A 550mV 8dBm IIP3 4pth order analog base band filter for WLAN receivers

In this paper a 4^th order low-pass continuous- time filter for a WLAN receiver is presented. The filter is designed to satisfy high-linearity performance while operating at very-low supply voltage. An improved bias circuit is used to operate with different opamp input and output common-mode voltages. The filter is realized in a standard 0.13 mum CMOS technology with V_THNap250 mV and V_THPap300 mV. The filter is optimally operating with supply voltage as low as 550 mV and slightly below. The filter architecture is composed by two active Gm-RC biquadratic cells, which use a single opamp per-cell with a unity-gain-bandwidth comparable to the filter cut-off frequency. This reduces the total cell power consumption. The -3 dB frequency is at 12 MHz (for WLAN applications) and this is higher than any other low-voltage continuous-time filter. The -3 dB frequency can be adjusted by means of a digitally- controlled capacitance array. The filter total area occupancy is 0.47 mm² and the total power consumption is 3.4 mW from a single 550 mV supply. A 8 dBm-in-band IIP3 and a 13.3 dBm-out-of-band IIP3 demonstrate the validity of the proposal.