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.

Certain aspects of the present disclosure are generally directed to a tunable active filter and a method of calibrating a tunable active filter. One example apparatus is a filter circuit that generally includes a resistor-capacitor (RC) topology tunable active filter comprising a first amplifier, a second amplifier, and a feedback path coupled between an input of the first amplifier and an output of the second amplifier. The filter circuit also includes a negative transconductance circuit coupled to a first node of the tunable active filter.

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 single-chip tunable bandpass filter is provided having a bandpass filter circuit with all tuning components for the bandpass filter circuit formed on the single-chip to provide a programmed center frequency for the tunable bandpass filter. The bandpass filter circuit may include, but is not limited to, a plurality of serially coupled singe stage biquad filter circuits coupled to an input formed on the single-chip and configured to provide a bandpass filtered output signal to an output formed on the single-chip. The bandpass filtered output may be provided by an output buffer formed on the single-chip. The single-chip includes at least one tuning input to receive data for tuning stored in a data register formed on the single-chip. The data register provides control bits to the tuning components that include a programmable resistor responsive to the control bits to vary the programmable resistor to adjust programmed center frequency.

Certain aspects of the present disclosure are generally directed to a tunable active filter and a method of calibrating a tunable active filter. One example apparatus is a filter circuit that generally includes a resistor-capacitor (RC) topology tunable active filter comprising a first amplifier, a second amplifier, and a feedback path coupled between an input of the first amplifier and an output of the second amplifier. The filter circuit also includes a negative transconductance circuit coupled to a first node of the tunable active filter.

A single-chip tunable bandpass filter is provided having a bandpass filter circuit with all tuning components for the bandpass filter circuit formed on the single-chip to provide a programmed center frequency for the tunable bandpass filter. The bandpass filter circuit may include, but is not limited to, a plurality of serially coupled singe stage biquad filter circuits coupled to an input formed on the single-chip and configured to provide a bandpass filtered output signal to an output formed on the single-chip. The bandpass filtered output may be provided by an output buffer formed on the single-chip. The single-chip includes at least one tuning input to receive data for tuning stored in a data register formed on the single-chip. The data register provides control bits to the tuning components that include a programmable resistor responsive to the control bits to vary the programmable resistor to adjust programmed center frequency.

The present invention relates to nonlinear signal processing, and, in particular, to adaptive nonlinear filtering of real-, complex-, and vector-valued signals utilizing analog Nonlinear Differential Limiters (NDLs), and to adaptive real-time signal conditioning, processing, analysis, quantification, comparison, and control. More generally, this invention relates to methods, processes and apparatus for real-time measuring and analysis of variables, and to generic measurement systems and processes. This invention also relates to methods and corresponding apparatus for measuring which extend to different applications and provide results other than instantaneous values of variables. The invention further relates to post-processing analysis of measured variables and to statistical analysis. The NDL-based filtering method and apparatus enable improvements in the overall properties of electronic devices including, but not limited to, improvements in performance, reduction in size, weight, cost, and power consumption, and, in particular for wireless devices, NDLs enable improvements in spectrum usage efficiency.

Provided is a reconfigurable amplifier. The reconfigurable amplifier includes a gain circuit including a gain path configured to amplify an input signal, and a feed forward circuit including a feed forward path configured to receive the input signal and perform feed forward compensation on the input signal, and a first control circuit configured to perform the feed forward compensation in a first mode by activating the feed forward path, and deactivate the feed forward path in a second mode different from the first mode.

Method and implementation of gain-bandwidth product (GWB) tuning are disclosed. In an embodiment an operational amplifier (opamp) includes an input stage of the opamp including a differential device pair coupled to a tail device and configured to be responsive to a differential input signal for conducting a first current and an output stage of the opamp including a class AB interface stage circuit and a pair of output devices connected to the class AB interface stage circuit, wherein a first constant gm bias circuit is coupled to an input terminal of the class AB interface stage circuit.

Certain aspects of the present disclosure provide methods and apparatus for calibrating a tunable active filter. One example apparatus is a filter circuit that generally includes a tunable active filter comprising at least one amplifier and a first feedback path coupled between an input and an output of the at least one amplifier, the first feedback path comprising at least one switch; and an amplitude limiter coupled to the tunable active filter and comprising at least one transistor disposed in a second feedback path coupled between the input and the output of the at least one amplifier.