Continuous-time Common-Mode Feedback Circuit for High-Speed ​​Fully Differential Operational Amplifiers

Abstract

The invention provides a CTCMFB circuit applied to a high-speed fully differential operational amplifier. The CTCMFB circuit comprises a common-mode voltage detection circuit, an error amplifier and a common-mode feedback control circuit, wherein the common-mode voltage detection circuit is used for detecting common-mode voltage output by the high-speed fully differential operational amplifier; the error amplifier is used for amplifying a comparison result of the common-mode voltage and expected common-mode voltage; the common-mode feedback control circuit is used for regulating the high-speed fully differential operational amplifier; the high-speed fully differential operational amplifier, the common-mode voltage detection circuit, the error amplifier and the common-mode feedback control circuit are mutually connected; and the error amplifier provides two channels of different output signals for the common-mode feedback control circuit so as to control the output common-mode voltage of the high-speed fully differential operational amplifier. The CTCMFB circuit applied to the high-speed fully differential operational amplifier has the advantages as follows: the structure is simple, the common-mode feedback loop gain is high, and the unity-gain bandwidth is large.

Description

technical field [0001] The invention relates to the field of integrated circuit design, in particular to a continuous-time common-mode feedback circuit applied to high-speed fully differential operational amplifiers. Background technique [0002] The high-speed fully differential operational amplifier has a high output swing and has a good suppression effect on common-mode interference such as environmental noise and power supply voltage noise, and has been widely used. In practical applications, a high-speed fully differential operational amplifier needs a common-mode feedback circuit to control the DC level of each node and output node inside the amplifier, so as to ensure that all transistors of the amplifier work in the saturation region, so that the amplifier can work normally and the output swing reaches best. [0003] The common-mode feedback circuit is a negative feedback circuit consisting of three parts: a common-mode voltage detection circuit, an error amplifier ...

AI Technical Summary

Problems solved by technology

In this common-mode feedback control circuit, the output common-mode voltage V OCM ’ and the desired output common-mode voltage V CM ’ is amplified by the error amplifier 3’ composed of M15’, M16’, M17’, M18’, M19’, due to the common-mode feedback voltage V cmfb0 'It is only obtained from the M16' and M18' branches of the differential amplifier, and the current of the other branch M15' and M17' is not used, which is wasted, resulting in low gain of the common-mode feedback loop and insufficient unity gain bandwidth; And in some high-speed differential operational amplifier applications, in order to ensure that the common-mode feedback circuit can quickly and effectively control the common-mode level, the bandwidth of the common-mode feedback circuit needs to be large enough, resulting in a large current consumption by the common-mode feedback

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