COMPENSATION OF SENSITIVITY SHIFT IN PIEZORESISTIVE PRESSURE SENSORS USING LINEAR VOLTAGE EXCITATION

When the temperature increases, the output voltage from a silicon piezoresistive pressure sensor will decrease when the excitation voltage to the sensor element is kept constant. This is due to the temperature dependence of the piezoresistive effect. Compensation of this effect can be achieved by either increasing the voltage excitation or by increasing the amplification of the output signal from the sensor with increasing temperature. This article discusses the method of increasing the voltage excitation linearly with temperature. Analysis shows that the sensitivity shift can be reduced to less than 0.6% within the temperature range - 30 to + 100 degrees C if the excitation voltage has a proper temperature coefficient. This has been experimentally verified for two different sensor types. The first type uses thin-film deposited polysilicon resistances, and the second type uses diffused resistors. Without compensation the sensitivity shifts for the chosen sensor types are 7 and 16%, respectively in this temperature range.