Switched capacitor common mode feedback structure

Abstract

The invention provides a switched capacitor common mode feedback structure, and belongs to the technical field of analog integrated circuits. The switched capacitor common mode feedback structure is applicable to a fully differential operational amplifier, and comprises an output level scaling switched capacitor module and a common mode level detection and amplification module, two input ends of the output level scaling switched capacitor module are connected with two output ends of the fully differential operational amplifier for scaling an output voltage of the fully differential operationalamplifier, so that the scaled voltage satisfies the input range of the common mode level detection and amplification module, an output end of the output level scaling switched capacitor module is connected with the input end of the common mode level detection and amplification module, the common mode level detection and amplification module detects the scaled voltage, and the output end of the common mode level detection and amplification module outputs a common mode feedback current source bias voltage to feed back a current source bias point of the fully differential operational amplifier,so that the output common mode level of the fully differential operational amplifier is stabilized at an ideal common mode level. The switched capacitor common mode feedback structure provided by theinvention not only has the advantages of higher speed and higher precision of the common mode feedback structure within a continuous time, but also has the advantages of large output amplitude and good linearity of the switched capacitor common mode feedback structure.

Description

technical field [0001] The invention belongs to the technical field of analog integrated circuits, and in particular relates to a switched capacitor common-mode feedback structure. Background technique [0002] The differential amplifier is one of the most important circuit inventions, dating back to the vacuum tube era. Because the differential amplifier has many useful characteristics, it has become the main choice of contemporary high-performance analog circuits and mixed-signal circuits, among which the fully differential operational amplifier with common-mode feedback structure is a commonly used basic circuit unit. [0003] Fully differential operational amplifiers with high output swing, fast stability and high precision are particularly important for the design of analog circuits, and the common-mode feedback structure directly affects the performance of fully differential operational amplifiers. The common-mode feedback structure can be divided into a continuous-ti...

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Problems solved by technology

[0012] Aiming at the disadvantages in the prior art that the output swing of the continuous-time common-mode feedback structure is limited, the common-mode voltage of the resistive load and the switched-capacitor common-mode feedback structure is slow to establish, and the switching noise is injected, the present invention proposes a switched-capacitor common-mode The feedback structure combines the switched capacitor common-mode feedback structure and the traditional continuous-time common-mode feedback structure. The voltage conversion of the output of the fully differential operational amplifier is scaled by the switched capacitor, so that the scaled voltage is within the input range of the rear-end common-mode detection circuit. , can effectively improve the output swing of the fully differential operational amplifier, reduce the common-mode voltage settling time, and improve the accuracy of the stable common-mode voltage

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