On the design of micro power practical GmC filters for biomedical applications

Transconductor-capacitor or simply GmC filters and amplifiers are an attractive option for the design of biomedical circuits because of their extremely low power consumption. GmC filters for the analog processing of sensed outputs and biomedical signals, can be realized consuming as little as a few tens or hundreds nA current (a negligible power budget for a primary battery). Minimum or no external components are required, but there is always uncertainty in the transfer function of the filter. This paper shows the development of fully integrated GmC filters for medical applications, emphasizing on the variability of their response with technology parameters that may change from an integrated circuit to another or from a fabrication batch to another. GmC filters, amplifiers and rectifiers will be presented. Two examples are discussed: a GmC band pass amplifier for a piezoelectric accelerometer to estimate physical activity and a robust GmC cardiac sensing channel.