Four-order current type elliptical filter structure based on OTA-C

Abstract

The invention belongs to the field of integrated circuit design, and relates to a four-order current type elliptical filter structure based on OTA-C. The filter is composed of four grounding capacitors and six single-ended input OTA, and comprises two current signal input ends Iin and a current signal output end I'out. From the perspective of mathematical derivation, an analytical synthesis method is adopted, and poles of the four-order current type elliptic filter are determined through a transfer function. And the frequency characteristic of the circuit can be changed only by changing various coefficient values of a circuit transfer function without changing the circuit topology, so that four filtering functions of low-pass, high-pass, band-pass and band-stop are realized respectively. As the OTA can adjust the transconductance value through the external bias current, the elliptical filter designed by the invention has good in-band selectivity and also can realize adjustable functions.

Description

technical field [0001] The invention belongs to the field of integrated circuit design, and in particular relates to an OTA-C-based fourth-order current type elliptic filter structure. Background technique [0002] In bioelectrical signal processing technology, filter is a very important module. The frequency of human bioelectrical signals is extremely low, and the frequency ranges of various signals overlap, such as ECG (0.05Hz-150Hz), EEG (0Hz-150Hz), EGG (0.05Hz-0.5Hz), ERG (0Hz-20Hz) etc., the selectivity requirements of the filter are very strict. Nowadays, electronic equipment tends to be miniaturized, how to realize highly selective and miniaturized filters is a current research hotspot. [0003] There are roughly three types of active filters in analog integrated circuits: RC filters, MOSFET-C filters and OTA-C filters. Due to the extremely low frequency of bioelectrical signals, a large RC is required and the absolute error of passive components is large, so that...

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Problems solved by technology

[0006] The existing bioelectrical signal filter structure has the following disadvantages: (1) It is necessary to change the circuit topology to realize the functions of low-pass, high-pass, band-pass and band-stop filters; (2) the energy consumption of the voltage mode circuit is large, and the working Speed ​​is limited; (3) electronically adjustable or poorly tunable; (4) in-band selectivity is not good enough; (5) the design method is complex and the number of components is too large

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