A 100µA Low Temperature Coefficient Current Reference with Composition of Subthreshold and Saturation Transistors

This paper presents a current reference circuit by employing the combination of the saturated and subthreshold transistors structures. At first, using these two structures PTAT and CTAT currents were generated and combined with together. Then to achieve low temperature variation coefficient, proper coefficients of the output currents of these two structures were combined leading to 100µA current reference. This current reference was post layout simulated in the 0.18μm CMOS TSMC technology with Cadence software and its layout size was 177.4μm×180.5μm. Post layout simulation results show that this current reference has a 3.68 ppm/°C variation in the temperature range of -40 to 120 Celsius degrees for TT transistors. In addition, its average temperature variation coefficient is 16.384 ppm/°C for 1000 iterations of Monte Carlo simulation. This circuit has a 2.9% sensitivity per one volt change of the supply voltage. This reference require to 396 millivolts headroom voltage to reach the 98% of the nominal current value. The power consumption of this circuit at the supply voltage of 1.8V was 39.67µW.