According to one embodiment, in a biquad filter, an output terminal of a first integrator is connected to an input terminal in a negative pole side of a second integrator, an output terminal of the first integrator is connected to a first input terminal in a negative pole side of an adder through the inversion amplifier, an output terminal of the second integrator is connected to a second input terminal in the negative pole side of the adder, an input terminal to which an input signal is input is connected to a third input terminal in the negative side of the adder, and an output terminal of the adder is connected to an input terminal in a negative pole side of the first integrator.

Examples of amplifiers and n.sup.th-order loop filters thereof are configured to enable fast and robust recovery from saturation, while limiting signal distortion at or near full power delivery across multiple process and temperature corners. An example n.sup.th-order loop filter comprises n series-coupled resistor-capacitor (RC) integrators. In an example, each of the second RC integrator to the (n−1).sup.th RC integrator has a reset mechanism responsive to a reset signal output from a reset controller when an input signal overload condition is detected at the input. Upon detecting the overload condition, each of the third RC integrator to the (n−1).sup.th RC integrator is hard reset, the n.sup.th RC integrator is not reset, and a controlled reset is performed on the second RC integrator to recover from saturation caused by the signal overload condition, while maintaining the output signal below the 1% total harmonic distortion (THD) level at or near full power delivery.

In an illustrative example, a device includes an operational amplifier of an active bandpass filter circuit. The device further includes an adjustable resistance device configured to adjust a center frequency associated with the active bandpass filter circuit. The device further includes an adjustable capacitance device configured to adjust the center frequency and a bandwidth associated with the active bandpass filter circuit.

According to one embodiment, in a biquad filter, an output terminal of a first integrator is connected to an input terminal in a negative pole side of a second integrator, an output terminal of the first integrator is connected to a first input terminal in a negative pole side of an adder through the inversion amplifier, an output terminal of the second integrator is connected to a second input terminal in the negative pole side of the adder, an input terminal to which an input signal is input is connected to a third input terminal in the negative side of the adder, and an output terminal of the adder is connected to an input terminal in a negative pole side of the first integrator.

A reconfigurable analog filter includes a transimpedance amplifier configured to convert a current signal into a voltage signal, an input capacitor configured to form a current-mode low pass filter together with an input impedance of the transimpedance amplifier, a variable load circuit including at least one switch configured to selectively close a circuit path to provide a resistor and/or a capacitor as a load of the transimpedance amplifier according to a control signal, and a low pass filter configured to filter the voltage signal.

A filter for motor speed measurement signals includes one or more resonators configured to filter signals having a frequency that is proportional by a predetermined factor to the frequency of the motor whose speed is measured.

A reconfigurable analog filter includes a transimpedance amplifier configured to convert a current signal into a voltage signal, an input capacitor configured to form a current-mode low pass filter together with an input impedance of the transimpedance amplifier, a variable load circuit including at least one switch configured to selectively close a circuit path to provide a resistor and/or a capacitor as a load of the transimpedance amplifier according to a control signal, and a low pass filter configured to filter the voltage signal.

The object is to simplify the configuration of a filter in a reception apparatus. The reception apparatus includes a filter. The filter provided in the reception apparatus selects a signal transmission characteristic that is one of a band stop characteristic or a low pass characteristic. Further, selection of the signal transmission characteristic in the filter provided in the reception apparatus is performed in response to a desired signal and an interference signal. In the filter provided in the reception apparatus, passage of the desired signal and attenuation of the interference signal based on the selected signal transmission characteristic are executed.

The object is to simplify the configuration of a filter in a reception apparatus. The reception apparatus includes a filter. The filter provided in the reception apparatus selects a signal transmission characteristic that is one of a band stop characteristic or a low pass characteristic. Further, selection of the signal transmission characteristic in the filter provided in the reception apparatus is performed in response to a desired signal and an interference signal. In the filter provided in the reception apparatus, passage of the desired signal and attenuation of the interference signal based on the selected signal transmission characteristic are executed.

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.