CMOS input signal buffer applied to front end of high-speed ADC

Abstract

The invention belongs to the technical field of integrated circuits, and particularly relates to a CMOS input signal buffer applied to the front end of a high-speed ADC. The circuit structure comprises an input buffer with two differential source following structures, a common-mode feedback circuit module and a bias circuit module. According to the invention, stable common-mode output of a sourcefollower can be ensured; a channel length modulation effect under a deep submicron CMOS process is avoided; a N-type transistor adopts a deep N-well device to eliminate the substrate bias modulation effect. A cascode current source with large output impedance is used for providing bias current for an input transistor so as to relieve output signal nonlinearity caused by input signal changes. The buffer is used in an ADC circuit, can play a role in improving linearity and isolating an input signal from a post-stage circuit, has good linearity even when an input signal with higher frequency is input, and is particularly suitable for a front-end buffer circuit of a high-speed ADC.

Description

technical field [0001] The invention belongs to the technical field of integrated circuits, and in particular relates to a CMOS input signal buffer applied to the front end of a high-speed ADC. Background technique [0002] Analog-to-digital converter (ADC) is a bridge connecting the analog world and the digital world. Physical signals in nature such as force, temperature, light, sound, etc. are all analog signals. However, digital signal processing has higher reliability and Lower cost, so the analog signal needs to be converted to digital first. Therefore, the analog-to-digital converter is a key component in many analog-to-digital hybrid systems, and becomes one of the important factors restricting the performance of the entire system. With the gradual development of the fifth-generation wireless communication technology, various application scenarios such as the Internet of Everything and 5G communication micro base stations have brought new challenges to the design of ...

AI Technical Summary

Problems solved by technology

[0004] A common input signal buffer adopts an open-loop source follower structure. The source follower of the open-loop structure can obtain larger bandwidth, higher linearity, low output impedance, and larger signal drive capability. However, due to temperature And the change of the process angle, the output common mode level of the source follower of the open-loop structure will drift, resulting in the input common mode drift of the comparator, resulting in an error in the comparison result

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