Highly Sensitive CMUT with Built-in Low-Voltage FET

A novel structure of CMUT with a built-in low-voltage FET composing an impedance converter was proposed. The electrode opposing to the high-voltage electrode is divided into two electrodes: a central sensing and a peripheral ground electrode. The central electrode should work as an FET gate, whose voltage is directly modulated by the displacement of the membrane. The voltage sensitivity of the proposed CMUT was as high as a best-designed piezoelectric transducer. A nearly unity fractional bandwidth, a bandwidth significantly wider than a conventional CMUT, was achieved with a proper resister between the sensing electrode and ground.