Abstract: The low frequency notch filter integrated circuit is implemented in a relatively small silicon area and with high linearity, thereby promoting the utilization of very large-scale integration (VLSI) techniques in biomedical instrumentation. The filter circuit utilizes R-2R ladders providing area saving of approximately 120:1. R-2R ladders function as digitally programmable resistors in a biquad configured Operational Amplifier filter circuit. Integrator loop topologies are used in the filter circuit. The preferred topology utilizes a Tow-Thomas circuit, which can be designed for the prerequisite gain and Q independently selecting two resistors. In addition, the three op amps in the Tow-Thomas topology have their non-inverting input grounded, and therefore their inverting inputs will be held ideally at virtual ground. These feature permits the use of op amps with small common mode input range.