Abstract: This application relates to Class D amplifier circuits. A modulator controls a Class D output stage based on a modulator input signal (Dm) to generate an output signal (Vout) which is representative of an input signal (Din). An error block, which may comprise an ADC, generates an error signal (?) from the output signal and the input signal. In various embodiments the extent to which the error signal (?) contributes to the modulator input signal (Dm) is variable based on an indication of the amplitude of the input signal (Din). The error signal may be received at a first input of a signal selector block. The input signal may be received at a second input of the signal selector block. The signal selector block may be operable in first and second modes of operation, wherein in the first mode the modulator input signal is based at least in part on the error signal; and in the second mode the modulator input signal is based on the digital input signal and is independent of the error signal.

Abstract: A modular headphone system that can afford the wearer configurable choices of hearing protection and quality sound delivery for music and programming is provided. In an embodiment, a modular headphone includes a headband and an earpiece mounted to the headband. The earpiece comprises a can comprising a speaker, the can secured to the headband. A removable and replaceable music ear cup is removably mountable to the can to overlie the speaker. A removable and replaceable hearing protection/sound amplification (HP/amp) ear cup is removably mountable to the can to overlie the speaker.

Abstract: A sensor device which is suitable for receiving and transmitting signals and can be placed on a test person's head, includes a sensor device housing having a signal pin on its distal side for receiving a signal and a connection on its proximal side for the signal transmission of a signal received by the signal pin. A sensor device holder has an axial through opening in which the sensor device housing is disposed so as to be steplessly axially displaceable. When the sensor device housing is axially displaced relative to the sensor device holder, the sensor device housing does not change its radial orientation. A cap having a plurality of sensor devices is also provided.

Abstract: The present invention provides a mattress for measuring physiological parameters of a heart, comprising a mattress body, a first electrode, a second electrode and an electromagnetic shield, wherein the first electrode and the second electrode are located on the upper surface of the mattress body and the first electrode and the second electrode have a space therebetween; at least a portion of the electromagnetic shield is located on the lower surface of the mattress body and is insulated from the first electrode and the second electrode. In the above mattress provided by the present invention, the first electrode and the second electrode are shielded from ambient electromagnetic radiation effectively. The electromagnetic shield, by blocking the electromagnetic wave propagation path, prevents the electrodes from being polluted by electromagnetic radiation, achieving more accurate measurement.

Abstract: A transformer has first and second transformer windings including multiple differential ports. Each of the first and second transformer windings include a first transformer half-winding coupled to a first differential port of the differential ports. Each of the first and second transformer windings also include a second transformer half-winding coupled to a second differential port of the differential ports. Each of the first and second transformer windings is divided symmetrically at a common node to form the respective first and second transformer half-windings. The first transformer half-winding is configured to form one half of an inductance in each of the first and second transformer windings. The second transformer half-winding is configured to form another half of the inductance in each of the first and second transformer windings. The common node of the first transformer winding is configured to receive a supply voltage.

Abstract: An oscillator circuit comprises a push-push oscillator and a differential output, comprising a first and a second output circuit. The push-push oscillator has a first and a second branch. Each of the first and second branch comprises an own voltage divider branch of a common bridge circuit. Each of the first and second voltage divider branches comprises an own pair of micro-strip lines connected in series. Each of the first and second voltage divider branches has an own tap. Both taps are connected to each other by at least one of a first capacity and a micro-strip line. The differential output comprises a first and a second output terminal. The first output terminal is connected via the first output circuit to a first node. The second output terminal is connected via the second output circuit to a second node. Each of the first and second nodes of the push-push oscillator is a common node of both of the first and the second branches.

Abstract: The present disclosure relates to coupled circuits and methods of coupling circuits having a power supply wherein a plurality of transistors are inductively coupled directly to the power supply for providing a single DC supply voltage directly to each of the plurality of transistors, and wherein a plurality of transformers have primary and secondary windings, the primary and secondary windings providing, at least in part, inductive loads for inductively coupling the plurality of transistors to the power supply, the plurality of transformers also providing an AC signal path for coupling neighboring ones of the plurality of transistors together.

Abstract: An improvement in a buffer for driving a signal onto a power line is described. The buffer includes a second order filter. With the improvement, the collector-to-emitter potential of an emitter follower is maintained constant to substantially reduce the distortion associated with base-collector capacitance.

Abstract: An audio amplifier (100) switches between a pulsewidth-modulated (PWM) mode to an analog mode when required in order to reduce unwanted EMI when the signals being reproduced fall within a predetermined threshold range such as when reproducing low amplitude signals. Amplifier (100) includes both a pulsewidth-modulator (114) and a low-level analog amplifier (126) coupled to a speaker bridge circuit. When controller (106) determines that the input signal (102) is at a predetermined level, controller (106) selectively applies to the load (164) an analog signal instead of the PWM signal, this provides for improved dynamic range and reduced amplifier produced EMI.

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