An acoustic apparatus includes a class-D amplifier including a current feedback circuit, and a speaker system including a voice coil driven by the class-D amplifier. The speaker system is configured such that, in a case where the speaker system is driven by an ordinary amplifier having a first output resistance lower than a second output impedance of the class-D amplifier, a Q factor of the speaker system falls below a predetermined lower limit of an ordinary Q factor range of an ordinary speaker system. The current feedback circuit is configured to increase the second output impedance of the class-D amplifier by feeding a current flowing to the voice coil back to an input of the class-D amplifier so as to increase a Q factor as the acoustic apparatus higher than the predetermined lower limit of the ordinary Q factor range and within the ordinary Q factor range.

The present disclosure provides a current detection circuit for a loudspeaker 500, comprising a first detection resistor RSP, a second detection resistor RSN, a sampling selection circuit 100, an input selection circuit 200, and a processing circuit 300. By adding the sampling selection circuit 100 and the input selection circuit 200, voltages on two ends of the corresponding detection resistors (RSP, RSN) are sampled according to the fact that potential differences of an output stage VOP and an output stage VON of a class-D audio power amplifier 400 are in different semi-periods, and the current of the loudspeaker 500 is obtained through processing, thereby detecting the current of the loudspeaker 500 without adding an anti-clipping distortion function to the class-D audio power amplifier 400.

The present disclosure provides a current detection circuit for a loudspeaker 500, comprising a first detection resistor RSP, a second detection resistor RSN, a sampling selection circuit 100, an input selection circuit 200, and a processing circuit 300. By adding the sampling selection circuit 100 and the input selection circuit 200, voltages on two ends of the corresponding detection resistors (RSP, RSN) are sampled according to the fact that potential differences of an output stage VOP and an output stage VON of a class-D audio power amplifier 400 are in different semi-periods, and the current of the loudspeaker 500 is obtained through processing, thereby detecting the current of the loudspeaker 500 without adding an anti-clipping distortion function to the class-D audio power amplifier 400.

An amplifier circuit acting as a line driver in a line between a central station and field devices connected thereto comprising: a DC/DC converter integrated in the circuit as a power stage comprising a DC/pulse converter with two electrically isolated switching stages; a logic block preceding the converter, generating control signals for the switches from a PWM signal and feeding them into the converter in an electrically isolated manner using drivers; a priority block generating the PWM signal; a first and a second controller. The priority block forwards output from the first or second controller. The first controller generates a fault signal based on a voltage limit and an output voltage fed back within the amplifier circuit via a feedback path. The second controller generates a fault signal based on a current limit and the output current. The central station defines the current limit and the voltage limit.

Embodiments of the present disclosure include a harmonic power amplifying circuit with high efficiency and high bandwidth and a radio-frequency power amplifier. The circuit comprises an input matching network (11), a transistor (M), and an output matching network (12); a gate of the transistor (M) connected to an output end of the input matching network (11), a drain thereof connected to an input end of the output matching network (12), and a source thereof being grounded; wherein the output matching network (12) enables a lower sideband of the harmonic power amplifying circuit to work in a continuous inverse F amplification mode and an upper sideband of the harmonic power amplifying circuit to work in a continuous F amplification mode; wherein the output matching network (12) and a parasitic network of the transistor (M) form a low pass filter. By transitioning from the continuous inverse F power amplifier working mode to the continuous F power amplifier working mode, the efficiency of a continuous harmonic control power amplifier is effectively improved to be higher than 60%, a relative bandwidth is improved to be higher than 80%, and the harmonic impedance is simple to match and easy to realize.

Embodiments of the present disclosure include a harmonic power amplifying circuit with high efficiency and high bandwidth and a radio-frequency power amplifier. The circuit comprises an input matching network (11), a transistor (M), and an output matching network (12); a gate of the transistor (M) connected to an output end of the input matching network (11), a drain thereof connected to an input end of the output matching network (12), and a source thereof being grounded; wherein the output matching network (12) enables a lower sideband of the harmonic power amplifying circuit to work in a continuous inverse F amplification mode and an upper sideband of the harmonic power amplifying circuit to work in a continuous F amplification mode; wherein the output matching network (12) and a parasitic network of the transistor (M) form a low pass filter. By transitioning from the continuous inverse F power amplifier working mode to the continuous F power amplifier working mode, the efficiency of a continuous harmonic control power amplifier is effectively improved to be higher than 60%, a relative bandwidth is improved to be higher than 80%, and the harmonic impedance is simple to match and easy to realize.

A photoelectric conversion apparatus includes a pixel which includes a photoelectric conversion element; a signal line connected with the pixel; a voltage-current conversion unit configured to convert a voltage signal of the signal line into current; and a conversion unit that includes an oversampling type analog-to-digital conversion circuit that converts the current outputted from the voltage-current conversion unit into digital signals. The voltage-current conversion unit converts the voltage signal of the signal line into the current without sampling and holding and outputs the converted current to the conversion unit.

A driving circuit of a loudspeaker includes a periodic signal generation circuit, a signal processing circuit, a class-D amplifier circuit, a current sensing circuit, and a sample and hold circuit. The periodic signal generation circuit is arranged to generate a periodic signal and a control signal. The signal processing circuit is coupled to the periodic signal generation circuit, and is arranged to generate a pre-driving signal. The class-D amplifier circuit is coupled to the signal processing circuit, and is arranged to drive the loudspeaker according to the pre-driving signal. The current sensing circuit is coupled to the class-D amplifier circuit, and is arranged to generate a current sensing signal. The sample and hold circuit is coupled to the periodic signal generation circuit and the current sensing circuit, and is arranged to sample and hold the current sensing signal according to the control signal, to generate a current sampling signal.

A driving circuit of a loudspeaker includes a periodic signal generation circuit, a signal processing circuit, a class-D amplifier circuit, a current sensing circuit, and a sample and hold circuit. The periodic signal generation circuit is arranged to generate a periodic signal and a control signal. The signal processing circuit is coupled to the periodic signal generation circuit, and is arranged to generate a pre-driving signal. The class-D amplifier circuit is coupled to the signal processing circuit, and is arranged to drive the loudspeaker according to the pre-driving signal. The current sensing circuit is coupled to the class-D amplifier circuit, and is arranged to generate a current sensing signal. The sample and hold circuit is coupled to the periodic signal generation circuit and the current sensing circuit, and is arranged to sample and hold the current sensing signal according to the control signal, to generate a current sampling signal.

A class-D amplifier with good signal-to-noise ratio (SNR) performance is shown. The class-D amplifier includes a loop filter, a pulse-width modulation signal generator, a gate driver, a power driver, and a feedback circuit, which are configured to establish a closed amplification loop. The feedback circuit is configured to establish a feedback path. The class-D amplifier further includes a feedback breaker. The feedback breaker breaks the feedback path in response to conditions in which there no-signal information in the class-D amplifier.