A novel, low voltage, precision CMOS current reference with no external components

A novel current reference with low temperature and supply sensitivity and without any external component has been developed in a 0.25 m mixed-mode process. The circuit is based on a bandgap reference (BGR) voltage and a CMOS circuit similar to a beta multiplier. An NMOS transistor in triode region has been used in place of a resistor in conventional beta multiplier to achieve a current which has a negative temperature coefficient and only oxide thickness dependent. The BGR voltage has a positive temperature coefficient to cancel the negative temperature coefficient of the beta multiplier. The simulation results using Bsim3v3 model show max-to-min fluctuation of less than 1% over a temperature range of 20 C to +100 C and a supply voltage range of 1.4 V to 3 V with 30% tolerance for all of the used on-chip resistors. The maximum current variation is slightly less than the oxide thickness variation in the process corners.