A low-supply-voltage CMOS sub-bandgap reference

A low-power (21 mu W) bandgap reference source that is operable from a nominal supply voltage of 1.4 V is described. The circuit provides an output voltage equal to the bandgap voltage having a low output resistance and allows resistive loading. It does not use resistors or operational amplifiers. Thus, the design is suitable for fabrication in any digital CMOS technology. The circuit uses a current conveyor and current mirrors to convert the proportional to absolute temperature voltage into a current using a MOSFET. The current is converted back to a voltage by using the functional inverse of the FET v - i characteristics. This makes the voltage gain linear and temperature independent. The absence of back-gate bias is the reason for achieving the low supply voltage of operation. Simulation results using the transistor models to the 0.18-mu m TSMC process show that the voltage-variation over the temperature range 0 to 100 degrees C is <1 mV.