Low-voltage high-common-mode-rejection amplifier

Abstract

The invention discloses a low-voltage high-common-mode-rejection amplifier. The low-voltage high-common-mode-rejection amplifier comprises a basic circuit constructed by connection of differential pair transistors and a common-mode rejection amplifying circuit, and is provided with a common-mode feedback circuit consisting of field-effect transistors P2B, P2C, N2B and N2C, and a current summing circuit consisting of field-effect transistors N3, N4, P6, P5, P3A and P3B; the field-effect transistors P2B and P2C of the common-mode feedback circuit and the field-effect transistor P2A of the common-mode rejection amplifying circuit are in common-gate connection with a common-gate reference voltage VCP; power supply end current sources P1A and P1B and ground end current sources N1A and N1B of the common-mode rejection amplifying circuit mirror current flowing through onto the field-effect transistor Nb through the current summing circuit; the field-effect transistor Nb and a resistor Rb are in common-mode matching with the field-effect transistor Na and a resistor Ra through which reference current IREF flows; and current flowing through the field-effect transistor N2A in the common-mode rejection amplifying circuit is clamped to be close to the reference current IREF. Through feedback automatic biasing in the amplifier, the common-mode rejection effect of the circuit is enhanced. Meanwhile, the amplifier can work under low supply voltage.

Description

technical field [0001] The invention relates to a common-mode suppression amplifier, in particular to a low-voltage high-common-mode suppression amplifier which can operate under low power supply voltage and whose output performance is not affected by input common-mode voltage changes, and belongs to the field of integrated electronic circuit design. Background technique [0002] Low supply voltage high common mode rejection amplifiers are widely used in high performance medical and industrial systems such as figure 1 The conventional operational amplifier shown has been widely used, so the description of its circuit structure is omitted. The advantage of this structure is that the rising and falling slew rate can be balanced, but the disadvantage is that the common gate current changes with the input common-mode voltage, which causes the offset voltage to change with the input common-mode voltage, and the output performance is difficult to meet practical needs. [0003] So...

AI Technical Summary

Problems solved by technology

This structure ensures the balance of the slew rate and can improve the common mode rejection of the circuit, but there is a diode series bias P 0B and P 3C , can not work under low supply voltage, amplifier application can not be expanded

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