An amplifier circuit, for a capacitive acoustic transducer defining a sensing capacitor that generates a sensing signal as a function of an acoustic signal, has a first input terminal and a second input terminal, which are coupled to the sensing capacitor and: a dummy capacitor, which has a capacitance corresponding to a capacitance at rest of the sensing capacitor and a first terminal connected to the first input terminal; a first amplifier, which is coupled at input to the second input terminal and defines a first differential output of the circuit; a second amplifier, which is coupled at input to a second terminal of the dummy capacitor and defines a second differential output of the circuit; and a feedback stage, which is coupled between the differential outputs and the first input terminal, for feeding back onto the first input terminal a feedback signal, which has an amplitude that is a function of the sensing signal and is in phase opposition with respect thereto.

A loop compensation circuit includes a differential difference amplifier having a first transconductance stage with a first input terminal and a second input terminal. The first input terminal is coupled to a voltage reference and the second input terminal is coupled to a feedback node. The amplifier also includes a second transconductance stage having a third input terminal and a fourth input terminal. The third input terminal is coupled to a virtually specified fixed voltage and the fourth input terminal is coupled to a fixed specified voltage. The loop compensation circuit also includes a feedback impedance coupled between an output of the differential difference amplifier and the third input terminal and a second impedance between the third input terminal and the fixed specified voltage.

An RF quasi circulator circuit is described herein. In accordance with one example of the disclosure the circuit includes a receive port, a transmit port and an antenna port as well as a differential amplifier stage having a first input, a second input and an output that is coupled to the receive port. The circuit further includes a first phase shifting element and a second phase shifting element. The first phase shifting element is coupled between the transmit port and the first input of the differential amplifier and the second phase shifting element is coupled between the transmit port and the second input of the differential amplifier. A tunable impedance is coupled to the differential amplifier, and the antenna port is coupled to the first input of the differential amplifier. The tunable impedance is controlled to tune the damping in a signal path from the transmit port to the receive port.

A system according to examples of the present disclosure includes a battery charger electrically coupled to a battery and a battery charging circuit. The battery charging circuit includes an operational amplifier having a negative input to receive a pre-bias voltage, a positive input, an output, and a voltage offset. The battery charging circuit also includes a charge controller having an analog-to-digital converter to receive a voltage output from the output of the operational amplifier and a voltage supply to supply a voltage input into the positive input of the operation amplifier to cancel the voltage offset of the operational amplifier. In the example, the voltage output of the charge controller is a function of the voltage input of the charge controller.

This disclosure provides isolation for a medical amplifier by providing a low impedance path for noise across an isolation barrier. The low impedance path can include a capacitive coupling between a patient ground, which is isolated from control circuitry, and a functional ground of an isolation system that is isolated from earth ground. The low impedance path can draw noise current from an input of an amplifier of patient circuitry.

A power measurement system, including a voltage measurement circuit having a resistive network comprising first and second resistors connected in series on a first single substrate, and a feedback amplifier having an input in electrical communication with a point between the first and second resistors, and an output in electrical communication with the second resistor in a feedback configuration to output an attenuated voltage signal, and a transresistance current measurement circuit including a current transformer to transform an input primary current into a secondary current, a plurality of amplifiers configured in a cascading arrangement, and a feedback resistor configured in parallel with the cascaded amplifiers such that the combined gain of the cascaded amplifiers directs substantially all of the secondary current through the feedback resistor, wherein the system is selectively switchable between a voltage measurement mode and a current measurement mode.

Disclosed herein are related to a method of amplifying an input voltage based on cascaded charge pump boosting. The method includes storing, by a first capacitor, first electrical charges corresponding to an input voltage to obtain a second voltage. The method further includes amplifying, by a voltage amplifier, the second voltage according to the first electrical charges stored by the first capacitor to obtain a third voltage. The method further includes storing, by a second capacitor, second electrical charges according to the third voltage. The method further includes amplifying, by the voltage amplifier, the third voltage according to the second electrical charges stored by the second capacitor to obtain a fourth voltage.

A parallel input and dynamic cascaded OTA (operational transconductance amplifier includes: plural sub-OTAs which generate corresponding plural transconductance output currents according to corresponding plural differential input voltages; and at least one cascading capacitor which is cascaded between a first sub-OTA and a second sub-OTA. A second transconductance output current generated by the second sub-OTA is coupled through the cascading capacitor to generate a transient bias current on a common mode bias node of the first sub-OTA, thus providing the transient bias current to a differential pair circuit of the first sub-OTA in a case when a transient variation occurs in the differential input voltage corresponding to the first sub-OTA, so that a loop bandwidth and a response speed during a transient state are enhanced.

To provide a variable gain amplifier capable of correcting a DC offset voltage through simpler control even when a gain thereof is changed. A differential output type variable gain amplifier is equipped with a first voltage correction unit coupled to a preceding stage of a variable gain amplifier circuit and for outputting a first correction voltage to correct a potential difference generated between a first conductor provided with a first input resistor and a second conductor provided with a second input resistor, and a second voltage correction unit coupled to a subsequent stage of the variable gain amplifier circuit and for correcting a differential output. A control unit is configured to control the first correction voltage and a correction amount of a potential difference by the second voltage correction unit and thereby attenuate a DC offset voltage included in the differential output.

A matching network circuit for RF power amplifier circuit capable of odd harmonic rejection and even harmonic rejection in the differential mode and the common mode, respectively. The matching network circuit includes a differential mode filter with a differential resonant frequency and a passive component coupled to a virtual short circuit node at the differential mode filter, wherein a common mode filter with a common resonant frequency includes the differential mode filter and the passive component. As a result, two notch filters with different resonant frequencies are utilized for the common mode and the differential mode, respectively.