A compact low-power BiCMOS log-domain filter

A third-order Chebyshev filter based on the log-domain principle and integrated in a 1-μm BiCMOS process is presented. It has a nominal cutoff frequency of 320 kHz corresponding to a bias current of 1 μA, and can be frequency tuned over almost three decades up to about 10 MHz. It operates with a nominal supply voltage of 1.2 V, maintaining a dynamic range (DR) at 1% THD of 57 dB. For cutoff frequencies in the range of 10 kHz, the supply voltage can be reduced down to 0.9 V. The filter occupies an active area of 0.25 mm² and dissipates 23 μW, corresponding to a power consumption per pole and edge frequency of only 24 pJ. These results demonstrate the potential of log-domain filters for very low-voltage and low-power applications