A resistance-variation-tolerant constant-power heating circuit for integrated sensor applications

We report a novel CMOS circuit that is capable of maintaining constant heat ing power when heater resistance varies, This type of constant-power heater circuit finds application in various types of thermal-based sensors, such as vacuum sensors, ac power meters, gas-flow sensors, and gas-detection sen sors. The heating power is kept constant by controlling a reference current , The circuit uses a bipolar-like translinear loop. To our knowledge, this is the first reported translinear loop implemented in CMOS, The prototype i s implemented using a MOSIS 2-mu m ORBIT n-well CMOS process. Experimental results showed that the heating power can be maintained to 3% with +/-50% v ariation in resistance when the heater resistance is 1 K Ohm. The maximum r ecorded heating power is about 11 mW for R-load of 1 K Ohm.