A low power Gm-C filter with on-chip automatic tuning for a WLAN transceiver

A sixth-order Butterworth Gm-C low-pass filter(LPF)with a continuous tuning architecture has been implemented for a wireless LAN(WLAN)transceiver in 0.35 μm CMOS technology.An interior node scaling technique has been applied directly to the LPF to improve the dynamic range and the structure of the LPF has been optimized to reduce both the die size and the current consumption.Measurement results show that the filter has 77.5 dB dynamic range,16.3 ns group delay variation,better than 3% cutoff frequency accuracy,and 0 dBm passband IIP3.The whole LPF with the tuning circuit dissipates only 1.42 mA(5 MHz cutoff frequency)or 2.81 mA(10 MHz cutoff frequency)from 2.85 V supply voltage,and only occupies 0.175 mm2 die size.