An electronic circuit including: a differential multiplier circuit with a first differential input and a second differential input and a differential output; and a phase locked loop (PLL) circuit including: (1) a balanced differential mixer circuit with a first differential input electrically connected to the differential output of the differential multiplier circuit, a second differential input, and an output; (2) a loop filter having an output and an input electrically connected to the output of the balanced differential mixer circuit; and (3) a voltage controlled oscillator (VCO) circuit having an input electrically connected to the output of the loop filter and with an output electrically feeding back to the second differential input of the balanced differential mixer circuit.

An amplifier circuit includes a first amplifier including input terminals and configured to amplify a signal, the signal being input into one of the input terminals; a second amplifier into which positive and negative outputs of the first amplifier are each input; a first low-pass filter into which outputs of the second amplifier are input; a high-pass filter into which outputs of the first amplifier are input; a second low-pass filter into which outputs of the high-pass filter are input; and a difference circuit configured to output a difference between outputs of the first low-pass filter and outputs of the second low-pass filter, wherein an output of the difference circuit is input into another one of the input terminals of the first amplifier.

A correlated double sampling integrating circuit is provided. The circuit includes: a sampling and holding module, an energy storage unit and a feedback module. The sampling and holding module is configured to perform sampling and holding for different input signals. The energy storage unit is configured to store charges corresponding to the input signals upon the sampling and holding to generate node signals, and the feedback module is configured to form a negative feedback loop with the energy storage unit to control node signals at an integrating stage to keep consistent with node signals at a resetting stage and prevent output jump of the correlated double sampling integrating circuit. The correlated double sampling integrating circuit reduces noise, and prevents or weakens output jump of the correlated double sampling integrating circuit caused by the increase of the count of integrations.

A differential input amplification-stage circuit comprises a voltage unit, first and second bulk-driven transistors, first and second mirror current sources, and a differential amplifier unit. The first and the second bulk-driven transistors respectively receive first and second input voltages, and converts the first and the second input voltages into first and second output currents. The differential amplifier unit separately outputs first and second adjustment currents under an action of voltages output by the first to the third voltage output ends. The first and the second mirror current sources respectively output first and second predetermined currents according to the first output current and the first adjustment current, and the second output current and the second adjustment current, so as to maintain transconductance constancy of the differential input amplification-stage circuit. Therefore, output stability is improved.

Techniques for monitoring a distortion signal of a power amplifier circuit, where the output of a distortion monitoring circuit includes little or no fundamental signal and closely represents the actual distortion of the amplifier circuit of a wired communications system. The power amplifier circuit can generate a distortion feedback signal that does not affect the power amplifier's output power capability, e.g., no inherent loss in the fundamental output of the amplifier. That is, using a distortion monitor circuit, the power amplifier circuit can resolve a distortion feedback signal from the intended output signal of the output power amplifier circuit.

Techniques for limiting the output voltage of an amplifier without directly affecting an output current of the amplifier are provided. In an example, an amplifier can include a plurality of amplifier stages configured to receive an input voltage and to provide an output voltage as a function of the input voltage, and a comparator configured to receive a voltage limit and a representation of the output voltage of the amplifier, to adjust current at an input to a first amplifier stage of the plurality of amplifier stages when the output voltage violates the voltage limit, and to clamp the output voltage at an offset from the voltage limit.

A correlated double sampling integrating circuit is provided. The circuit includes: a sampling and holding module, an energy storage unit and a feedback module. The sampling and holding module is configured to perform sampling and holding for different input signals. The energy storage unit is configured to store charges corresponding to the input signals upon the sampling and holding to generate node signals, and the feedback module is configured to form a negative feedback loop with the energy storage unit to control node signals at an integrating stage to keep consistent with node signals at a resetting stage and prevent output jump of the correlated double sampling integrating circuit. The correlated double sampling integrating circuit reduces noise, and prevents or weakens output jump of the correlated double sampling integrating circuit caused by the increase of the count of integrations.

A transimpedance amplifier circuit includes a feedback control loop that generates a compensation current at an input of a transimpedance amplifier. The feedback control loop includes a differential integrator with an integration capacitor. A time constant associated with charging the integration capacitor is variable as a function of a pre-charge control signal. During a pre-charge phase, the pre-charge control signal is set to a first value so as to set the time constant associated with charging the integration capacitor to a first time constant value. During an operation phase, the pre-charge control signal is set to a second value so as to increase the time constant associated with charging the integration capacitor to a second time constant value greater than the first time constant value for the pre-charge phase.

An impedance measurement circuit for determining a sense current of a guard-sense capacitive sensor operated in loading mode. The circuit includes a periodic signal voltage source for providing a periodic measurement voltage, a sense current measurement circuit, a differential amplifier that is configured to sense a complex voltage difference between the sense electrode and the guard electrode, a demodulator for obtaining, with reference to the periodic measurement voltage, an in-phase component and a quadrature component of the sensed complex voltage difference, and control loops for receiving the in-phase component and the quadrature component, respectively. An output signal of the first control loop and an output signal of the second control loop are usable to form a complex voltage that serves as a complex reference voltage for the sense current measurement circuit.

An electronic circuit including: a differential multiplier circuit with a first differential input and a second differential input and a differential output; and a phase locked loop (PLL) circuit including: (1) a balanced differential mixer circuit with a first differential input electrically connected to the differential output of the differential multiplier circuit, a second differential input, and an output; (2) a loop filter having an output and an input electrically connected to the output of the balanced differential mixer circuit; and (3) a voltage controlled oscillator (VCO) circuit having an input electrically connected to the output of the loop filter and with an output electrically feeding back to the second differential input of the balanced differential mixer circuit.