A tunable filter is provided. The tunable filter includes: a filter input; a filter output; at least one feedback loop coupled between the filter output and the filter input, where the at least one feedback loop includes at least one tunable feedback capacitance which is configured to tune a cut-off frequency of the tunable filter; and an active element, coupled between the filter input and the filter output and configured to drive the at least one tunable feedback capacitance, the active element having a transfer function with a primary pole and at least one secondary pole, where the active element includes a first stabilization element that is coupled to a first internal node of the active element.

Data transfer rates input to and output from electronic devices are a function of I/O pad circuit structure. The load capacitance of an I/O pad may reduce the bandwidth of an I/O circuit. A reduced pad capacitance circuit may be used to reduce or eliminate the positive and physical pad capacitance associated with a capacitive pad. This negative capacitance reduces or minimizes poor signal quality arising from large pad capacitance. This improved signal may be fed into a comparator, where the signal may be improved further using an equalizer. The use of negative capacitance circuit will increase the transmit and receive signaling quality of I/O interfaces.

Aspects of the disclosure are directed to auto-sweeping impedance-matching circuitry that matches an impedance of an RF antenna. As may be implemented in accordance with one or more embodiments, a transmitter that is configured and arranged to transmit signals to remote devices via the RF antenna, is used to communicate a plurality of test signals to the impedance-matching circuitry, with each test signal having a designated frequency and/or test signal pattern that is different than the designated frequency and/or test signal pattern of the other test signals. A characteristic of each of the test signals as passed through the impedance-matching circuitry is detected. For each of the test signals generated for the auto-sweep, the detected characteristic is compared to an expected characteristic for the test signal, and an output indicative of compliance of the impedance-matching circuitry with a design specification is generated and transmitted in response to the comparison.

A tunable filter is provided. The tunable filter includes: a filter input; a filter output; at least one feedback loop coupled between the filter output and the filter input, where the at least one feedback loop includes at least one tunable feedback capacitance which is configured to tune a cut-off frequency of the tunable filter; and an active element, coupled between the filter input and the filter output and configured to drive the at least one tunable feedback capacitance, the active element having a transfer function with a primary pole and at least one secondary pole, where the active element includes a first stabilization element that is coupled to a first internal node of the active element.

Aspects of the disclosure are directed to auto-sweeping impedance-matching circuitry that matches an impedance of an RF antenna. As may be implemented in accordance with one or more embodiments, a transmitter that is configured and arranged to transmit signals to remote devices via the RF antenna, is used to communicate a plurality of test signals to the impedance-matching circuitry, with each test signal having a designated frequency and/or test signal pattern that is different than the designated frequency and/or test signal pattern of the other test signals. A characteristic of each of the test signals as passed through the impedance-matching circuitry is detected. For each of the test signals generated for the auto-sweep, the detected characteristic is compared to an expected characteristic for the test signal, and an output indicative of compliance of the impedance-matching circuitry with a design specification is generated and transmitted in response to the comparison.

The disclosure relates to a tunable filter. The tunable filter includes: a filter input; a filter output; at least one feedback loop coupled between the filter output and the filter input, where the at least one feedback loop includes at least one tunable feedback capacitance which is configured to tune a cut-off frequency of the tunable filter; and an active element, coupled between the filter input and the filter output and configured to drive the at least one tunable feedback capacitance, the active element having a transfer function with a primary pole and at least one secondary pole, where the active element includes a first stabilization element that is coupled to a first internal node of the active element.

The disclosure relates to a tunable filter. The tunable filter includes: a filter input; a filter output; at least one feedback loop coupled between the filter output and the filter input, where the at least one feedback loop includes at least one tunable feedback capacitance which is configured to tune a cut-off frequency of the tunable filter; and an active element, coupled between the filter input and the filter output and configured to drive the at least one tunable feedback capacitance, the active element having a transfer function with a primary pole and at least one secondary pole, where the active element includes a first stabilization element that is coupled to a first internal node of the active element.

Two types of high-pass filter circuit and a band-pass filter circuit are provided. Both types of high-pass filter circuit include a capacitor configured to input an input signal, a resistor connected between an output terminal of the capacitor and a prescribed bias voltage, and a signal output circuit connected to the output terminal of the capacitor and configured to buffer-amplify the input signal for output. In one of the two types of high-pass filter circuits, the resistor is formed on an SOI semiconductor substrate and includes two PN junction diodes that are inversely connected to each other in parallel. In the other one of the high-pass filter circuits, the resistor is formed on an SOI semiconductor substrate and includes two MOS transistors that are inversely connected to each other in parallel.