MOS Integrated silicon pressure sensor

An MOS integrated silicon-diaphragm pressure sensor has been developed. It contains two piezoresistors in a half-bridge circuit, and a new simple signal-conditioning circuit with a single NMOS operational amplifier. The negative temperature coefficient of the pressure sensitivity at the half-bridge is compensated for by a positive coefficient of the variable-gain amplifier with a temperature-sensitive integrated feedback resistor. The sensor was fabricated using the standard IC process, except for the thin diaphragm formation using the N2H4. H2O anisotropic etchant. Tile silicon wafer was electrostatically adhered to the glass plate to minimize induced stress. The -1750 ppm/°C temperature coefficient of sensitivity at the half-bridge was compensated for to less than +190 ppm/°C at the amplifier output in the 0- 70°C range. A less than 20-mV thermal-output offset shift was also Obtained after 26-dB amplification in the same temperature range.