A Temperature and Supply-Voltage Insensitive CMOS Current Reference

In this work, a CMOS on-chip current reference circuit for memory, operational amplifiers, comparators, and data converters is proposed. The reference current is nearly insensitive to temperature and supply-voltage variations. In the proposed circuit, the current component with a positive temperature coefficient cancels that with a negative temperature coefficient each other. While conventional current reference circuits are based on bipolar transistors in BiCMOS, bipolar, or CMOS processes, the proposed circuit can be integrated on a single chip with other digital and analog circuits using a standard CMOS process and extra masks are not required. Measured results are demonstrated for two different prototypes. The first is fabricated employing a 1.0μm p-well double-poly double-metal CMOS process and operates at 5V nominally. The second, based on a 0.6μm n-well process, is optimized for 3V to 5V operation. The latter prototype achieves the temperature coefficient of 98 ppm/◦C over a temperature range from −25◦C to 75◦C and the output variation of ±1.5% with the supply-voltage changes from 2.5V to 5.5V. A simple calibration technique for reducing output current variations improves circuit yield. key words: current reference, CMOS, low-cost, low-voltage,