In accordance with embodiments of the present disclosure, a method of driving a playback waveform to an electromagnetic actuator by a transducer driving system may include operating the transducer driving system in a first mode wherein the electromagnetic actuator is driven with the playback waveform in a closed loop to form a closed-loop voltage drive system that includes a negative impedance, operating the transducer driving system in a second mode wherein the electromechanical actuator is driven with the playback waveform in an open loop, and operating a mode switch for transitioning the transducer driving system to operate between the first mode and the second mode.

An apparatus for detecting difference in operating characteristics of a main circuit by using a replica circuit is presented. In one exemplary case, a sensed difference in operating characteristics of the two circuits is used to drive a tuning control loop to minimize the sensed difference. In another exemplary case, several replica circuits of the main circuit are used, where each is isolated from one or more operating variables that affect the operating characteristic of the main circuit. Each replica circuit can be used for sensing a different operating characteristic, or, two replica circuits can be combined to sense a same operating characteristic.

An audio device includes a network interface, an amplifier that amplifies an audio signal received through the network interface, and a processor configure to obtain an output value of a signal from the amplifier and sends the output value of the signal through the network interface.

A radio frequency amplifying device according to an embodiment includes load impedance calculating circuitry and controlling circuitry. The load impedance calculating circuitry is configured to calculate a load impedance on the basis of information about a voltage standing wave rate and a phase on an output side of radio frequency amplifying circuitry. The controlling circuitry is configured to adjust a gain and a phase of a signal to be input to the radio frequency amplifying circuitry, in accordance with the load impedance calculated by the load impedance calculating circuitry.

A power amplifier includes an over-current protection loop and/or an over-voltage protection loop to assist in preventing operation outside a safe operation zone. In a further exemplary aspect, triggering of the over-current protection loop adjusts a threshold voltage for the over-voltage protection loop. In further exemplary aspects, the over-current protection loop may adjust not only a bias regulator, but also provide an auxiliary control signal that further limits signals reaching the power amplifier. In still further exemplary aspects, the over-voltage protection loop may operate independently of the over-current protection current loop or the over-voltage protection loop contribute to an over-current protection signal.

An audio signal reproduction apparatus includes a temperature detection unit detecting a temperature of a battery pack, a voltage detection unit detecting a voltage of the battery pack, and a control unit performing an output control on a basis of temperature information detected by the temperature detection unit and voltage information detected by the voltage detection unit.

A system comprises a positive voltage supply node and a negative voltage supply node configured for connection to a load, a power source coupled between the positive voltage supply node and the negative voltage supply node, an energy storage device, a solid-state switch, and a control system. The energy storage device and the solid-state switch are connected in series between the positive voltage supply node and the negative voltage supply node. The control system is configured to control activation and deactivation of the solid-state switch to (i) allow the energy storage device to be discharged and supply power to a load, and to (ii) modulate an amount of charging current that flows through the energy storage device from the power source (or load) to recharge the energy storage device.

A system for testing a subject transistor with constant power. The system may include an amplifier, a measurement voltage source, and a exercise voltage source. The amplifier may have an output connected to a gate of the subject transistor. The amplifier may have a first input and a second input. The measurement voltage source may be connected to the first input of the amplifier for use in measuring characteristics of the subject transistor. The exercise voltage source may be connected to the first input of the amplifier for exercising the subject transistor. The second input of the amplifier may be connected to a source of the subject transistor through a resistor.

In certain aspects, a method is provided for measuring power using a resistive element coupled between a power amplifier and an antenna. The method includes squaring a voltage from a first terminal of the resistive element to obtain a first signal, squaring a voltage from a second terminal of the resistive element to obtain a second signal, and generating a measurement signal based on a difference between the first signal and the second signal. In some implementations, the resistive element is implemented with a power switch.

A transistor package according to one exemplary embodiment includes main transistors and a sub-transistor placed in the same package as the main transistors and having a smaller size than the main transistors. It is thereby possible to provide a transistor package with more versatility capable of forming various types of Doherty amplification circuits such as a Doherty amplification circuit with auto-biasing function and an extended Doherty amplification circuit with desired operating characteristics, an amplification circuit including the same, and a method of forming a transistor.