A low-power integrated circuit for interfacing a capacitive micromachined ultrasonic transducer (CMUT) based resonant gas sensor

In this work we present a complete end-to-end interface for a capacitive micromachined ultrasonic transducer (CMUT) intended for low-power gas sensing applications. A prototype chip was designed in a 0.18-μm BiCMOS process. Different blocks (a BJT-based Colpitts oscillator, an inverter-based oscillator, a sine-to-square wave converter, a digital frequency counter, and a parallel-to-serial converter) required for the complete system are discussed, designed, and tested for their standalone performance. Consequently, a complete system interfaced with a 3.6-MHz CMUT and providing a digital frequency output is presented. With duty cycling for one measurement per minute the system consumed 10 μW power.