An amplifier includes an amplifying device and a bias circuit for providing a bias voltage for the amplifying device. The bias circuit is configured to provide the bias voltage in dependence of an output signal of an optical coupling arrangement which provides for electrical isolation.

The disclosed technology relates to a method for improving performance of a feedback circuit comprising an amplifier and a feedback network, wherein the feedback circuit has at least one tunable component. In one aspect, the method comprises measuring first amplitude values at an input of the amplifier and second amplitude values at an output of the amplifier, estimating a linear open-loop gain of the amplifier based on both the amplitude values, estimating a linear finite gain error based on the estimated gain and the second amplitude values, subtracting the linear finite gain error from the first amplitude values to derive a set of samples containing second error information, deriving an signal-to-noise-plus-distortion ratio estimate based on the variance of the set of samples and a variance of the second amplitude values, and adjusting the feedback circuit in accordance with the signal-to-noise-plus-distortion ratio estimate.

A class-D amplifier that amplifies an input audio signal includes: a push-pull circuit that has at least two switching transistors; an electric current suppressor that is disposed between the push-pull circuit and a power source that supplies electric power to the push-pull circuit; a switch that is connected in parallel with the electric current suppressor; a determiner that determines whether or not the class-D amplifier is in a state where sound is not emitted; and a controller. When the determiner determines that the class-D amplifier is in a state where sound is not emitted, the controller turns off the switch such that a path for electric current flowing from the power source to the push-pull circuit runs through the electric current suppressor. When the determiner determines that the class-D amplifier is in a state where sound is emitted, the controller turns on the switch such that the path for electric current bypasses the electric current suppressor.

One or more embodiments relate to a multi-bias mode current conveyor. Such a current conveyor may include an input terminal, a reference terminal, an output terminal, a first and second cascoded current mirrors, and a biasing circuit. The first cascoded current mirror and a second cascoded current mirror may be arranged as a current conveyor that is configured to provide an output current that a mirror of an input current. The biasing circuit may be configured to provide a bias voltage selectively exhibiting a first voltage level or a second voltage level. The bias voltage may be provided at least partially responsive to a state of the input current. The biasing circuit may be arranged to apply the bias voltage to at least one of the first cascoded current mirror or the second cascoded current mirror.

A power transistor includes an ambient temperature input, a local temperature sensor, an array of transistor cells, and a thermal feedback circuit. The ambient temperature input is configured to receive an ambient temperature signal that is representative of an ambient temperature of the power transistor. The array of transistor cells has a control input. The local temperature sensor is configured to provide a local temperature signal that is representative of a temperature of the array of transistor cells. The thermal feedback circuit is coupled to the ambient temperature input, the local temperature sensor, and the control input. The thermal feedback circuit is configured to modulate a control signal provided at the control input based on a difference between the ambient temperature signal and the local temperature signal.

An amplifier includes a differential amplification block suitable for receiving and amplifying a first differential input signal and a second differential input signal; an output block suitable for determining an output signal according to a state of amplified signals outputted from the differential amplification block; and an output range restriction block suitable for controlling an output range of the output signal outputted from the output block based on a maximum clamping signal and a minimum clamping signal.

The disclosed technology relates to a method for improving performance of a feedback circuit comprising an amplifier and a feedback network, wherein the feedback circuit has at least one tunable component. In one aspect, the method comprises measuring first amplitude values at an input of the amplifier and second amplitude values at an output of the amplifier, estimating a linear open-loop gain of the amplifier based on both the amplitude values, estimating a linear finite gain error based on the estimated gain and the second amplitude values, subtracting the linear finite gain error from the first amplitude values to derive a set of samples containing second error information, deriving an signal-to-noise-plus-distortion ratio estimate based on the variance of the set of samples and a variance of the second amplitude values, and adjusting the feedback circuit in accordance with the signal-to-noise-plus-distortion ratio estimate.

A class-D amplifier that amplifies an input audio signal includes: a push-pull circuit that has at least two switching transistors; an electric current suppressor that is disposed between the push-pull circuit and a power source that supplies electric power to the push-pull circuit; a switch that is connected in parallel with the electric current suppressor; a determiner that determines whether or not the class-D amplifier is in a state where sound is not emitted; and a controller. When the determiner determines that the class-D amplifier is in a state where sound is not emitted, the controller turns off the switch such that a path for electric current flowing from the power source to the push-pull circuit runs through the electric current suppressor. When the determiner determines that the class-D amplifier is in a state where sound is emitted, the controller turns on the switch such that the path for electric current bypasses the electric current suppressor.

A bias circuit includes a replica circuit for an amplifier circuit using a cascode type inverter, and a generation circuit that generates a bias voltage that causes a drain voltage of an input stage transistor of the amplifier circuit to be a saturation drain voltage, based on an output voltage of the replica circuit, and supplies the generated bias voltage to a cascode element of the amplifier circuit and a cascode element of the replica circuit.

The present invention discloses a power amplifier capable of adaptively operating in one of an energy efficient mode and a high output power mode. An embodiment of the power amplifier includes a first transistor, a second transistor, a first bias element, a second bias element, a third bias element and a plurality of switches. In the energy efficient mode, by the control over the on/off states of the switches, an inverter type power amplifier is realized with the first transistor, the second transistor, the second bias element and the third bias element. In the high output power mode, by the control over the on/off states of the switches, a common source amplifier or a common emitter amplifier is realized with the second transistor and the first bias element.