MOS-only voltage-mode all-pass filter core suitable for IC design

Abstract In this paper, an area efficient CMOS first-order voltage-mode (VM) all-pass filter (APF) is proposed. The introduced resistorless MOS-only core circuit consists of three transistors only. For the design three transconductances and one gate-to-source capacitance of MOS transistors are sufficient instead of external passive resistors and capacitors, while the full implementation of the VM APF consists of 12 MOS transistors and one grounded capacitor only. Hence, the proposed circuit exhibits important features such as simplicity, permitting reduced chip area when integrated and wide operating frequency range compared to classical analog counterparts that require active elements employing large number of transistors. The theoretical results are in detail verified by numerous post-layout simulations using Cadence IC6 Spectre analog design environment. In the design, medium Vth transistors with 1.8 V supply voltage were used and modeled by the TSMC 180 nm CMOS process parameters available in EUROPRACTICE IC Service design kit. The post-layout simulated pole frequency of the VM APF is 4.825 MHz, the implemented layout including metal-insulator-metal on-chip capacitor occupies an area of 31.1 μm × 39.5 μm, while the total power consumption of the filter is found to be only 92.57 μW.