Design considerations of MOS-only allpass filters

In this paper, a simple filter topology that can be used to implement first-order MOS-only allpass filter is proposed. The proposed MOS-only allpass filter offers inherently very accurate magnitude and phase characteristics at very high frequencies. However, MOS-only active filter suffers from an inherent low frequency limitation. In order to address this issue, the modification technique allowing the derivation of MOS-only filter which allow extension of the operating frequency towards lower frequency region is proposed. Detailed simulations results of the filter modified according to the proposed technique are also provided in order to verify the usefulness of the theoretical approach.