Ultra Low Current (pA and below) Source & Measurement for Scientific Instrumentation
The present trend in semiconductor devices is towards low cost and low power consumption with better operating speed and functions. To address this trend the circuits and the systems are been designed in deep sub micron technologies with ultra low supply voltages. So it is always necessary to measure and source the currents at fempto level and voltages at pico level, but the presently available digital multi meters (DMMs) are generally adequate for measurements at signal levels greater than 1μV or 1μA, or less than 1G Ωohm. For low level signals, more sensitive instruments such as electrometers, fempto-ammeters, must be used. At such a low level measurements the potential error sources like offset voltages, noise and common-mode current, reversal errors and leakage currents will have serious impact on accuracy of the meters Among all the flicker noise become an important part of DC measurements and also generation of such a low level current requires very high resistances which introduces mismatches in sourcing because of its temperature and process variations. In this project we are proposing three different methods for pico ampere current sourcing and also aiming to study the different error sources at such low level measurements, to design and develop the fempto-ammeters and pico voltmeters considering noise effects and finally to measure and suppress the flicker noise in DC measurements.