A high value, linear and tunable CMOS pseudo resistor for bio-medical applications

A sub-threshold MOS based pseudo resistor featuring a very high value and ultra-low distortion is proposed. A band-pass neural amplifier with a very low high-pass cutoff frequency is designed, to demonstrate the linearity of the proposed resistor. A BJT less CTAT current generator has been introduced to minimize the temperature drift of the resistor and make tuning easier. The stand-alone resistor has achieved 0.5% better linearity and a 12% improved temperature coefficient over the existing architectures. A neural amplifier has been designed with the proposed resistor as a feedback element. It demonstrated 31dB mid-band gain and a lowpass cutoff frequency of 0.85Hz. The circuit operates from a 1V supply and draws 950nA current at room temperature.