Current Mode Elliptic Filter Design Based on Symmertical Current Switching

Description/Abstract

This paper decribes a current-mode elliptic filter structure based on dual 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 symmertical current switching technique based on two switches controlled with a 2-bit digital word. The proposed filter structure forms a basic 2nd-order building block in the design of high-order elliptic filters with tunable frequency resposne. To confirm the theoretical analysis, simulated and measured results of 4th-order elliptic lowpass and highpass filters with tunable bandwidth in the range of 0.65MHz to 1.3MHz are included. Finally, detailed analysis of the OTA non-ideal parameters on the filter performance is presented and an example is given.