The present invention discloses a a process and temperature tracking bias circuits for realization of PT-invariant quantities in analog circuits. A proess and temperature tracing bias circuit is designed for making a constant resistance. On-chip resistances like RS- Nwel vareis by a factor of ± 20% at one particular temperature. The proposed bias technique which varies by ± 7.4% with process, 1.5% with temperature from 0°C to 100°C. resistance of a nmos transistor biased in linear region by a factor off 37% with process.