According to one embodiment, a compact low-power receiver comprises first and second analog circuits connected by a digitally controlled interface circuit. The first analog circuit has a first direct-current (DC) offset and a first common mode voltage at an output, and the second analog circuit has a second DC offset and a second common mode voltage at an input. The digitally controlled interface circuit connects the output to the input, and is configured to match the first and second DC offsets and to match the first and second common mode voltages. In one embodiment, the first analog circuit is a variable gain control transimpedance amplifier (TIA) implemented using a current mode buffer, the second analog circuit is a second-order adjustable low-pass filter, whereby a three-pole adjustable low-pass filter in the compact low-power receiver is effectively produced.

A unique electrical system includes a first electrical component and a second electrical component. A conductor electrically couples the first electrical component with the second electrical component. A sensor is constructed to sense an AC power flow in the conductor and output an AC signal proportional to the AC power flow. A band-pass filter is in electrical communication with the sensor and constructed to receive and filter the AC signal and to generate an AC voltage proportional on the AC signal. A controller is in electrical communication with the band-pass filter, and is operative to receive and sample the AC voltage. The controller is configured to execute program instructions to sum sequential AC voltage values received from the band-pass filter over a sample time period, and to determine whether an arc fault has occurred based on the summed AC voltage values.

According to one embodiment, in a complex band pass filter, a second input signal to be supplied to a second active filter circuit has a substantially 90 degree phase difference from a first input signal to be supplied to a first active filter circuit. The first feedback circuit includes a first element having a first impedance and feeds back an output signal of the first active filter circuit to input side of the second active filter circuit. The second feedback circuit includes a second element having a second impedance different from the first impedance and feeds back an output signal of the second active filter circuit to input side of the first active filter circuit. The output circuit outputs an output signal according to a signal from the first active filter circuit and to a signal from the second active filter circuit.

A programmable band-pass filter circuit, which is included by an analog front-end circuit and used for capacitance detection, includes an operational amplifier, an input resistor, a feedback resistor, and a feedback capacitor. The operational amplifier includes a first input coupled to a reference level, a second input, and an output. The input resistor has a first end coupled to a sensed capacitor and a second end coupled to the second input of the operational amplifier. The feedback resistor and feedback capacitor are connected between the second input of the operational amplifier and the output of the operational amplifier, respectively.

Provided is an active filter device capable of effectively reducing common mode noise and differential mode noise and optimizing filter characteristics. The active filter device includes an inverting amplifier circuit 37 that inverts and amplifies a common mode voltage and a differential amplifier circuit 64 that differentially amplifies a differential mode voltage, and an output voltage of the inverting amplifier circuit 37 is applied as a common mode compensation voltage to Y capacitors 21, 22, an output of the differential amplifier circuit 64 obtained by amplifying a voltage of a positive-side power supply line 11 is applied as a differential mode compensation voltage to a negative-side X capacitor 42, and an output of the differential amplifier circuit 64 obtained by amplifying a voltage of a negative-side power supply line 12 is applied as a differential mode compensation voltage to a positive-side X capacitor 41.

The floating immittance emulator is presented in four embodiments in which four new topologies for emulating floating immittance functions are detailed. Each circuit uses three current-feedback operational-amplifiers (CFOAs) and three passive elements. The present topologies can emulate lossless and lossy floating inductances; capacitance, resistance, and inductance multipliers; and frequency-dependent positive and negative resistances.

A baseline restorer circuit including a controller; a sample control circuit arranged to receive an input voltage signal that is output from a circuit stage comprising an amplifier, and configured to capture a sample of the input voltage signal at a sampling time in response to receiving a control signal from the controller; an analogue processing stage to receive the sample and a constant baseline reference voltage and selectively process the sample to provide an output voltage; a transconductance stage to convert the output voltage to a compensation current and supply the compensation current to an input of the circuit stage; and a change detector to monitor if the input voltage signal changes during a time interval around the sampling time, and if no change is detected in the input voltage signal during the time interval, the controller is configured to control the analogue processing stage to process the sample.

The present disclosure provides an audio amplifying circuit and a playing device, including: N-order filters and an integrated circuit; after an original audio signal passes through the N-order filters, a filtered signal is obtained; after the filtered signal passes through the integrated circuit, a corresponding digital signal is output; where the number of operational amplifiers adopted in the N-order filters is smaller than N, and N is a natural number greater than 1.

Provided is an active filter device capable of effectively reducing common mode noise and differential mode noise and optimizing filter characteristics. The active filter device includes an inverting amplifier circuit 37 that inverts and amplifies a common mode voltage and a differential amplifier circuit 64 that differentially amplifies a differential mode voltage, and an output voltage of the inverting amplifier circuit 37 is applied as a common mode compensation voltage to Y capacitors 21, 22, an output of the differential amplifier circuit 64 obtained by amplifying a voltage of a positive-side power supply line 11 is applied as a differential mode compensation voltage to a negative-side X capacitor 42, and an output of the differential amplifier circuit 64 obtained by amplifying a voltage of a negative-side power supply line 12 is applied as a differential mode compensation voltage to a positive-side X capacitor 41.

Described embodiments include an apparatus with a first amplifier having first inputs and first outputs. A second amplifier has second inputs and a second output. A first chopper circuit is coupled between third inputs and the first inputs. A second chopper circuit is coupled between the first outputs and the second inputs. A balanced filter is coupled to the second inputs.