An active-Gm-RC continuous-time biquad low-pass cell

The design of an Active-G_m-RC biquad low-pass cell is presented. The cell combines the advantage of G_m-C filters (no parasitic poles) with the advantages of Active-RC filter (large linear range). As a prototype design, a second order low-pass filter with a pole frequency of 10MHz and a unitary Q factor has been designed in a 0.18μm CMOS technology with a 1.8V supply voltage. The cell shows an IIP3 of 30dBm at 1 MHz and an input referred noise of 30nV/√Hz while the power consumption is limited to 1.5mW only. The filter 3^rd parasitic pole is at 500MHz. A digital tuning scheme with a 1.5% accuracy has been adopted.