VLSI Design of a 5th-order Gm-C Low-Pass Active Filter in CMOS Technology

In this paper a VLSI design of a 5th order differential Gm-C low-pass active filter in CMOS technology and for different approximations is presented. The circuit architecture includes a first order Gm-C structure, two biquad-type structures and grounded capacitors. In order to increase the output swing, the active element used in the filter structure is based on a fully differential folded-cascode operational transconductance amplifier. The cutoff frequency of the proposed filter can be tuned through an external DC bias current around the 27 MHz frequency. The paper presents the complete design of a 5th order differential Gm-C low-pass active filter from the electric schematic to the layout implementation in a 0.18 µm CMOS technology. The pre-layout and post-layout simulations confirm the theoretical results.