EMI control for VLSI biosensor circuitry

Design and fabrication techniques are presented which can be applied to improve the performance of biological processing devices in the presence of electromagnetic interference (EMI). A VLSI-compatible antialiasing filter was constructed and tested for application in an implanted medical device. The circuit consists of a continuous-time low-pass filter, a decimation filter, and a combined sample-and-hold and low-pass filter stage. The prefilter was implemented using a second-order Sallen-Key filter, although the chip version would substitute a passive first-order RC circuit. The frequency response of the combined filter stages is such that biosignals from DC to 150 Hz are within the passband while higher frequencies, including those caused by EMI, are rejected.<>