Switched capacitor common-mode feedback structure

Abstract

The invention discloses a switched capacitor common-mode feedback structure and belongs to an analogue integrated circuit technique. The switched capacitor common-mode feedback structure comprises a common-mode detection switched capacitor circuit and an operational amplifier circuit, wherein the common-mode detection switched capacitor circuit is composed of four switches and four capacitors and is capable of amplifying a fully differential operational amplifier output swing, detecting a fully differential operational amplifier output common-mode voltage, and reducing influences of switch charge injection, clock feedthrough and capacitor initialized intrinsic charge on common-mode detection precision. A detected common-mode voltage and an ideal common-mode voltage are compared and amplified through an operational amplifier, then common-mode feedback current source bias voltage is output, the establishing time of the common-mode voltage can be effectively reduced, and the common-mode voltage precision is improved.

Description

technical field [0001] The invention belongs to the technical field of analog integrated circuits, and in particular relates to a common-mode feedback structure realized by using a switched capacitor and an operational amplifier. Background technique [0002] Due to the improvement of technology and the continuous improvement of design level, the development of integrated circuits is developing in the direction of high speed, high precision and low power consumption. In analog circuit design, a fully differential operational amplifier with a common-mode feedback structure is a commonly used basic circuit unit. [0003] Fully differential operational amplifiers with high output swing, fast stability, high precision and low power consumption 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 c...

AI Technical Summary

Problems solved by technology

[0013] In order to overcome the limitations of the output swing of the continuous-time common-mode feedback circuit and the shortcomings of the common-mode voltage establishment of the switched capacitor common-mode feedback circuit and the low precision of the common-mode voltage, the present invention proposes a common-mode feedback circuit realized by using a switched capacitor and an operational amplifier. Feedback structure, which uses a switched capacitor circuit to detect the output common-mode voltage, amplifies the common-mode error through the operational amplifier and feeds it back to the fully differential operational amplifier, which can effectively improve the output swing of the fully differential operational amplifier and reduce the establishment of common-mode voltage time, improving the accuracy of stable common-mode voltage

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