An error amplifier circuit receives first and second input signals and provides an error amplifier output signal indicative of the difference between the first and second input signals. The error amplifier circuit implements a proportional-integrator-differentiator (PID) circuit having a differential input signal path and including a proportional amplifier circuit, an integrator amplifier circuit, and a differentiator amplifier circuit. The differentiator amplifier circuit receives an AC coupled input signal. The error amplifier circuit sums the output from the proportional amplifier circuit, the integrator amplifier circuit and the differentiator amplifier circuit to provide the error amplifier output signal where the error amplifier output signal is referenced to a first bias voltage.

An operational amplifier includes a single-stage amplifier and a current controller. The single-stage amplifier receives an input signal, and amplifies the input signal to generate an output signal, wherein the single-stage amplifier includes a voltage controlled current source circuit that operates in response to a bias voltage input. The current controller receives the input signal, and generates the bias voltage input according to the input signal. The bias voltage input includes a first bias voltage, a second bias voltage, a third bias voltage, and a fourth bias voltage. None of the first bias voltage, the second bias voltage, the third bias voltage, and the fourth bias voltage is directly set by the input signal of the single-stage amplifier.

Various examples are directed to a frequency-compensated amplifier circuit comprising a first multi-stage amplifier comprising a first amplifier input node, a first amplifier output node, and a first amplifier intermediate node. A first feedback path between the first amplifier input node and the first amplifier output node comprises a feedback resistance. A second feedback path between the first amplifier output node and the first amplifier intermediate node comprises a first capacitor and a portion of the feedback resistance. A first switch circuit may be electrically coupled to the first capacitor and to the feedback resistance. The first switch circuit may have a first state in which the first capacitor is coupled to a first tap point of the feedback resistance and the portion of the feedback resistance has a first value. The first switch circuit may also have a second state in which the first capacitor is coupled to a second tap point of the feedback resistance and the portion of the feedback resistance has a second value different than the first value.

The present disclosure provides an audio amplifying circuit and a playing device, including: N-order filters and an integrated circuit; after an original audio signal passes through the N-order filters, a filtered signal is obtained; after the filtered signal passes through the integrated circuit, a corresponding digital signal is output; where the number of operational amplifiers adopted in the N-order filters is smaller than N, and N is a natural number greater than 1.

A system for testing a subject transistor with constant power. The system may include an amplifier, a measurement voltage source, and a exercise voltage source. The amplifier may have an output connected to a gate of the subject transistor. The amplifier may have a first input and a second input. The measurement voltage source may be connected to the first input of the amplifier for use in measuring characteristics of the subject transistor. The exercise voltage source may be connected to the first input of the amplifier for exercising the subject transistor. The second input of the amplifier may be connected to a source of the subject transistor through a resistor.

The semiconductor device includes a Hall element, a first differential pair, a second differential pair, an output amplifier circuit, and a voltage divider circuit. The Hall element outputs a signal that is dependent on stress to be applied to a semiconductor substrate to the first differential pair. The voltage divider circuit divides a voltage into a divided voltage having a voltage dividing ratio that is dependent on the stress. The first differential pair outputs a first current based on the signal. The second differential pair outputs a second current based on the divided voltage and a reference voltage. The output amplifier circuit outputs a voltage based on the first and second currents. A gain of the output amplifier circuit is approximated by a sum of a difference between stress dependence coefficients of transconductances of the first and second differential pairs and a stress dependence coefficient of the voltage dividing ratio.

Various examples are directed to amplifier circuits and methods for operating amplifier circuits. The amplifier circuit may comprise a first amplifier stage. The first amplifier stage comprises a first amplifier, a first feedback resistance, a second amplifier, a second feedback resistance, and a gain resistance. A first current source may be electrically coupled to provide a first current across the gain resistance in a first direction. A second current source may be electrically coupled to provide a second current across the gain resistance in a second direction opposite to the first direction.

A circuital system that includes a differential low-pass filter having a differential output and operable in a first voltage domain. Some embodiments include a differential integrator including a differential input and a differential output, and operable in a second voltage domain different from the first voltage domain. Some embodiments include a pair of AC coupling capacitors coupling the differential output of the differential low-pass filter to the differential input of the differential integrator.

A single-ended analog signal receiver apparatus is provided, which can cope with an external ground current and an undefined impedance through an AC bootstrap input impedance, while considering electromagnetic compatibility, convert a received single-ended analog signal into a balanced output differential signal, and may provide at a post-stage circuit output an output signal with lower noise through common mode rejection.

A two-stage differential amplifier with cross-coupled compensation capacitors. The differential amplifier includes first amplifier circuitry receiving a differential input voltage and presenting first and second intermediate outputs. The amplifier further includes a second amplifier stage with a first leg having an input coupled to the second intermediate output of the first amplifier circuitry, and a second leg having an input coupled to the first intermediate output of the first amplifier circuitry. A compensation capacitor is provided for each leg of the second amplifier stage, each coupled between the output of that amplifier leg and its input. A first cross-coupled capacitor is coupled between the output of the first amplifier leg to the input of the second amplifier leg, and a second cross-coupled capacitor is coupled between the output of the second amplifier leg and the input of the first amplifier leg.