A mechanical-stress sensitive differential amplifier

A novel low power totally CMOS compatible mechanical-stress sensitive differential amplifier, which can be used as a pressure sensor, is presented. This amplifier is based on a special designed layout where the stress sensitivity of the input differential pair is maximized and the stress effects on the second stage are minimized. Finite element simulation was used to design the membrane and to locate the element sensor on it. The sensor was fabricated in a CMOS 0.35 μm process. In order to make a pressure sensor without a backside bulk micro-machining process, the thickness of the die was reduced by a mechanical polishing process. This paper also shows an automated structure used in the pressure sensors characterization. To reach a very well controlled pressure, the structure is totally controlled by LabView® Virtual Instruments. The sensor power consumption amounts to 3 μW and the sensitivity is adjustable by a convenient external feedback arrangement.