The present invention is directed to electrical circuits and techniques thereof. More specifically, embodiments of the present invention provide a differential amplifier that has a differential amplifier section, a current source, and a feedback section. The differential amplifier section comprises NMOS transistors that receives two voltage inputs and generate a differential output. The current source provides a long tail for the differential amplifier section. The feedback section generates a feedback voltage based on a reference bias voltage. The feedback voltage is used by an amplifier to control the current source and to keep the biasing and gain of the differential amplifier substantially constant. There are other embodiments as well.

A variable gain amplifying circuit incorporates an operational amplifier, an input device, a feedback device, a transconductance circuit, and a dynamic biasing circuit. The operational amplifier has an output terminal providing an amplified difference output signal. The input device has a first terminal receiving a first input signal, and a second terminal coupled to a first input terminal of the operational amplifier. The feedback device is coupled between the first input terminal of the operational amplifier and the output terminal of the operational amplifier. The dynamic biasing circuit generates a bias current to according to a set value. The transconductance circuit converts the difference between the first input signal and a second input signal into an analog output current flowing through the feedback device. The analog output current of the transconductance circuit is varied according to the bias current.

An analogue amplification device comprises a first stage with a common base or gate transistor that receives the modulated input current on its emitter or its source and the output signal of this first stage corresponds to the signal of the collector, a second stage formed by a follower amplifier comprising a transistor with a common collector or drain setup, a third stage that comprises a transistor with a common emitter setup, and a fourth stage that is an amplifying stage with means allowing the realization of, on the one hand, an amplification, and on the other hand, a matching of impedance. The device can be applied to a laser anemometer with optical retro-injection.

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 buffer amplifier, which is coupled at input to the second input terminal and defines a first differential output of the circuit; a second buffer 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 Low Voltage Differential Signaling (LVDS) compliant receiver includes a differential amplifier having inputs and outputs. A first input coupling capacitor and second input coupling capacitor are electrically coupled to each of the first differential input and the second differential input, respectively. The receiver also includes a first and a second regenerative feedback latching mechanism, and the first regenerative feedback latching mechanism is electrically coupled between the first input coupling capacitor and the first differential output. The second regenerative feedback latching mechanism is electrically coupled between the second input coupling capacitor and the second differential output. An integrated circuit substrate includes each of the differential amplifier, the first differential input, the second differential input, the first differential output, the second differential output, the first regenerative feedback latching apparatus, and the second regenerative feedback latching apparatus are contained thereon. The first and the second input coupling capacitor are on-chip.

An electronic circuit for amplifying signals with two components in phase quadrature, which includes: a feedback amplifier with a feedback capacitor; a switch that drives charging and discharging of the feedback capacitor; an additional capacitor; and a coupling circuit, which alternatively connects the additional capacitor in parallel to the feedback capacitor or else decouples the additional capacitor from the feedback capacitor. The switch opens at a first instant, where a first one of the two components assumes a first zero value; the coupling circuit decouples the additional capacitor from the feedback capacitor in a way synchronous with a second instant, where the first component assumes a second zero value.

A hi-fi headphone device with two speakers, an integrated pentode vacuum tube, and a battery. The battery is electrically connected to direct and bias circuits, to provide proper voltage to the vacuum tube amplifiers, wherein input signal is amplified and output to buffer circuits and impedance is matched between the tube and output speaker terminals.

An amplifier includes a first input branch and a second input branch that form a differential input stage and a current mirror connected to the differential input. The current mirror is governed as a function of a common mode feedback signal applied to a control node of the current mirror. A second, amplification, stage includes a branch flowing through which is a current, which is a function of the current that flows in the first input branch, and is in turn connected to a first output branch. A capacitive element is coupled between the control node and the second stage. The circuit is symmetrical with respect to the input stage.

Various envelope tracking amplifiers are presented that can be switched between an ET (envelope tracking) mode and a non-ET mode. Switches and/or tunable components are utilized in constructing the envelope tracking amplifiers that can be switched between the ET mode and the non-ET mode.

An amplifier circuit is provided. The amplifier circuit includes an amplifier stage; a plurality of variable transistors connected to the amplifier stage; a transconductor connected to at least one of the plurality of variable transistors; and a hybrid differential envelope detector and full-wave rectifier connected to the transconductor.