Low Noise Elliptical Filter in 250 Nanometer Technology for EEG Signals

A low noise filter for low frequency is presented. 5th order elliptical Filter design using OTA-C method is low in noise and good to acquire biopotential signal in range of 40 Hz. Filter provides strong attenuation against power line interference which occurs due to power supply of a system. For achieving low noise and low transconductance, current division and current cancellation technique (CDCC) is applied.

Filters also have a total harmonic distortion of 1.6 % with 50 millivolt peak to peak signals. OTA used CDCC topology provide the low transconductance required for low frequency application. OTA work in sub threshold region with bias current of 300 Nano amperes and also have a tuning ability with vtune voltage and it is biased with simple current mirror. This entire circuit design in 250 nanometer technology with 2.5 volt power supply using T-SPICE simulator of tanner EDA 15. Bandwidth and noise of a filter is 38 Hz, 3.36µvolt/ respectively.