There is provided an operational amplifier which is operable as well when an operating voltage decreases without creating a range where a circuit would not operate or reducing circuit gain. High-pass filters 102-105 provide output signals therefrom to bias-set input nodes of differential amplifiers Gm1-Gm4 to a potential within a common-mode range in which the respective differential amplifiers Gm1-Gm4 are operable. In this manner, the respective differential amplifiers Gm1-Gm4 can be operated effectively regardless of the possible decrease in a supply voltage, enabling normal amplifying operation. In addition, reduction in gain due to the reduced operational voltage is avoided. Therefore, it is preferably applicable to the application where digital and analog circuits are loaded together on the same IC chip. When a high-pass filter is required at each input side of two- or more-stage differential amplifiers, a phase compensation method utilizing multiple paths is provided for a lower range of a phase margin created at the low frequency side, enabling normal amplitude operation.

There is provided an operational amplifier which is operable as well when an operating voltage decreases without creating a range where a circuit would not operate or reducing circuit gain. High-pass filters 102-105 provide output signals therefrom to bias-set input nodes of differential amplifiers Gm1-Gm4 to a potential within a common-mode range in which the respective differential amplifiers Gm1-Gm4 are operable. In this manner, the respective differential amplifiers Gm1-Gm4 can be operated effectively regardless of the possible decrease in a supply voltage, enabling normal amplifying operation. In addition, reduction in gain due to the reduced operational voltage is avoided. Therefore, it is preferably applicable to the application where digital and analog circuits are loaded together on the same IC chip. When a high-pass filter is required at each input side of two- or more-stage differential amplifiers, a phase compensation method utilizing multiple paths is provided for a lower range of a phase margin created at the low frequency side, enabling normal amplitude operation.

A voltage reference buffer circuit, including: an amplifier having input terminals and output terminals; a plurality of current sources coupled to the input terminals of the amplifier, the plurality of current sources including a plurality of degeneration resistors coupled to a first plurality of voltage supplies; and a degeneration resistor chopping module comprising a first and second plurality of switches coupled to the plurality of degeneration resistors.

A circuit for generation of a reference voltage for an electronic system, which circuit comprises at least one digital buffer (U21, U31, U32, U41, U51), a low pass filter (R21, C21; R31, C31; R41, C41; R51, C51) and an operational amplifier (OA21, OA31, OA41, OA51)), which circuit is adapted to revive an input in the form of a bandgap reference voltage into the digital buffer, which digital buffer is adapted to receive a digital input from a Pulse Width Modulated (PWM) signal, which digital buffer is adapted to generate an output signal adapted to be fed to the low pass filter, which output signal after filtration is adapted to be fed to a positive input terminal of the operational amplifier, which operational amplifier comprises a feedback circuit, which feedback circuit comprises at least one capacitor (C22, C32, C44, C54) adapted to be connected from an output terminal of the operational amplifier towards a negative input terminal of the operational amplifier so as to form an integrator, wherein the feedback circuit further comprises at least one chopped signal path (R22, S21; R33, R34, S32; R33, R35, C35, S31), which chopped signal is adapted to be modulated by the output signal of the digital buffer.

A circuit for generation of a reference voltage for an electronic system, which circuit comprises at least one digital buffer (U21, U31, U32, U41, U51), a low pass filter (R21, C21; R31, C31; R41, C41; R51, C51) and an operational amplifier (OA21, OA31, OA41, OA51)), which circuit is adapted to revive an input in the form of a bandgap reference voltage into the digital buffer, which digital buffer is adapted to receive a digital input from a Pulse Width Modulated (PWM) signal, which digital buffer is adapted to generate an output signal adapted to be fed to the low pass filter, which output signal after filtration is adapted to be fed to a positive input terminal of the operational amplifier, which operational amplifier comprises a feedback circuit, which feedback circuit comprises at least one capacitor (C22, C32, C44, C54) adapted to be connected from an output terminal of the operational amplifier towards a negative input terminal of the operational amplifier so as to form an integrator, wherein the feedback circuit further comprises at least one chopped signal path (R22, S21; R33, R34, S32; R33, R35, C35, S31), which chopped signal is adapted to be modulated by the output signal of the digital buffer.

A signal amplifying circuit with noise suppression function includes a first circuit module and a second circuit module. The first circuit module includes a current source and a switch. The current source is connected to an input stage for inputting a current. The switch is connected to a first output terminal and adapted to switch the input stage and the first output terminal according to a chopping frequency. The second circuit module includes an equivalent capacitance disposed between an output stage and a second input terminal connected to the first output terminal. The signal amplifying circuit controls current volume of the current source and capacity value of the equivalent capacitance to accordingly adjust an interior frequency bandwidth of the signal amplifying circuit, and the interior frequency bandwidth is smaller than the chopping frequency and greater than an input signal of the input stage.

An instrumentation amplifier can include: an input port configured to receive a sensor signal; a first-stage amplifier configured to amplify the sensor signal to obtain a first intermediate signal; a first high-pass filter circuit, having input terminals coupled to output terminals of the first-stage amplifier, and being configured to eliminate a signal that is in the first intermediate signal and associated with an offset voltage of the first-stage amplifier, in order to obtain a second intermediate signal; a first chopper, having input terminals coupled to output terminals of the first high-pass filter circuit, and being configured to perform chopper modulation and demodulation on the second intermediate signal to obtain a third intermediate signal; and a second-stage amplifier, having input terminals coupled to output terminals of the first chopper, and being configured to amplify the third intermediate signal to generate an output signal.

An instrumentation amplifier can include: an input port configured to receive a sensor signal; a first-stage amplifier configured to amplify the sensor signal to obtain a first intermediate signal; a first high-pass filter circuit, having input terminals coupled to output terminals of the first-stage amplifier, and being configured to eliminate a signal that is in the first intermediate signal and associated with an offset voltage of the first-stage amplifier, in order to obtain a second intermediate signal; a first chopper, having input terminals coupled to output terminals of the first high-pass filter circuit, and being configured to perform chopper modulation and demodulation on the second intermediate signal to obtain a third intermediate signal; and a second-stage amplifier, having input terminals coupled to output terminals of the first chopper, and being configured to amplify the third intermediate signal to generate an output signal.

The present invention provides an amplifier including an input stage, an amplifier stage, a power stage and a de-gain stage. The input stage is configured to receive an input signal to generate an amplified signal. The amplifier stage is configured to generate a first driving signal and a second driving signal according to the amplified signal. The power stage comprises a first input terminal and a second input terminal, wherein the power stage is coupled to a supply voltage and a ground voltage, for receiving the first driving signal and the second driving signal from the first input terminal and the second input terminal, respectively, and generating an output signal.

The present invention provides an amplifier including an input stage, an amplifier stage, a power stage and a de-gain stage. The input stage is configured to receive an input signal to generate an amplified signal. The amplifier stage is configured to generate a first driving signal and a second driving signal according to the amplified signal. The power stage comprises a first input terminal and a second input terminal, wherein the power stage is coupled to a supply voltage and a ground voltage, for receiving the first driving signal and the second driving signal from the first input terminal and the second input terminal, respectively, and generating an output signal.