Temperature compensated CMOS ring VCO for MEMS gas sensor

Abstract

This paper presents a CMOS voltage controlled ring oscillator with temperature compensation circuit suitable for low-cost and low-power gas sensor. To operate at low frequency, a control voltage generated by a CMOS bandgap reference is described and the measurement results of the fabricated chips are presented. The output voltage of the reference is set by resistive subdivision. In order to achieve small area and low power consumption, n-well resistors are used. This design features a reference voltage of 1 V. The chip is fabricated in AMS 0.35 μm CMOS process with an area of 0.032 mm2. Operating at 1.25 V, the output frequency is within 200 ± l0 kHz over the temperature range of −25 to 80 °C with a power consumption of 810 μW.