On designing linearly-tunable ultra-low voltage CMOS gm-C filters

A linearly-tunable ULV transconductor featuring excellent stability of the processed signal common-mode voltage upon tuning, critical for very-low voltage applications, is presented. Its employment in the synthesis of CMOS g_m-C high-frequency and voiceband filters is discussed. SPICE data describe the filter characteristics. For a 1.3 V supply, their nominal passband frequencies are 1.0 MHz and 3.78 kHz, respectively, with tuning rates of 12.52 kHz/mV and 0.16 kHz/mV, input-referred noise spectral density of 1.3 μV/Hz^1/2 and 5.0 μV/Hz^1/2 and standby consumption of 0.87 mW and 11.8 μW. Large-signal distortion given by THD=1% corresponds to a differential output-swing of 360 mV_pp and 480 mV_pp, respectively. Common-mode voltage deviation is less than 4 mV over the tuning interval