Current-mode elliptic filter design based on symmetrical current switching

Author: Dudek Frank   Al-Hashimi Bashir   Moniri Mansour  

Publisher: Taylor & Francis Ltd

ISSN: 1362-3060

Source: International Journal of Electronics, Vol.87, Iss.2, 2000-02, pp. : 163-175

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Abstract

This paper describes a current-mode elliptic filter structure based on dual-output OTAs and grounded capacitors. The filter is capable of producing both lowpass and highpass notch responses without changing the filter structure. This is achieved using a symmetrical current switching technique based on two switches controlled with a 2-bit digital word. The proposed filter structure forms a basic second-order building block in the design of high-order elliptic filters with tuneable frequency response. To confirm the theoretical analysis, simulated and measured results of fourth-order elliptic lowpass and highpass filters with tuneable bandwidth in the range of 0.65MHz to 1.3MHz are included. Finally, detailed analysis of the OTAs non-ideal parameters on the filter performance is presented and an example is given.