An operational amplifier includes: a first amplifier stage, configured to generate first output voltages according to first input voltages; a second amplifier stage, configured to generate second output voltages according to the first output voltages; a second output stage circuit, configured to replicate an equivalent or a scaled-down version of the first output stage circuit; a first common-mode feedback circuit, configured to keep an output common-mode voltage of the second output stage circuit at a predetermined value; a logic loop circuit configured to, when the operational amplifier operates in a direct current calibration phase, adjust a difference between the first output voltages; a bias circuit, configured to generate a voltage close to a common-mode voltage of the first output voltages produced after the operational amplifier is turned on, the voltage serving as a reference voltage of a second common-mode feedback circuit.

An operational amplifier includes: a first amplifier stage, configured to generate first output voltages according to first input voltages; a second amplifier stage, configured to generate second output voltages according to the first output voltages; a second output stage circuit, configured to replicate an equivalent or a scaled-down version of the first output stage circuit; a first common-mode feedback circuit, configured to keep an output common-mode voltage of the second output stage circuit at a predetermined value; a logic loop circuit configured to, when the operational amplifier operates in a direct current calibration phase, adjust a difference between the first output voltages; a bias circuit, configured to generate a voltage close to a common mode voltage of the first output voltages produced after the operational amplifier is turned on, the voltage serving as a reference voltage of a second common-mode feedback circuit.

A high-gain, low power, electronic amplifier for amplification of a low magnitude voltage signal through a comparator-integrator amplification method for energy-aware applications is disclosed. The electronic amplifier comprises: a comparator arrangement with at least one comparator unit adapted to receive a first voltage signal to be amplified and a first feedback voltage signal, and to generate a first two-level voltage comparison signal; a integrator arrangement to receive the first two-level voltage comparison signal and generate a first amplifier output signal corresponding to an amplification of the voltage signal to be amplified; and a first feedback network to receive the first amplifier output signal and generate the first feedback voltage signal.

A compensation circuit of a power amplifier includes a varactor, a voltage sensor and a control circuit. The varactor is coupled to an input terminal of the power amplifier. The voltage sensor is arranged for detecting an amplitude of an input signal of the power amplifier to generate a detecting result. The control circuit is coupled to the varactor and the voltage sensor, and is arranged for controlling a bias voltage of the varactor to adjust a capacitance of the varactor according to the detecting result.

A compensation circuit of a power amplifier includes a varactor, a voltage sensor and a control circuit. The varactor is coupled to an input terminal of the power amplifier. The voltage sensor is arranged for detecting an amplitude of an input signal of the power amplifier to generate a detecting result. The control circuit is coupled to the varactor and the voltage sensor, and is arranged for controlling a bias voltage of the varactor to adjust a capacitance of the varactor according to the detecting result.

A wideband highly-linear buffer circuit exhibiting a low output impedance comprises a first PFET (PFET1), a second PFET (PFET2), a first NFET (NFET1), and a second NFET (NFET2). Sources of PFET1 and PFET2 are coupled to VDD. PFET1's drain is coupled to an output lead. PFET2 acts as a current source. NFET1's drain is coupled to PFET2's drain and to PFET1's gate. NFET1's source is coupled to the output lead. NFET2's source is coupled to ground. NFET2's drain is coupled to NFET1's source and to the output lead. NFET1's gate is AC coupled to a first input lead. In a single-ended input example, NFET2's gate is AC coupled NFET1's drain. In a differential input example, NFET2's gate is AC coupled to a second input lead. In another differential input example, PFET2 is not just a current source, but rather PFET2's gate is AC coupled to the first input lead.

A voltage regulator is described. It includes an amplification stage to control a voltage level of a first gain node and of a second gain node in response to an input voltage, to activate a first and a second output stage, respectively. It further includes the first output stage to source a current at an output node of the voltage regulator from a first potential. The voltage regulator includes the second output stage to sink a current at the output node to a second potential. The voltage regulator includes a first operating point control circuit to set the voltage level of the first gain node such that a first maintenance current is sourced by the first output stage; and/or a second operating point control circuit to set the voltage level of the second gain node such that a second maintenance current is sunk by the second output stage.

A voltage regulator is described. It comprises an amplification stage to control a voltage level of a first gain node and of a second gain node in response to an input voltage, to activate a first and a second output stage, respectively. It further comprises the first output stage to source a current at an output node of the voltage regulator from a first potential. The voltage regulator comprises the second output stage to sink a current at the output node to a second potential. The voltage regulator comprises a first operating point control circuit to set the voltage level of the first gain node such that a first maintenance current is sourced by the first output stage; and/or a second operating point control circuit to set the voltage level of the second gain node such that a second maintenance current is sunk by the second output stage.

A voltage regulator is described. It includes an amplification stage to control a voltage level of a first gain node and of a second gain node in response to an input voltage, to activate a first and a second output stage, respectively. It further includes the first output stage to source a current at an output node of the voltage regulator from a first potential. The voltage regulator includes the second output stage to sink a current at the output node to a second potential. The voltage regulator includes a first operating point control circuit to set the voltage level of the first gain node such that a first maintenance current is sourced by the first output stage; and/or a second operating point control circuit to set the voltage level of the second gain node such that a second maintenance current is sunk by the second output stage.