A mixed-mode on-chip automatic frequency tuning technique for biopotential amplifiers

This paper presents a mixed-mode on-chip automatic frequency tuning technique to achieve a process-invariant lowpass cut-off frequency for biopotential amplifiers. It comprises of a sine-like test signal generation circuit, a digital scheme to minimize the deviations in the frequency of the test signal, a programmable switched capacitor array acting as the load of the biopotential amplifier, and a peak detector based digital capacitor selection logic. Results obtained show that the proposed technique curtails the deviation of the cut-off frequency across process (and temperature) variations. The complete scheme implemented in UMC 0.18 \(\upmu\)m CMOS technology consumes only 1.02 \(\upmu\)W average power approximately with 1.8 V supply. Moreover the complete tuning mechanism lasts for less than half a minute only. Its low power consumption and implementation on analog platform makes it integrable with the standard portable biomedical systems intended for remote monitoring.