An improved sawtooth oscillator and its application in on-chip femto-ampere current monitoring

In the fathomable design of femto-ampere current mode circuit (FCMC), circuit for on-chip measurement and monitoring of femto-ampere current is in high demand, not only for its simplicity in structure and cheapness in price, but also for its high measure accuracy and process tolerance. In this paper, on-chip femto-ampere current monitoring methodologies based on improved sawtooth oscillator whose average leakage is as small as 3.844fA (at the room temperature of 27deg C) have been proposed and verified using SMIC models of 0.18mum CMOS process. Meanwhile, capacitance and leakage calibration techniques for high precision on-chip femto-ampere current monitoring are also characterized and discussed. According to the simulation results, on-chip monitoring of current ranging from 28.2fA to 10muA is achieved with relative deviations less than 10%