Various embodiments of the present technology may comprise methods and apparatus for an amplifier circuit. Methods and apparatus for an amplifier circuit according to various aspects of the present invention may be utilized in a digital-to-analog converter. The amplifier circuit may comprise a first operational amplifier with a feedback circuit. The feedback circuit may comprise an inverting amplifier circuit.

Various embodiments of the present technology may provide methods and apparatus for an amplifier integrated circuit. The amplifier integrated circuit may provide two amplifiers, one amplifier set to a low gain bandwidth product to amplify at a higher speed and the other amplifier set to a high gain bandwidth product to amplify at a lower speed. The amplifier integrated circuit may further provide a switching circuit connected to the amplifiers, wherein the switching circuit is responsive to a control signal and operates to selectively activate the high speed amplifier and the low speed amplifier in sequence.

Disclosed herein is an amplification circuit that outputs an output signal formed by amplifying a differential signal between a first input terminal and a second input terminal using an operating amplifier and a plurality of resistors, the amplification circuit including an adjustment circuit configured to adjust a frequency property of the output signal for an in-phase alternating current signal input between the first input terminal and the second input terminal. The adjustment circuit is connected to one input terminal of the first input terminal and the second input terminal through one or more resistors, the adjustment circuit includes a capacitor part whose capacitance is set to be variable, and the adjustment is realized through variable setting of the capacitance of the capacitor part.

A low energy transmitter is provided. The transmitter includes an antenna circuit wherein the antenna circuit has an antenna positive node interface (Vop) and an antenna negative node interface (Von); a reference voltage source that supplies a reference voltage to the antenna circuit; and a common mode feedback (CMFB) circuit coupled to the antenna circuit that receives from the antenna circuit inputs from the Vop and the Von and supplies at least one signal to the antenna circuit.

An amplifier includes an input stage, a folded cascode stage, and a class AB output stage. The folded cascode stage is coupled to the input stage. The class AB output stage is coupled to the folded cascode stage. The class AB output stage includes a high-side output transistor, a low-side output transistor, and a high-side feedback circuit that is coupled to the high-side output transistor. The high-side feedback circuit includes a high-side sense transistor and a high-side feedback transistor. The high-side sense transistor includes a control terminal that is coupled to a control terminal of the high-side output transistor. The high-side feedback transistor is coupled to an output of the high-side sense transistor and to the folded cascode stage. A first output of the folded cascode stage is coupled to the control terminal of the high-side sense transistor and to the control terminal of the high-side output transistor.

There is provided a chopper stabilized amplifier with an input bias current reduced. The chopper stabilized amplifier includes a main amplifier and a correction circuit. The correction circuit includes a second gm amplifier of a full differential type. A first selector and the second gm amplifier are coupled to each other without DC blocking capacitors. The differential input state of the second gm amplifier is configured with a depletion-type transistor.

An operational amplifier includes a differential amplification circuit configured to receive and amplify an input voltage to generate an output voltage, and receive a feedback signal, and the feedback signal adjusts a common-mode voltage of the output voltage, a reference voltage generation circuit configured to detect status information of the operational amplifier, and generate a reference voltage based on the status information, where the status information includes a temperature or an operating voltage of the operational amplifier, and a common-mode feedback circuit configured to receive the output voltage and the reference voltage, and provide the feedback signal to the differential amplification circuit based on the output voltage and the reference voltage.

Apparatus useful for receiving or transmitting voltage signals might include a current generator having first and second inputs and configured to generate a current flow between first and second outputs responsive to a voltage difference between its first and second inputs. The apparatus might further include a feedback amplifier having a first input connected to the first output of the current generator, a second input connected to the second output of the current generator, a first voltage signal node connected to its first input through a first resistance, and a second voltage signal node connected to its second input through a second resistance, wherein a first inverter is connected in parallel with the first resistance, a second inverter is connected in parallel with the second resistance, and a pair of cross-coupled inverters are connected between the first voltage signal node and the second voltage signal node.

Apparatus useful for receiving or transmitting voltage signals might include a current generator having first and second inputs and configured to generate a current flow between first and second outputs responsive to a voltage difference between its first and second inputs. The apparatus might further include a feedback amplifier having a first input connected to the first output of the current generator, a second input connected to the second output of the current generator, a first voltage signal node connected to its first input through a first resistance, and a second voltage signal node connected to its second input through a second resistance, wherein a first inverter is connected in parallel with the first resistance, a second inverter is connected in parallel with the second resistance, and a pair of cross-coupled inverters are connected between the first voltage signal node and the second voltage signal node.

Various embodiments of the present technology comprise a method and apparatus for an operational amplifier with a variable gain-bandwidth product. According to various embodiments, an amplifier circuit comprising the operational amplifier operates in multiple stages and provides a low gain-bandwidth and a high gain-bandwidth.