A Low Ripple Switched Capacitor Common Mode Feedback Circuit

A switched capacitor circuit and common-mode feedback technology, applied in improving amplifiers to reduce temperature/power supply voltage changes, differential amplifiers, improving amplifiers to expand bandwidth, etc., can solve the problem of ripples in common-mode feedback output and the influence of fully differential operational amplifiers , the output cannot be stable and other issues, to achieve the effect of increasing the unity gain bandwidth, small ripple, and reducing the impact

Active Publication Date: 2018-05-08
SHENZHEN UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0011] The traditional switched capacitor feedback circuit is controlled by a discrete signal, and the calibration is performed every half clock cycle, so a certain settling time is required
Moreover, in the process of periodic charge and discharge, the output cannot be stabilized in formula (4)
That is, the common-mode feedback output has ripple and affects the fully differential op amp

Method used

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  • A Low Ripple Switched Capacitor Common Mode Feedback Circuit
  • A Low Ripple Switched Capacitor Common Mode Feedback Circuit
  • A Low Ripple Switched Capacitor Common Mode Feedback Circuit

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Embodiment Construction

[0030] The present invention provides a low-ripple switched capacitor common-mode feedback circuit. In order to make the purpose, technical solution and effect of the present invention more clear and definite, the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

[0031] see figure 2 , the low-ripple switched capacitor common-mode feedback circuit provided by the present invention includes a common-mode operation switched capacitor circuit 10 and a filter circuit 20, and the common-mode operation switched capacitor circuit 10 includes a first capacitor c1, a second capacitor c2, a third capacitor c3, fourth capacitor c4, first switch S1, second switch S2, third switch S3, fourth switch S4, fifth switch S5, sixth switch S6, seventh switch S7 and eighth switch...

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Abstract

The invention discloses a low-ripple switched-capacitor common-mode feedback structure. Two sets of MOS transistors which are connected into a diode are inserted between common-mode feedback output and a fully differential operational amplifier to achieve filtering of common-mode output signals, and therefore ripples of original output common-mode feedback signals are reduced. The low-ripple switched-capacitor common-mode feedback structure aims at reducing the voltage ripples of the feedback signals of a common-mode feedback circuit in the fully differential operational amplifier, the influences of small signals caused by clock feedthrough and capacitor charging and discharging on the fully differential operational amplifier are greatly reduced, and the output precision of the fully differential operational amplifier is improved. In addition, a traditional switched-capacitor common-mode feedback circuit needs a larger sampling capacitor, but in the low-ripple switched-capacitor common-mode feedback structure, the fewer ripples are achieved by using a smaller sampling capacitor, the load capacitor size is reduced, and the unity-gain bandwidth of the fully differential operational amplifier is increased.

Description

technical field [0001] The invention relates to the field of analog integrated circuits, in particular to a low-ripple switched capacitor common-mode feedback circuit. Background technique [0002] Switched capacitor common-mode feedback is a kind of feedback technology in analog integrated circuits, especially for high-performance fully differential operational amplifiers. Common-mode feedback is essential. It can stabilize the output common-mode level and reduce the operational amplifier Sensitivity to device characteristics and mismatch effects. Currently, there are two types of common-mode feedback implementations for fully differential operational amplifiers: continuous-time common-mode feedback and switched capacitor common-mode feedback circuits. The disadvantages of the former include affecting the differential output gain, poor differential mode load and extra power consumption. figure 1 Although the switch capacitor common-mode feedback shown overcomes the disadv...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H03F1/42H03F1/30H03F3/45
Inventor 邓小莺林鑫姜梅朱明程
Owner SHENZHEN UNIV
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