A circuit comprises a Sallen-Key filter, which includes a source follower that implements a unity-gain amplifier; and a programmable-gain amplifier coupled to the Sallen-Key filter. The circuit enables programmable gain via adjustment to a current mirror copying ratio in the programmable-gain amplifier, which decouples the bandwidth of the circuit from its gain settings. The programmable-gain amplifier can comprise a differential voltage-to-current converter, a current mirror pair, and programmable output gain stages. The Sallen-Key filter and at least one branch in the programmable-gain amplifier can comprise transistors arranged in identical circuit configurations.

The embodiments of the present disclosure provide a method and system for adjusting a passband width of a filter. The method includes determining an initial passband width, controlling a filter according to the initial passband width to filter signals to be processed, and correcting the initial passband width according to a first frequency at which a peak spectrum line corresponding to the filtered signals is located.

An IC includes an RC filter, a doped layer under a first dielectric layer, a polysilicon layer on the first dielectric layer providing a polysilicon plate for a capacitor of the filter, and gate(s) for MOSFET(s). A second dielectric layer is on the polysilicon plate. An input contact is on one end of the polysilicon plate and an output contact is on the opposite end. A metal layer includes metal providing contact to at least input contact and metal providing contact to the output contact. Analog circuitry includes the MOSFET having an I/O node coupled to the RC filter.

A filter circuit includes a filter and a current mode programmable gain amplifier, where the filter circuit is configured to filter an input signal to obtain an output signal. The filter is supplied with the input signal. The filter comprises at least one current extraction element configured to extract a first output current signal. The current mode programmable gain amplifier is configured to receive and amplify the first output current signal to obtain an amplified current signal. The output signal is derived from the amplified current signal.

An active filter and an analog-to-digital converter (ADC) configured to suppress out-of-band peaking. An active filter may include an active device configured to provide a power gain to an input signal, a feedback network configured to connect an output of the active device to an input of the active device, and an input impedance network configured to couple the input signal to the input of the active device. A combination of the feedback network and the input impedance network is configured to provide frequency response properties of the active filter such that a frequency domain signal transfer function of the active filter has a constant in numerator.

A low-pass filter circuit comprising: a low-pass filter input terminal; a low-pass filter output terminal; a reference terminal; at least three filter resistors connected in series with each other between the low-pass filter input terminal and the low-pass filter output terminal, such that there is a resistor-connecting-node between each adjacent pair of filter resistors; a plurality of filter capacitors, one for each of the resistor-connecting-nodes, wherein each of the filter capacitors is connected between an associated resistor-connecting-node and the reference terminal; and a branch connected in parallel with the at least three filter resistors, wherein the branch comprises a bridging capacitor and a bridging resistor in series with each other.

The embodiments of the present disclosure provide a method and system for adjusting a passband width of a filter. The method includes determining an initial passband width, controlling a filter according to the initial passband width to filter signals to be processed, and correcting the initial passband width according to a first frequency at which a peak spectrum line corresponding to the filtered signals is located.

A circuit comprises a Sallen-Key filter, which includes a source follower that implements a unity-gain amplifier; and a programmable-gain amplifier coupled to the Sallen-Key filter. The circuit enables programmable gain via adjustment to a current mirror copying ratio in the programmable-gain amplifier, which decouples the bandwidth of the circuit from its gain settings. The programmable-gain amplifier can comprise a differential voltage-to-current converter, a current mirror pair, and programmable output gain stages. The Sallen-Key filter and at least one branch in the programmable-gain amplifier can comprise transistors arranged in identical circuit configurations.

An IC includes an RC filter, a doped layer under a first dielectric layer, a polysilicon layer on the first dielectric layer providing a polysilicon plate for a capacitor of the filter, and gate(s) for MOSFET(s). A second dielectric layer is on the polysilicon plate. An input contact is on one end of the polysilicon plate and an output contact is on the opposite end. A metal layer includes metal providing contact to at least input contact and metal providing contact to the output contact. Analog circuitry includes the MOSFET having an I/O node coupled to the RC filter.

A filter circuit includes a filter and a current mode programmable gain amplifier, where the filter circuit is configured to filter an input signal to obtain an output signal. The filter is supplied with the input signal. The filter comprises at least one current extraction element configured to extract a first output current signal. The current mode programmable gain amplifier is configured to receive and amplify the first output current signal to obtain an amplified current signal. The output signal is derived from the amplified current signal.