Design of low frequency analog low pass filter using tunable pseudo resistors

This paper describes the use of tunable pseudo resistors in the design of analog low frequency low pass filters for implantable biomedical devices. Tunable pseudo resistors are MOSFETs biased in week inversion where large values of resistors can be achieved. Designs and circuit simulations of first, second and third order low pass filters with cut off frequency of 100 Hz are discussed. In addition, the paper describes the challenges related to linearity, noise and power consumption.