An amplifier includes a first stage and a second stage. The first stage includes a first output and a second output. The second stage includes an output, a first transistor and a second transistor. The first transistor includes a drain coupled to the first output of the first stage, and a source coupled to the output of the second stage. The second transistor includes a drain coupled to the second output of the first stage, and a gate coupled to the output of the second stage.

An amplifier includes a first stage and a second stage. The first stage includes a first output, and a second output. The second stage includes a first transistor, a second transistor, and a common-mode circuit. The first transistor includes a drain coupled to the first output of the first stage. The second transistor includes a drain coupled to the second output of the first stage. The common-mode circuit includes a reversible current mirror circuit coupled to the drain of the first transistor and the drain of the second transistor.

An amplifier circuit has an output stage, a first current source, a second current source, a third current source, a fourth current source, and a voltage clamping voltage. The output stage has a first P-type transistor and a first N-type transistor. The voltage clamping circuit receives a first bias voltage and a second bias voltage, and has a first end and a second end. When a second input current is positive current and the input current is a negative current or a zero current, the first end provides a first clamping voltage greater than the first bias voltage to a gate of the first P-type transistor. When the first input current is positive and the second input current is a negative current or zero current, the second end provides a second clamping voltage lower than the second bias voltage to a gate of the first N-type transistor.

A semiconductor device includes a semiconductor chip that has a main surface, a device region that is demarcated at the main surface, a differential amplifier that is formed in the device region and that amplifies and outputs a differential signal input to the differential amplifier, an insulation layer that covers the device region on the main surface, and a shield electrode that is incorporated in the insulation layer such as to conceal the device region in a plan view and that is fixed to a ground potential.

Techniques for biasing output transistor of a push-pull amplifier output stage are provided. In certain applications the techniques can improve efficiency of the amplifier. In an example, a circuit can include an output stage including first and second output transistors, a first scaled replica transistor corresponding to the first output transistor, and an amplifier circuit in a feedback arrangement for biasing a gate of the first output transistor at a level that, at a specified stand-by current level of the first output transistor, reproduces a voltage difference between the drain and source terminals of the first output transistor across the drain and source terminals of the first replica transistor.

A transimpedance amplifier circuit includes an amplifier circuit that converts a current signal into a voltage signal with a gain being varied based on a control signal and a gain control circuit that generates the control signal based on an amplitude of the voltage signal. The gain control circuit includes a detection circuit that generates an amplitude-detection-signal in accordance with the amplitude of the voltage signal, a setting circuit that generates an amplitude-reference-signal, a differential voltage generation circuit that generates a differential-voltage-signal obtained by offsetting a voltage difference between the amplitude-detection-signal and the amplitude-reference-signal based on an amplitude-setting-signal, an operational transconductance amplifier (OTA) that generates a differential-current-signal based on the differential-voltage-signal, and a variable capacitor circuit having a variable capacitance being varied based on the amplitude-setting-signal, and configured to be charged/discharged by the differential-current-signal and output a charging voltage. The control signal is generated based on the charging voltage.

The present invention provides a linear amplifier including an amplifier stage, a DC-shifting stage, a compensation network and a power stage. The amplifier stage is configured to generate a first signal and a second signal. The DC-shifting stage is configured to adjust a DC voltage of the first signal and a DC voltage of the second signal to generate an adjusted first signal and an adjusted second signal. The compensation network is configured to generate a first driving signal and a second driving signal according to the first signal, the second signal, the adjusted first signal and the adjusted second signal. The power stage is configured to generate an output signal according to the first driving signal and the second driving signal.

A rectifying circuit includes: a voltage-current converting circuit that converts an input voltage into a current; a first transistor and a second transistor that are connected in series and that are connected to a first node into which the current converted by the voltage-current converting circuit flows; a third transistor and a fourth transistor that are connected in series, and that respectively mirror a current flowing through the first transistor and a current flowing through the second transistor; and a first diode that is connected between a second node connected to the third transistor and the fourth transistor, and an output terminal.

An amplifier includes an input circuit that amplifies a difference between a first input voltage and a second input voltage to generate a first current and a second current. A positive feedback circuit amplifies a difference between the first current and the second current to generate a third current and a fourth current and outputs a difference between the third current and the fourth current through an output node. A temperature compensation circuit adjusts an amplification factor of the positive feedback circuit in response to a change of temperature.

An operational amplifier includes a differential input stage that amplifies a differential input signal to generate an intermediate signal; an amplification stage including an output transistor that is connected between an output terminal and a fixed voltage line, and is driven according to the intermediate signal; and an assist circuit, wherein the assist circuit includes: a first transistor connected in parallel with the output transistor; and a drive circuit that drives the first transistor according to a gate voltage of the output transistor.