High Linearity Transconductance Amplifier Applied in Physiological Signal Filter

Abstract

The invention discloses a high-linearity transconductance amplifier applied in a physiological signal filter, comprising a differential input stage, a differential output load, a current offset transistor, a local negative feedback equivalent linear resistance, and a bias current transistor. The PMOS devices M1 and M2 form a differential output stage, and the signal is input from the bulk terminal; the NMOS devices M3 and M4 are used as the output load stage of the transconductance amplifier in the form of a current source, and the current offset transistor and the output pair have the same length and a certain width ratio Relationship, offset the drain current of the output pair tube, thereby reducing the transconductance; PMOS devices M12 and M13 form a local negative feedback equivalent linear resistance, and PMOS devices M9 and M10 are used to provide bias for the equivalent resistance. The present invention adopts the mode of body drive and current offset, on the one hand, it improves the linearity of the transconductance amplifier, and on the other hand, it reduces the transconductance value of the transconductance amplifier so that it is more suitable for being applied in the physiological signal filter.

Description

technical field [0001] The invention belongs to the field of transconductance amplifiers in integrated circuit design, in particular to a transconductance amplifier with high linearity applied to physiological signal filters. Background technique [0002] With the continuous development of biological and medical technology, it is necessary to amplify and filter the collected physiological signals such as EEG and ECG, and then convert them into digital signals through analog-to-digital conversion circuits for analysis and processing. In this process, filtering The filter plays a very important role, it needs to filter out the signal and noise outside the frequency band of interest, and only keep the useful physiological signal. [0003] There are many ways to realize the filter. Among them, the OTA-C architecture is widely used in low-frequency applications such as physiological signal filtering due to its low power consumption and small area. Compared with the switched capac...

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Problems solved by technology

[0004] For the filter of OTA-C architecture, its performance is mainly limited by the non-ideal characteristics of the transconductance amplifier, such as nonlinearity, noise, mismatch, process dispersion, etc., where the nonlinearity of the transconductance amplifier affects the performance of the filter The impact is the greatest, so it is extremely necessary to design a transconductance amplifier with high linearity. At present, the methods commonly used to improve the linearity of transconductance amplifiers, such as source negative feedback, adaptive bias, etc., have their insurmountable shortcomings. It affects its application range. For example, source negative feedback requires a large linear equivalent resistance, which will increase power consumption and area; adaptive bias will increase the complexity of the circuit due to the existence of feedback.

In addition, in order to reduce the on-chip capacitance, the transconductance of the transconductance amplifier needs to be as small as possible. Therefore, it is necessary to make it work in the weak inversion region, so that the power consumption will be reduced accordingly, but the performance is affected by device mismatch and process dispersion. will get bigger

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