A temperature and process insensitive CMOS reference current generator

This work presents a temperature and process insensitive CMOS transistor only reference current generator. In the proposed scheme, the passive resistor used in the CMOS Widlar current source is replaced with a transistor resistor where the gate voltage is controlled so that the output current is insensitive to temperature variation. Furthermore, to maintain the temperature insensitivity under process variations, the transistor resistor gate bias circuits optimized for nominal, strong and weak process corners are built on-chip. The proposed reference current generator is designed using 0.5 μm CMOS SOI technology, where the operation is verified through circuit level simulations under nine different process corners. The 20 μA reference current shows a temperature coefficient of 39 ppm/°C within the temperature range of 25°C ~ 125°C for the nominal process corner.