Abstract: A low-noise preamplifier with an electronic amplifying element having an input (2) and an output (4), and with a first transformer (6) having a primary winding (5) and a secondary winding (8) is characterized in that the input (2) of the electronic amplifying element is the base of a transistor, the gate (G) of a field effect transistor (FET) or the grid of a vacuum tube, and the output (4) of the electronic amplifying element is the collector, the drain (D) or the anode, the output current (Ip) being passed from the electronic amplifying element through the primary winding (5) of the first transformer (6) to the output (7) of the preamplifier, wherein the secondary winding (8) of the first transformer (6) is connected to the input (2) of the electronic amplifying element. This preamplifier can be operated with extremely low noise and at any input impedance, in particular, at 50 ohms or 75 ohms.

Abstract: A method and apparatus provides an input structure for a power amplifier. In one example, the input structure has an input network and a predriver circuit to provide an input signal to the power amplifier. The input network includes a transformer for helping to maintain a constant input impedance. The predriver includes a limiting amplifier that provides isolation between the power amplifier and the RF input. A DC feedback circuit is used by the predriver that maintains the DC level of the inverters to a desired level.

Abstract: Methods and apparatus contemplate: an output transformer having at least first and second separate primary windings and at least one secondary winding, each winding including a first (in phase) end and a second (out of phase) end; at least first and second active elements, each having at least a pair of power terminals and a control terminal, one power terminal of each active element being coupled to a common node; and a switching circuit operable to change a circuit configuration of the first and second primary windings and the active elements between a class A mode and a class A/B mode.

Abstract: An isolated direct-current to direct-current (DC-to-DC) converter and associated method are provided which employ a class-D amplifier. An alternating current (AC) input voltage and a DC input voltage drive the class-D amplifier to produce an AC primary voltage. The AC primary voltage then drives a primary winding of a transformer, thereby generating an AC secondary voltage at a secondary winding of the transformer. The AC secondary voltage then drives a rectifier, yielding a rectified voltage. A low-pass filter is then accepts the rectified voltage to produce a DC output voltage.

Abstract: An RF amplifier system having improved power supply is presented and which includes a plurality of power amplifiers each having an output circuit for connecting a DC voltage source to one of a plurality of primary windings located on a first transformer. The first transformer has a plurality of secondary windings located thereon with each being a single turn secondary winding. The secondary windings are connected together in series. A second transformer is located in a cascaded arrangement with the first transformer and has a like plurality of single turn primary windings connected together in series and a like plurality of secondary windings are on said second transformer with each being connected to a rectifier for providing a controlled DC voltage.

Abstract: The invention provides a power amplifier system including a plurality of amplifiers, a plurality of primary transformer windings, a single secondary transformer winding. Each of the plurality of amplifiers includes a differential input that is commonly coupled to a system input port, and each the plurality of amplifiers also includes a differential output. Each of the plurality of primary transformer windings is coupled to the differential output of one of the plurality of amplifiers. The single secondary transformer winding is inductively coupled to all of the primary transformer windings and provides a system output port to which a load may be coupled.

Abstract: Circuits and methods for use in amplifying amplitude and phase modulated signals. A circuit uses a combiner with dual parallel signal amplifiers feeding it. The signal amplifiers have a low output impedance while the combiner does not provide any isolation between its inputs from the signal amplifiers. As in other Chireix architectures, the signals from the signal amplifiers are phase modulated prior to being fed to the combiner. The combiner then combines these two signals and, depending on how these two signals are combined, the resulting output of the combiner is amplitude modulated. The signal amplifiers may be Class D or Class F amplifiers to provide high efficiency amplification of the signals.

Abstract: A transformer of power-amplifier module for an audio device includes a casing having a first plug and a second plug formed thereon. In the casing, there is an amplifying circuit having an input electrically connected to the first plug and an output electrically connected to the second plug of the casing. The amplifying circuit terminates in a transformer at the output. Furthermore, the transformer is adjustable so as to control the amplitude of output voltage of the transformer of power-amplifier module.

Abstract: An amplifier comprising a transformer and a plurality of FETs, for example, three FETs. An input terminal, which receives a signal from an FM antenna, is connected to one end of the primary winding of the transformer. A power-supply voltage is applied to one end of the secondary winding of the transformer. A given middle part of the secondary winding is connected to an output terminal. The transistors have their source connected in parallel to the other end of the primary winding of the transformer, their drains connected in parallel to the other end of the secondary winding, and their gates connected to the ground.

Abstract: An integrated RF power amplifier 20 includes an on-chip input transformer (24) and an on-chip output transformer (28). Each of the transformers (24, 28) is formed from four spirals. Each primary winding (34, 42) and each secondary winding (38, 44) includes positive and negative spirals arranged so that positive current rotates in opposing rotational directions in the positive and negative spirals. The secondary winding (38) of the input transformer (24) and the primary winding (42) of the output transformer (28) each has a center tap (48, 50) located at the electrical and physical center of the winding. Positive and negative amplifiers (26) couple between the secondary winding of the input transformer (24) and the primary winding of the output transformer (28). DC biasing for the amplifiers (26) is provided through the positive and negative spirals of the center-tapped windings (38, 42) from the respective center taps (48, 50).

Abstract: A synthetic impedance line driver for driving a telecommunication line includes a complementary operational amplifier pair having cross-coupled positive feedback summing resistors. The driver circuit is configured to provide a relatively large multiplication of the values of relatively small valued output resistors to realize a synthesized impedance matching that of the driven line. A cross-coupled resistor network may be employed to cancel out far end signal components present in an analog canceler drive signal. The values of the auxiliary network resistors are ratioed such that the signal at nodes between resistors of branches of the network is a fraction of the open circuit voltage swing of the amplifiers, with far end signal components canceled.

Abstract: Apparatus and method are presented for use in disconnecting and/or replacing one of a plurality of M power amplifier modules in an RF transmitter while the transmitter is operating. Each amplifier module has first and second outputs that normally are connected across an associated one of M transformer primary windings. Also, M transformer secondary windings are provided with each associated with one of the primary windings. The secondary windings are connected together in series across a load. Each amplifier module has a control input for receiving a disable signal that disables the amplifier module. The apparatus for use in disconnecting and/or replacing includes a switch having a disable condition and an enable condition. A controller responds to the switch being in a disable condition for providing a disable signal.

Abstract: An inventive FET balun transformer uses a positive power supply alone, not a negative one, thus downsizing a device including the balun transformer. In the FET balun transformer, a voltage supplied from the positive power supply is divided by a voltage divider consisting of a pair of resistors. The gate of a first FET is biased at a positive voltage, which is obtained by getting the divided supply voltage further divided by a first resistor. The gate of a second FET is grounded with an AC grounded capacitor interposed therebetween and biased at a positive voltage, which is obtained by getting the divided supply voltage further divided by a second resistor. Thus, the gate and source of a third FET do not have to be set at a negative potential, but may be grounded directly and via a biasing resistor, respectively.

Abstract: A lossless feedback transistor amplifier circuit is described, including an input terminal and an output terminal, for the purpose of amplifying a signal voltage. The amplifier circuit also includes an augmentation circuit, connected from the emitter to the base of a common-base amplifying transistor, which detects an error voltage at the common-base transistor emitter, amplifies and inverts the error voltage, and then applies the amplified error voltage to the base of the common-base amplifying transistor, for the purpose of reducing the emitter error voltage and thus reducing the harmonic and intermodulation distortion of the lossless feedback amplifier. According to a further embodiment, a second transistor is used for amplifying the emitter error voltage. In a further embodiment, an inverting positive feedback amplifier is used for amplifying the emitter error voltage. In a further embodiment, a transformer is used to amplify and invert the emitter error voltage.

Abstract: A plurality of amplifiers are connected in cascade to form an in-line predistortion circuit. The amplifiers are unbalanced in that each amplifier stage in the circuit has two DC voltage rails which are independently controlled to provide different, i.e. offset, DC voltage levels to the unbalanced amplifiers. This unbalance in the amplifiers generates predistortion in a signal which can be used to cancel the inherent distortion caused by a non-linear device which subsequently processes or transmits the predistorted signal. Control of the DC voltage offset in at least one of the amplifier stages is necessary to match the predistortion to the inherent distortion being corrected. A tilt circuit can be used in cascade with the plurality of amplifiers (in front of the RF amplifiers) to compensate the amplitude change caused by the unbalanced RF amplifiers. Either side of the DC voltage can be changed in order to correct for either sublinear or superlinear laser diode curves.

Abstract: An electronic device, for example a signal receiver mounted on a vehicle for opening and closing the doors of the vehicle in response to telecontrol signals from a remote source, includes an intermediate frequency amplifier. The intermediate frequency amplifier comprises two amplifier stages arranged in cascade with respect to the input signal, with the biasing terminals of the two stages being connected in series across the supply. The arrangement gives much reduced current consumption.

Abstract: A high-efficiency amplifier (10, 18) that may be used in, for example, a radar system to amplify signals received at an exciter (22) before they are applied to an antenna (20). The amplifier includes, among other components, an adaptive matching network (48) that is controlled by a processing system (26) to allow the amplifier to be adaptively matched to the load as the operating frequency of the system undergoes changes. Specifically, the network is adjusted based upon information regarding the ratio R of reflected power over incident power measured at the load the last time the system operated at the same frequency. As a result, the system is able to respond more quickly to frequency changes.

Abstract: A circuit for combining first and second signals having the same frequency. The signals have a relative phase shift, 2a(t). The circuit generates a signal that is proportional to the sum or difference of signals. The circuit appears to be a resistive load; however, the circuit can be constructed from purely reactive circuit elements, and hence, does not dissipate energy. In one embodiment, the circuit is constructed from a transformer and two LC circuits in which the capacitance is varied in response to a(t). The circuit may be used to construct a high efficiency RF amplification stage.

Abstract: An isolation amplifier employs feedback to accurately amplify an input signal while maintaining electrical isolation between the input and output signals. The isolation amplifier consists of an amplitude modulator, an isolation transformer having a pair of matched secondary windings, a peak-detector output circuit, and a matching peak-detector feedback circuit. The isolation transformer couples an amplitude-modulated signal to both peak detector circuits while maintaining electrical isolation. The output from the feedback circuit is fed back to the amplitude modulator, so that the amplitude-modulated signal represents the difference between the input to the amplifier and the feedback signal.

Abstract: This optical receiver is capable of receiving broadband R-F modulated signals transmitted over fiber-optic cable. The receiver comprises a photodiode impedance matched to the input of an low noise, low distortion amplifier by an impedance matching transformer. A passive tuning network is placed between the photodiode and the transformer to improve the high frequency performance of the receiver. Distortion of the optical receiver is further reduced by cancelling even power distortion products from out of phase signals generated by the photodiode.

Abstract: An electronic switching arrangement is shown to consist of an effective balanced pi configuration using series and shunt FETs and transformer coupling so that the impedances seen by such FETs are optimized.

Abstract: A transconductance amplifier for emitting an output current that is a replica of a input voltage has its accuracy enhanced by a current comparator having a first magnetic core, a second magnetic core, a pair of ratio windings electromagnetically coupled with both the cores, and a detection winding electromagnetically coupled with the first core but not with the second core. A first of the ratio windings is connected in series with the output current of the transconductance amplifier. A high value resistor is connected in series with the second of the ratio windings across the input voltage of the transconductance amplifier whereby the current in the second ratio winding accurately reproduces the waveform of the input voltage. A further amplifier has its input connected to the detection winding. The output of this amplifier is so connected as to add a correcting current to the output current of the transconductance amplifier and thus provide the necessary accuracy enhancement.

Abstract: An input transformer circuit in which transformer-isolated, balanced inputs are provided operates with low distortion and employs a transformer that has an equal number of turns in the primary and secondary windings and which is operated in the current mode to drive the two inputs of an operational amplifier. One input of the operational amplifier is connected to ground and the circuit operates to drive the other input to virtual ground, so that by transformer action the signal voltage across the ends of the primary winding is essentially zero. Because the signal voltages across the primary and secondary windings of the transformer are both substantially zero, there is relatively no induced electromotive force and no signal distortion occurs in the transformer.

Abstract: Disclosed is a cascode amplifier circuit with improved current gain, linearity, overload performance and bandwidth which uses a step-down (of voltage) transformer between a driver stage and an output stage. One end of the primary of the transformer is connected to a driver transistor's collector and the other end is connected to the collector of a grounded-base output transistor. The transformer secondary is connected across the base and emitter of the output transistor. The transformer windings are phased such that a large driver current is forced through a high impedance, i.e. the primary winding impedance which is a multiple of the common base input impedance of the output transistor, resulting in power gain. The amplifier is capable of high maximum overloaded power output free of "break-up" of the waveform compared with conventional cascode operation, as well as greater power gain.

Abstract: A signal isolator including a coupling transformer with modulate/demodulate switches in series with the primary and secondary windings. The switches are driven in synchronism by an oscillator. Resonating capacitors are connected in parallel with the transformer windings and tuned to the switch operating frequency to control the flux in the transformer core. A transformer turns-ratio of less than unity introduces a corresponding attenuation, and a following amplifier counteracts that attenuation to produce an output signal at the original level. A return current resistor is connected between the output signal and the transformer secondary to produce a back-flow of current towards the transformer. This current provides for supplying the losses of the coupling circuit in a symmetrical fashion, both from the isolator input and its output, to reduce significantly variations in performance resulting from changes in ambient temperature.

Abstract: An improved input system for isolating resolver or synchro outputs from inputs to demodulators or analog-to-digital converters uses current transformers rather than voltage transformers. The resistances of resistors connected in series with the primary windings of the isolation transformers are adjusted to standardize the input currents of the transformers.

Abstract: A current branching circuit for an amplifier for first and second input terminals and a current supply feed terminal comprising a pair of magnetically coupled windings with one of the windings connected between the center conductor of a coaxial feed line and one of the input terminals and the other windings connected between the other input terminals to a capacitor which has its other side connected to the outer conductor of the coaxial line and wherein the pair of leads connecting the pair of windings to the pair of input terminals cross one another. The outer conductor of the coaxial line is connected to the current supply feed terminal through a second capacitor.

Abstract: A transformer-coupled isolation amplifier which can accept signals over a wide dynamic range while maintaining very high linearity. An input signal is applied to an input winding of a transformer. The secondary winding of the isolation transformer is connected across the differential inputs of a high-gain amplifier. Negative feedback is provided around the amplifier so that the transformer secondary winding is connected across a virtual short; and the negative feedback tends to drive the voltage applied to the inputs of the amplifier to a very small value. The negative feedback from the amplifier induces a current in the transformer secondary which cancels the flux produced by current flowing in the primary, thereby reducing the effects of non-linearities in the BH curve of the transformer.

Abstract: An electric amplifier useful for instance in simulators for strong electric signals, comprising several partial amplifiers so connected and voltage fed that they will amplify an interval each of the input voltage. Every partial amplifier comprises at least one amplification component and two gates, of which gates one is blocking those potentials applied to the component that are less than a given first value but is open for potentials exceeding said value while the other gate is open for potentials less than a given second value greater than said first value but is blocking the component for potentials exceeding said second value.

Abstract: An intermediate amplifier arrangement for communication lines in which the intermediate amplifier is divided into at least two partial amplifiers each having a capacitance between the outer conductor of the coaxial transmission line and the amplifier and connected to feed supply voltages such that the amplifiers are uncoupled from each other as to high frequency and utilizing low inductance and low resonance capacitors so as to obtain very low power consumption and large cyclical attenuation.

Abstract: There is disclosed an isolation amplifier having an input amplifier, an output amplifier, a transformer having primary and secondary windings, an alternator connected to the secondary winding of the transformer for alternately presenting a voltage and a high impedance to the secondary winding, a first switching device connected between the primary winding of the transformer and the output of the input amplifier for connecting the output of the input amplifier to the primary winding when the alternator presents a high impedance to the secondary winding and for disconnecting the output of the input amplifier from the primary winding when the alternator presents a voltage to the secondary winding and a second switching device connected between the secondary winding and the input to the output amplifier therefore connecting the input of the output amplifier to the secondary winding when the alternator presents a high impedance to the secondary winding and disconnecting the input of the output amplifier from the s

Abstract: A circuit arrangement for the ungrounded transmission of signals through testing points in communication systems with the aid of high-frequency oscillations. The high-frequency oscillations are controlled on the one side of the testing point and are rectified on the other side of the testing point. The rectified signals are utilized to reproduce the signals again. A resonant circuit is adjusted to the high-frequency oscillations and is galvanically separately coupled to a high-frequency generator. The resonant circuit is also connected to a modulation circuit and to the input of the testing point. The resonant circuit is coupled inductively to a demodulation circuit which forms the output of the testing point.

Abstract: An R. F. wide band amplifier is disclosed. It comprises a high impedance step up transformer at the input end, a wide band high impedance J-Fet attenuator connected to the step up transformer, a dual gate MosFet amplifier connected to the attenuator and a high impedance wide band step down transformer connected to the output of the MosFet. The output of the amplifier is taken from the stepped down side of the transformer.

Abstract: An input amplifier stage is isolated from the main body of an amplifier and instrument ground by a single transformer which provides both an energy path to the input stage and an amplifier signal path from the input stage using a modulated load technique. The secondary of the transformer, which is connected across the input amplifier, includes a rectifier and filtering components to provide a floating D. C. voltage supply.

Abstract: An isolator circuit of the type designed to accept an input current and to generate a corresponding output current which is isolated from the input. The isolator circuit is formed with a core developing a flux in response to the input current and having a feedback winding for carrying the isolated output current. A magneto-sensitive element, such as a Hall effect element, responds to flux in the core, and an amplifier receives the output of the magneto-sensitive element and supplies a current to the feedback winding so as to cancel the flux produced in the core due to the input current. Improved frequency response is attained by means of a compensation winding disposed to respond to the difference between the flux produced by the input current and the flux produced by the output current.