transconductance amplifier at an input side of the amplifier circuit, a transimpedance amplifier connected to an output of the transconductance amplifier, and a voltage amplifier connected to an output of the transimpedance amplifier. The transconductance amplifier and the transimpedance amplifier form a low-impedance node at an interface thereof. A feedback circuit is connected between an output of the voltage amplifier and the low-impedance node between the transconductance amplifier and the transimpedance amplifier. The transconductance amplifier, the transimpedance amplifier, and the voltage amplifier form a main amplifier stage. The feedback circuit senses an imbalance in an output of the main amplifier stage, whereby a correction signal is integrated and negatively fed back to the low-impedance node between the transconductance amplifier and the transimpedance amplifier.

Abstract: A power amplifier is provided with an AD converter pulse modulating an envelope signal extracted from a high frequency modulation signal; a switching amplifier amplifying an output signal from the AD converter; a low-pass filter removing high frequency noise from an output signal from the switching amplifier; a voltage control device controlling a power supply voltage of the switching amplifier; and a high frequency amplifier amplifying a phase-modulated signal having a constant envelope and having output from the low-pass filter as a power supply. The average power of the envelope signal to be inputted to the AD converter is permitted to be constant so that an input dynamic range of the AD converter can be most efficiently used. In addition the average power of the output signal from the power amplifier is adjusted by a power supply voltage to be supplied to the switching amplifier.

Abstract: An output circuit of a vacuum-tube amplifier is disclosed. An output circuit of a conventional vacuum-tube amplifier has shortcomings that a front end amplification unit uses a coupling condenser or a transformer to output an AC signal to an output node, a bias voltage of a cathode of a vacuum tube is varied in response to an input signal in an output buffer and, when the bias voltage is higher than a voltage set by a bias resistor, signal attenuation by the difference between the bias voltage and the set voltage is generated. To solve these shortcomings, the output circuit of the vacuum-tube amplifier includes a front end amplification unit for amplifying an input signal using a vacuum tube and an output amplification unit for power-amplifying the output signal of the front end amplification unit using a vacuum tube.

Abstract: An output circuit of a vacuum-tube amplifier is disclosed. An output circuit of a conventional vacuum-tube amplifier has shortcomings that a front end amplification unit uses a coupling condenser or a transformer to output an AC signal to an output node, a bias voltage of a cathode of a vacuum tube is varied in response to an input signal in an output buffer and, when the bias voltage is higher than a voltage set by a bias resistor, signal attenuation by the difference between the bias voltage and the set voltage is generated. To solve these shortcomings, the output circuit of the vacuum-tube amplifier includes a front end amplification unit for amplifying an input signal using a vacuum tube and an output amplification unit for power-amplifying the output signal of the front end amplification unit using a vacuum tube.

Abstract: Methods are provided for solid-state implementation of a vacuum tube replacement device that supplements the functional performance of the target replacement device, i.e., a traditional glass vacuum tube. Example functions may include OEM or user adjustable parameters such as gain and/or frequency response (e.g. transfer function), current and/or voltage saturation thresholds, bias condition, input and/or output impedance, linear-to-non-linear transfer function(s) (e.g. soft clipping parameters), power dissipation, communication protocols, and audio/visual indication parameters such as signal limiting detection, safety, stress, or wear-out conditions, and tube emulation model type to name a few. The methods presented for the vacuum tube replacement device system(s) are equally useful for non-vacuum tube systems such as audio amplifier circuits.

Abstract: A system is provided for a solid-state implementation of a vacuum tube replacement device. The system may derive power from a target amplifier filament supply. The system may include active or passive functions for noise reduction, voltage isolation, servo biasing, and other functions. The vacuum tube replacement device is pin-for-pin compatible with standard vacuum tube circuit pin configurations. The vacuum tube replacement device system architecture is equally useful for non-vacuum tube systems such as audio amplifier circuits.

Abstract: A system is provided for a solid-state implementation of a vacuum tube replacement device. The system may derive power from a target amplifier filament supply. The system may include active or passive functions for noise reduction, voltage isolation, servo biasing, and other functions. The vacuum tube replacement device is pin-for-pin compatible with standard vacuum tube circuit pin configurations. The vacuum tube replacement device system architecture is equally useful for non-vacuum tube systems such as audio amplifier circuits.

Abstract: An amplifier is described including a pair of cathode-coupled pentode vacuum tubes. A first pentode of the pair includes a control grid configured to receive an input signal. A second pentode of the pair includes a control grid configured to be coupled to an input reference signal. A cascaded voltage regulator includes a first stage configured to generate a plate reference voltage for providing voltage to a plate of each pentode. The regulator includes a second stage configured to generate a screen reference voltage based on the plate reference voltage for providing voltage to a screen grid of each pentode. The amplifier can also include a push-pull output stage having a servo circuit configured to adjust the control bias signal for one of a pair of vacuum tubes included in the stage until the plate currents in the pair of tubes are substantially equal.

Abstract: A DC offset cancellation circuit employs multiple feedback factors for canceling DC offset by increasing convergence time. The DC offset cancellation circuit features an active low-pass analogue filter including a variable resistor, an amplifier, a capacitor pair and a comparator, the amplifier being coupled to an output of the variable resistor. Negative feedback is provided from the output of the variable resistor to the input signal source, the capacitor pair is coupled to the amplifier, one input of the comparator is coupled to an output of the amplifier, and a second input of the comparator is coupled to a reference voltage source such that a comparison signal is output by the comparator to the variable resistor after comparing the negative feedback signal with a reference voltage.

Abstract: A hybrid preamplifier with a vacuum tube input stage driving a JFET output stage dubbed TIJO (for Tube Input JFET Output) that uses zero feedback circuitry and a common low voltage B+ power supply. A single output low voltage transformer provides all necessary voltages including the filament voltage. No attempt is made to minimize distortion or maximize bandwidth by adding feedback. The vacuum tube is mounted externally to allow easy tube swapping for varying the gain and tonal palette, with no dangerous high voltages present.

Abstract: A hybrid preamplifier with a vacuum tube input stage driving a JFET output stage dubbed TIJO (for Tube Input JFET Output) that uses zero feedback circuitry and a common low voltage B+ power supply. A single output low voltage transformer provides all necessary voltages including the filament voltage. No attempt is made to minimize distortion or maximize bandwidth by adding feedback. The vacuum tube is mounted externally to allow easy tube swapping for varying the gain and tonal palette, with no dangerous high voltages present.

Abstract: A RF amplification system which includes a RF modulation unit fed by an optical carrier and an RF input signal, the modulation unit modulating the RF input signal onto the optical carrier to produce a modulated RF optical signal; an array of optical amplifiers coupled to the modulation unit for receiving and amplifying the modulated RF optical signals; and a detecting unit having at least one photodetector coupled to the array of optical amplifiers for receiving and detecting the modulated RF optical signals, the at least one photodetector producing an amplified RF output in response thereto.

Abstract: An amplifier system including a vacuum tube amplifier having an input signal terminal, an output signal terminal, and an electron source, and a control circuit having an input terminal coupled to one of the input signal terminal and the output signal terminal, and for controlling a kinetic energy of electrons emitted by the electron source based on one of an input signal to the vacuum tube amplifier and an output signal from the vacuum tube amplifier. According to another embodiment, the control circuit may be for controlling an amount of electrons emitted by the electron source based on one of the input signal to the vacuum tube amplifier and the output signal from the vacuum tube amplifier.

Abstract: A musical amplifier that includes a vacuum tube and a transistor. The vacuum tube is connected to the gate of the transistor, so that the current flow through the transistor is controlled by the vacuum tube. According to one example of the invention, the vacuum tube-transistor arrangement is set up in a “push-pull” arrangement, where a vacuum tube-transistor combination controls positive voltages, and another vacuum tube-transistor combination controls the negative voltages delivered by the system, the system output being at approximately zero voltage when not under load. Also, the use of the “Edison effect,” referred to as “thermionic emission” from vacuum tubes to variably regulate output transistor bias current resulting in substantially reduced total harmonic distortion is also disclosed.

Abstract: An apparatus for generating an amplified effect in an asymmetrical hysteretic system is disclosed. The asymmetrical hysteretic system comprises a transponent, a bias that externally grades the transponent, an energy source that drives the transponent, and a small stimulus amplified by a gain factor of the transponent. A method for generating an amplified effect in an asymmetrical hysteretic system is also disclosed.

Abstract: A musical amplifier that includes a vacuum tube and a transistor. The vacuum tube is connected to the gate of the transistor, so that the current flow through the transistor is controlled by the vacuum tube. According to one example of the invention, the vacuum tube-transistor arrangement is set up in a “push-pull” arrangement, where a vacuum tube-transistor combination controls positive voltages, and another vacuum tube-transistor combination controls the negative voltages delivered by the system, the system output being at approximately zero voltage when not under load. Also, the use of the “Edison effect,” referred to as “thermionic emission” from vacuum tubes to variably regulate output transistor bias current resulting in substantially reduced total harmonic distortion is also disclosed.

Abstract: Dual amplifying circuits having a magnetic tunnel junction device and a field effect transistor configured in a complementing set are disclosed herein. In one embodiment, the field effect transistor is operable to control a current level of a current operating signal flowing through the magnetic tunnel junction device. In another embodiment, the magnetic tunnel junction device is operable to control a voltage level of a voltage signal being applied to a gate terminal of the field effect transistor. The gain-bandwidth product of both embodiments is greater than the individual gain-bandwidth products of the individual devices through the elimination of noise contributing resistive type circuit elements.

Abstract: The output signal converter for a tube amplifier includes semiconductor devices for amplifying or attenuating an output signal of the tube amplifier while maintaining the output properties of the tube amplifier. The output signal converter according to one embodiment has an output transformer (TR) having an input terminal (TRa); a first circuit branch (C1) connected between the input terminal (TRa) and an output terminal of the tube amplifier and a second circuit branch (C2) connected to the input terminal (TRa) of the output transformer (TR) and in parallel to the first circuit branch and including components that produce an electric current proportional to a current level in the first circuit branch. The first and second circuit branches are located between the tube amplifier and the output transformer (TR) and include semiconductor devices so that the output signal from the tube amplifier is amplified while maintaining the output properties of the tube amplifier.

Abstract: The output signal converter for a tube amplifier includes semiconductor devices for amplifying or attenuating an output signal of the tube amplifier while maintaining output properties of the tube amplifier. The output signal converter in preferred embodiments has an output transformer (1) connected to the tube amplifier, a current amplifier and a voltage amplifier serially connected with each other via a node, and a speaker (4). The current amplification factor (Ac) of the current amplifier (2) and the voltage amplification factor (Av) of the voltage amplifier (3) are related according to the following equation: Ac*Av=−k, wherein k is a constant.

Abstract: A hybrid thermionic valve and solid state audio amplifier. A complete tube amplifier is scaled to produce a relatively low power yet also retain its small and large signal distortion characteristics. The output of the scaled amplifier is amplified by a relatively linear solid state amplifier. In one embodiment of the invention, a plurality of tube amplifiers are coupled in parallel and input to a mixing circuit for selectably mixing the outputs of the tube amplifiers and providing the mixed outputs to the solid state amplifier.

Abstract: Methods, systems and computer program products for the reassignment of communications sessions to a primary network communications path from a secondary network communications path are provided, which detect the availability of the primary network communications path and reroute existing transferable communications sessions to the primary network communications path from the secondary network communications path. Non-transferable communications sessions are maintained over the secondary network communications path until such non-transferable communications sessions are terminated. Upon termination of all such non-transferable communications sessions, the secondary network communications path may be deactivated. Additionally, new communications sessions may be assigned to the primary network communications path if the availability of the primary network communications path has been detected.

Abstract: In a direct coupled type vacuum tube amplifying circuit, to stabilize the operation and simplify the feedback loop, a plate power source EB5 is connected to a plate of a vacuum tube V5 of a first stage through a constant current source 1. A grid of a vacuum tube V6 of a next stage is connected to the plate of the vacuum tube V5 through a first resistance R3. A second resistance R4 is connected between the grid and the cathode of the vacuum tube V6. A negative power source EC6 is connected to the resistance R4 through a constant current source 2. In this constitution, the grid bias voltage of the second vacuum tube V6 is defined by the voltage drop of the second resistance R4.

Abstract: An electronic amplifying apparatus for sound reproduction and musical instrument amplification including at least two pairs of power output devices which are independently switchable between triode and pentode operation. The amplifier further contains a switch apparatus to select the amount of negative feedback within the amplifier.

Abstract: In this hybrid amplifier circuit the vacuum tube is direct coupled or DC coupled to the output of a solid state amplifier in a cathode follower configuration. An automatically operative bypass component, such as a Zener diode, LED, transistor junction or relay, diverts the signal output of the solid state amplifier around the vacuum tube stage when bias conditions or other vacuum tube operating conditions signify that the vacuum tube is still warming up or for some reason inoperative. Thus the hybrid circuit produces amplification at full volume and at low distortion even while the vacuum tube is warming up. The vacuum tube provides a desirable warming coloration to the sound that may be user adjusted by controlling the level of closed loop feedback within the circuit. Lower total harmonic distortion is achieved in a pentode vacuum tube device by direct coupling the screen and control grids. Lower voltage use of power pentodes wired in nonconventional "triode mode" is achieved.

Abstract: A reflected plate amplifier (RPA) for use with electronic audio equipment. The RPA comprises an input circuit for receiving an input signal, a vacuum tube, a plate current reflector, and an output circuit for delivering an output signal. The vacuum tube has a control grid coupled to the input circuit for receiving the input signal, and a plate for delivering a plate current responsive to the input signal. The plate current reflector is a transistor having an input terminal coupled to the plate of the vacuum tube for receiving the plate current, and an output terminal for delivering a reflected current which is responsive to the plate current of the vacuum tube and therefore responsive to the input signal, while the plate current reflector holds the plate voltage of the vacuum tube substantially constant for a wide range of the plate current of the vacuum tube.

Abstract: The direct coupled solid state-vacuum tube hybrid circuit matches a high impedance audio source to a low impedance audio destination. The resulting device supplies essentially unit gain and has both single ended and balanced outputs. The solid state operational amplifier and vacuum tube devices are DC coupled and supplied from a common low voltage DC power supply. The vacuum tube is incorporated directly in the feedback loop of the operational amplifier and a suitably chosen dampening resistor allows the circuit to provide vacuum tube characteristic warming effects without unwanted distortion or tube microphonics.

Abstract: A high-performance, distortion-free, audio push-pull amplifier has a class A driver stage that drives a class B push-pull output stage that is coupled to a load through a transformer that has a center tap primary with screen taps. The driver tube cathodes are coupled to the output tube grids. The driver tube plates are tied to the screen taps on the output transformer primary. These taps are also coupled to the output tube screen grids. At low power levels the driver stage drives the load through the output transformer. As power level rises the power stage supplies more and more of the output power. This circuit avoids notch or crossover distortion at low power levels.

Abstract: A field emitting drain field effect transistor FEDFET device which combines the desirable frequency response and current control characteristics of a field effect transistor (or other transistor) with the higher voltage higher power level characteristics of a field emission triode vacuum tube device to provide characteristics improved over those of either component element. The combination device is physically as well as electrically integrated in a semiconductor like structure. Equivalent circuit and frequency response characteristics are disclosed.

Abstract: An audio power amplifier for general audio and sound reinforcement use, or musical amplification, stringed or otherwise, which combines the sonic properties of vacuum tube amplification with the modern technology of solid state electronics, with its attendant advantages.

Abstract: An improved transimpedance amplifier includes a common cathode-connected vacuum tube first stage, coupled to a common-drain-connected MOSFET second stage, and an optional common drain-connected MOSFET third stage. Preferably, capacitive feedback is coupled from the output of the second stage to the input of the vacuum tube stage, to control the transimpedance of the amplifier. The circuit takes advantages of the low stray inter-electrode capacitances, low delay and transit times of the vacuum tube and the high transconductance of the MOSFET second and optional third stages, in a way complementary to one another to form a high transimpedance amplifier whose characteristics are controlled almost exclusively by the feedback capacitance or other feedback impedance, rather than by gain and stray capacitance terms of individual devices. The resulting transimpedance amplifier is useful in a number of applications, for example, in audio preamplifiers and audio power amplifiers.

Abstract: The present invention is an audio frequency power amplifier input circuit having improved vacuum tube circuit topology. The improved circuit includes a direct current feedback circuit within the input circuitry which stabilizes the operating point of a phase inverter. The feedback circuit maintains optimum operation of the circuit despite variations in tube characteristics or supply voltages. Another aspect of the improved circuit comprises a low impedance phase inverter which improves the drive capability of the phase inverter to push-pull power output vacuum-tube grids.

Abstract: The present invention relates to a feedforward-error-correction amplifier system comprising a switching circuit, a linear-amplification means, and a summing network, wherein an amplifier-system input signal is connected to a first input port of the linear-amplification means, and an output voltage signal produced at an output port of the linear-amplification means is fed to a first input port of the summing network, a signal which is a function of a current flowing in the output port of the linear-amplification means is fed to an input port of said switching circuit, said switching circuit having an output port at which a switching output signal is produced and which switching output signal is fed to another input port of the summing network, an output current flowing in the output port of the switching circuit having a time rate of change limited by a low-pass-filter means, a sensing signal which is a function of the switching output signal being fed to another input port of the linear-amplification means, t

Abstract: A high-efficiency low-distortion parallel amplifier or regulator is driven by an input signal source V.sub.i. An input signal passes to a linear circuit LC, and the output current i.sub.1 from the linear circuit passes to the input of a switching circuit SC. Alternatively, the input to the switching circuit may be any other signal that is a function of the linear-circuit output current. The output of the switching circuit passes through a coupling network CN and is applied with the output current of the linear circuit to a load impedance ZL. The output of the switching circuit acts to reduce the output current of the linear circuit so that the power it supplies is low. A low linear-circuit output current is usually sufficient to drive the switching circuit and coupling network to the maximum current required by the load. The system automatically adjusts independently of the load impedence so that with high output current most of the current is supplied by the switching circuit.

Abstract: A power amplifier including a klystron is stabilized against variations in output power with a simplified servo-loop system and cooperating temperature compensation. The system is fully solid-state, digital, and includes an operator-presettable initial power selector, a power output sensor, comparator logic, variable attenuation responsive to error signals indicative of deviation from the preset power, and temperature compensation means, for assured accuracy and stability.

Abstract: An amplifier for a capacitive load which includes a pair of high-voltage tube output circuits connected in a power output tube arrangement operating in push-pull for driving a capacitive load together with a feedback network connected between the Schmitt arrangement and a pair of transistors interconnected in a complementary difference amplifier circuit, the output of the complementary difference amplifier circuit connected to the driving tube of the power output tube arrangement to provide an amplifier output level having low distortion, positive DC centering and a high order of stability.

Abstract: An audio amplifier including a non-inverting amplifier stage that provides linear amplification without loop feedback for low distortion audio systems. The amplifier stage includes a triode vacuum tube or a triode connected pentode vacuum tube and a P channel field effect transistor (FET). The vacuum tube and the FET are connected in a series combination in which the source of the FET is connected to the cathode of the tube through a suitable resistance. The drain of the FET is connected to a negative voltage and both the gate of the FET and the grid of the tube are at DC ground potential. The input signal to be amplified is fed into the gate of the FET and the output is taken from the plate of the tube which is supplied with a positive voltage through a suitable load. In most applications the grid of the tube is connected to ground, however in some applications the grid may serve as an extra inverting input.