Analytical synthesis of current-mode even-Nth-order single-ended-input OTA and equal-capacitor elliptic filter structure with the minimum components

A current-mode "even"-nth-order OTA-C elliptic filter with the minimum components is presented in this paper. The filter, designed by the analytical synthesis method, is the counterpart of the recently reported current-mode "odd"-nth-order filter and features both current-mode signals and the important criteria of single ended input OTAs and grounded capacitors. Only (3n)/2 single-value and single-ended-input OTAs and n grounded capacitors, the minimum active and passive components, are used for the realization of this even-nth-order elliptic filter which is able to realize both highpass and lowpass transfer functions. The odd-nth-order filter is not applicable to highpass filtering. An equal-capacitance-type structure is designed taking account of the difficulty of precisely fabricating capacitances in integrated circuits. For the structure realized in this paper, simultaneously satisfying three criteria reduces the total inner parasitics to the minimum and produces more precise output response. H-spice highpass and lowpass simulations with 0.35mum process are shown for the proof of the theory