A low-voltage power and area efficient BiCMOS log-domain filter

A 3rd-order Chebyshev filter based on the log-domain principle and integrated in a 1 µm BiCMOS process is presented. It has a nominal cut-off frequency of 320 kHz corresponding to a bias current of 1 µA and can be frequency tuned over almost 3 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 cut-off 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 mm²and 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.