An amplifier circuit includes: a Schmidt trigger having an input electrically coupled to an input of the amplifier circuit, a switching network electrically coupled to an output of the Schmidt trigger, an inductor electrically coupled to the switching network, a first resistor electrically coupled to the inductor, a capacitor electrically coupled to the first resistor, a first feedback circuit that provides a first feedback signal to the input of the Schmidt trigger based on a voltage at a first node electrically coupled to the first resistor and to the capacitor, a second resistor electrically coupled to the output of the amplifier circuit, a third resistor electrically coupled to the second resistor, and a second feedback circuit that provides a second feedback signal to the input of the Schmidt trigger based on a voltage at a second node electrically coupled to the second resistor and to the third resistor.

An amplifier and a method of outputting a waveform of a music signal capable of outputting a waveform of a music signal exceeding a power supply voltage is provided. An amplifier includes a power supply, an input terminal for a music signal, an amplifying circuit which amplifies the music signal using the power supply, and a jumping-up circuit which is connected to an output end of the amplifying circuit and outputs a waveform exceeding a voltage value of the power supply.

Aspects disclosed herein eliminate audible disturbances that may occur when an audio amplifier is activated and deactivated. A feedback circuit is used to maintain a closed loop when transistors of a power output stage are activate or deactivated, thereby enabling the charge to build or dissipate without causing an audible disturbance. Further, in certain implementations, the power output stage may remain in an enable state for a period of time after deactivation of the audio amplifier regardless of whether an audio input signal is received enabling dissipation of charge without causing an audible disturbance.

An example apparatus includes: a first voltage source, a first amplifier having a noninverting input adapted to be coupled to a photodiode anode and coupled to the first voltage source, an inverting input adapted to be coupled to a photodiode cathode, and an output, a first resistor coupled to the first amplifier inverting input and to the first amplifier output, a first capacitor coupled to the inverting input of the first amplifier and the first amplifier output, and a second voltage source different from the first voltage source. There is a second amplifier having a noninverting input, an inverting input and an output. The noninverting input is coupled to the output of the first amplifier, the inverting input is coupled to the second voltage source, and there is a second resistor coupled to the inverting input and the output of the second amplifier.

An amplifier circuit includes: a Schmidt trigger having an input electrically coupled to an input of the amplifier circuit, a switching network electrically coupled to an output of the Schmidt trigger, an inductor electrically coupled to the switching network, a first resistor electrically coupled to the inductor, a capacitor electrically coupled to the first resistor, a first feedback circuit that provides a first feedback signal to the input of the Schmidt trigger based on a voltage at a first node electrically coupled to the first resistor and to the capacitor, a second resistor electrically coupled to the output of the amplifier circuit, a third resistor electrically coupled to the second resistor, and a second feedback circuit that provides a second feedback signal to the input of the Schmidt trigger based on a voltage at a second node electrically coupled to the second resistor and to the third resistor.

An amplification circuit configured to generate an output signal by differentially amplifying first and second input signals. The first and second input signals are a differential signal pair. Alternatively, the first input signal is a single-ended signal, and the second input signal is a reference signal. The amplification circuit is configured to perform a differential amplification operation by increasing a gain for generating an output signal based on the first input signal.

A circuit that outputs a current which is proportional to an input voltage includes input and output terminals, a comparator, first and second transistors, an inductor, a first resistor, and a differential amplifier. A first input terminal of the comparator is coupled to the input terminal of the circuit, and a second input terminal of the comparator is coupled to an output terminal of the comparator. The first and second transistors are coupled to the output terminal of the comparator. The inductor is coupled to the first and second transistors. The first resistor is coupled between the inductor and the output terminal of the circuit. The differential amplifier includes a first input terminal coupled to a first terminal of the first resistor, a second input terminal coupled to a second terminal to the first resistor, and an output terminal coupled to the first input terminal of the comparator.

In one general aspect, an amplifier can include an input amplifier circuit configured to receive a bias current and receive, as an input, a signal pair connected differentially to the input amplifier circuit, the input amplifier circuit configured to output a differential output signal pair based on the received differential input signal pair, a feedback amplifier circuit configured to receive an average of the differential output signal pair and configured to provide a bias setting output for controlling the bias current, and an output buffer circuit configured to buffer the differential output signal pair, the buffering resulting in a buffered differential output signal pair capable of driving a resistive load.

A circuit that outputs a current which is proportional to an input voltage includes input and output terminals, a comparator, first and second transistors, an inductor, a first resistor, and a differential amplifier. A first input terminal of the comparator is coupled to the input terminal of the circuit, and a second input terminal of the comparator is coupled to an output terminal of the comparator. The first and second transistors are coupled to the output terminal of the comparator. The inductor is coupled to the first and second transistors. The first resistor is coupled between the inductor and the output terminal of the circuit. The differential amplifier includes a first input terminal coupled to a first terminal of the first resistor, a second input terminal coupled to a second terminal to the first resistor, and an output terminal coupled to the first input terminal of the comparator.

An amplifier includes a first input circuit, a second input circuit, a first compensation circuit, a second compensation circuit. The first input circuit changes a voltage level of the negative output node based on a first input signal. The second input circuit changes a voltage level of the positive output node based on a second input signal. The first compensation circuit changes the voltage level of the positive output node based on the first input signal. The second compensation circuit changes the voltage level of the negative output node based on the second output signal.