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.

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.

The present invention provides a circuit including a reference voltage generator and a plurality of receivers, wherein the reference voltage generator is configured to generate a reference voltage, and each of the receivers is configured to receive the reference voltage and a corresponding input signal to generate a corresponding output signal. In addition, for at least a specific receiver of the plurality of receivers, the specific receiver comprises at least one amplifying stage, the amplifying stage comprises a first input terminal configured to receive the corresponding input signal, a second input terminal configured to receive the reference voltage, a first output terminal configured to generate a first signal, and a second output terminal configured to generate a second signal; and the specific receiver further comprises a first feedback circuit coupled between the first output terminal and the second input terminal.

A circuit includes an analog-to-digital converter (ADC). The circuit also includes an analog front end (AFE) having an AFE input and an AFE output. The AFE output is coupled the ADC's input. The AFE includes a programmable gain amplifier (PGA) having a first PGA input and a second PGA input. The PGA includes a first operational amplifier (OP AMP) with first and second OPAMP inputs. The AFE also including a programmable resistance circuit having a first programmable resistance circuit input and first and second programmable resistance circuit outputs. The first programmable resistance circuit input is coupled to the first and second PGA inputs. The programmable resistance circuit includes a resistor network having first and second balance resistances. The first balance resistance is coupled to the first and second OP AMP inputs, and the second balance resistance is coupled to the first and second OP AMP inputs.

An apparatus measures a speaker impedance. A DAC converts a known digital input signal to an audio frequency first analog voltage signal. Resistors with known resistance attenuate the first analog voltage signal to generate a current. The known resistance effectively determines the current because the known resistance is high relative to the speaker impedance. The current is sourced into the speaker to generate a second analog voltage signal. The known resistance is sufficiently high to cause the second analog voltage signal to be inaudible as transduced by the speaker. An amplifier amplifies the second analog voltage signal with a known gain to generate a third analog voltage signal. An ADC converts the third analog voltage signal to a digital output signal. A processing element calculates the impedance of the speaker proportional to the digital output signal based on the known digital input signal, the known resistance, and the known gain.

According to one embodiment, a semiconductor integrated circuit includes first and second power supply lines, first and second nodes, and first and second circuits. The first circuit is configured to supply a first current to the second power supply line, from the first node or the second node. The second circuit is configured to supply a second current from the first power supply line to the first node based on a magnitude of the first current, and to supply a third current from the first power supply line to the second node based on the magnitude of the first current.

Disclosed is a differential amplifier including an input circuit, a detecting and controlling circuit, and an output circuit. The input circuit outputs input current to two output nodes according to the voltage of a differential input signal and the voltage of a bias node. The detecting and controlling circuit outputs compensative current to the two output nodes according to control bias voltage and the voltage of the bias node, in which the voltage of the bias node and the compensative current relate to the voltage of the differential input signal. The output circuit is coupled to the two output nodes and outputs a differential output signal according to the sum of the input current and the compensative current. Due to the detecting and controlling circuit outputting the compensative current, the differential amplifier prevents itself from entering a deadlock state even though the input current is insufficient or zero.

Disclosed herein is a circuit including a differential amplifier having a pair of input transistors coupled in a differential arrangement between adjustable current sources and receiving input differential signals from a pair of input voltage regulators. The adjustable current sources are configured to source more current to the pair of input transistors than current that is sunk from the pair of input transistors. A first amplifier has inputs coupled to receive differential output voltages from the differential amplifier. A second amplifier has inputs coupled to receive amplified differential output voltages from the first amplifier. A low pass filter has inputs coupled to receive further amplified differential output voltages from the second amplifier and produce final differential output voltages.

An analog discrete current mode negative feedback amplifier circuit for use with a micro-fused strain gauge is disclosed. The amplifier circuit includes a Wheatstone bridge coupled to a first power supply and a second power supply. The first power supply and the second power supply can be configured such that the periodically alternate between two voltage levels. The Wheatstone bridge can be coupled to a negative feedback amplifier circuit with common mode detection. The amplifier circuit can comprise a differential amplifier with a negative feedback configuration coupled to a common mode amplifier. In addition, the output of each of the amplifiers can be coupled to a common-mode amplifier. In a pressure sensing application, the output of the common mode amplifier serves to output the temperature while the differential amplifiers serve to output the pressure.

An automatic gain control circuit includes a linear-to-log conversion circuit, a current amplifier circuit, and an amplitude sense circuit. The current amplifier circuit includes a current input terminal coupled to an output terminal of the linear-to-log conversion circuit. The amplitude sense circuit includes an input terminal coupled to an output terminal of the current amplifier circuit, and an output terminal coupled to a gain control input terminal of the current amplifier circuit.