A multi-level class D audio power amplifier for supplying an N-level drive signal to a loudspeaker. The multi-level class D audio power amplifier includes a switching matrix having controllable semiconductor switches where the switching matrix include at least (N−2) switch inputs, coupled to respective ones of (N−2) DC input voltage nodes, and at least 2*(N−2) switch outputs coupled to respective ones of 2*(N−2) intermediate nodes of a first output driver. A control circuit is configured to sequentially connect each of the (N−2) DC input voltages to a predetermined set of nodes of the 2*(N−2) intermediate nodes of the first output driver via the switching matrix in accordance with one or more of the 2*(N−1) modulated control signals of the first output driver. N is a positive integer larger than or equal to 3.

A power supply system for a plasma process includes two separate power supplies of essentially identical performance characteristics, including a first power supply and a second power supply, and a data transfer connection operably coupling the two power supplies for data communication between the two power supplies. The first power supply is configured to: receive, in a standby mode, data via the data transfer connection from the second power supply supplying power to a plasma process in a normal operating mode, and supply, in an active backup mode, power to the plasma process in place of the second power supply, as a function of the received data. The first power supply can supply in the active backup mode to the plasma process the power having one or more characteristics that are substantially the same as those of the power provided by the second power supply in the normal operating mode.

An apparatus includes an RF power amplifier with a controller and an impedance matching network. The RF power amplifier is configured to drive a load in electrical communication with the RF power amplifier. The impedance matching network is located electrically between the RF power amplifier and the load. The impedance matching network is configured to match an output impedance of the RF power amplifier and an impedance of the load. The impedance matching network includes a set of fixed value impedance matching circuits configured to provide different discrete values. The RF amplifier includes a variable DC power supply powering RF transistors to result in a variable output impedance for the amplifier. The controller selects an impedance matching circuit of the capacitor presets and/or the right setting for the variable DC supply that result in minimum reflected power to match the output impedance of the amplifier to the output load impedance.

A driver interface for a switch-based circuit includes an AC coupling capacitor, a first diode or a first series of diodes, and a second diode or a second series of diodes connected in series with the first diode or first series of diodes but with an opposing polarity. The AC coupling capacitor removes a DC voltage from an input bi-level drive signal that does not have the appropriate high and low drive levels needed to switch a FET in the switch-based circuit between fully ON and fully OFF states. The first diode or first series of diodes and the second diode or second series of diodes clamp the resulting AC-coupled drive signal to produce an output bi-level drive signal having the high and low drive levels needed to switch the FET between fully ON and fully OFF states. The driver interface maintains the high and low drive levels of the output bi-level drive signal irrespective of any changes made to the duty cycle or pulse density of the input bi-level drive signal.

Disclosed are advances in the arts with novel and useful electronic circuitry with pop and click noise reduction. A load circuit is connected with a full or single-ended half-H bridge circuit and another circuit mechanism in a configuration by which a signal may be used to selectably bring the load circuit terminals to a selected voltage level when an externally applied signal is not present.

An audio signal modulation and amplification circuit includes a common-mode electric potential controller, a carrier generator, and channel circuits. The common-mode electric potential controller is configured to generate one or more first common-mode electric potentials and second common-mode electric potentials. The carrier generator is adapted to receive the first common-mode electric potential to generate a carrier signal. Each of the channel circuits includes a filter, a comparison circuit, and a driving circuit. The filter is adapted to filter an input signal and generate a filtered signal based on a corresponding one of the second common-mode electric potentials. The comparison circuit is configured to compare the potential of the carrier signal with the potential of the filtered signal to generate a pulse-width modulation signal. The driving circuit is configured to be turned on or off in response to the pulse-width modulation signal to output a load driving signal.

A switching system is connected to the power amplifier of an RF system. The switching system can switch the DC supply voltage to the power amplifier while handling the high DC current and the nanosecond switching speed requirements that are mandatory for most RF systems. The embodiments can rapidly control DC voltages but not interfere with the optimized operation of the RF transistor. The embodiments provide a desired sharp turn-on leading edge for an RF pulse while eliminating the extremely long and undesirable ramp down that typically occurs beyond the desired RF pulse period.

A method and apparatus of load detection for an audio amplifier system is described. A load detector includes a first load terminal and a second load terminal; a controller coupled to the first and second load terminals and configured to in a first control loop, vary a first current supplied to a first load terminal dependent on the difference between a first reference signal and the detected first load terminal voltage; and in a second control loop, vary a second current supplied to the second load terminal dependent on the difference between a second reference signal and the detected second load terminal voltage; and to determine a current through a load connected between the first load terminal and the second load terminal from the second current value, and a voltage across the load from the detected voltage difference between the first load terminal voltage and the second load terminal voltage.

[OBJECT] To provide a radio-frequency power source capable of outputting radio-frequency power having a desired waveform changing at high speed.

[SOLUTION] A radio-frequency power source 1 includes two DC-RF converting circuits 4A, 4B and an RF combining circuit 5 for combining the outputs from both DC-RF converting circuits 4A, 4B. The DC-RF converting circuits 4A, 4B amplify radio-frequency voltages v.sub.a, v.sub.b inputted from a radio-frequency signal generating circuit 8, and output radio-frequency voltages v.sub.PA, v.sub.PB. The RF combining circuit 5 outputs radio-frequency voltage v.sub.PX at a ratio corresponding to the phase difference θ between the radio-frequency voltages v.sub.PA and v.sub.PB. A controlling circuit 9 switches the phase difference θ between θ1 and θ2. As a result, the power P.sub.X outputted from the RF combining circuit 5 becomes pulsed radio-frequency power having a high level period and a low level period. Since the switching of the phase difference θ can be performed at high speed, it is possible to output pulsed radio-frequency power with a high switching frequency between the first level and the second level.

According to one embodiment, a class-D amplifier including: a PWM modulator that outputs a PWM modulation signal in response to an input signal; and a drive circuit that amplifies the PWM modulation signal, and supplies it to an output end. The drive circuit includes: a first output transistor whose main current path is connected between a power source supplying end and the output end; a second output transistor having a size larger than a size of the first output transistor; and a resistance element that is connected between the main current path of the first output transistor and the output end.