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

In this paper, we report a novel CMOS circuit that is capable of maintaining constant heating power when the heater resistance varied. This kind of constant power heater circuit found application in various types of thermal base sensors, such as vacuum sensors, a.c. power meters, gas flow sensors and gas detection sensors. The circuit is designed so that the constant heating power is maintained when the heater resistance changes. The heating power is kept constant by controlling the reference current. The prototype is realized using the MOSIS 2µ OBIT n-well CMOS process. Experimental results showed that the heating power can be maintained to within 3% with ±50% variation in heater resistance.