A thin-diaphragm piezoresistive pressure sensor for biomedical instrumentation has been developed using monolithic integratedcircuit (IC) techniques. The piezoresistive effect has been chosen for this device because it provides an observable resistance change that is a linear function of pressure and is observable at low stress levels. A diaphragm is used as a stress magnifying device; its magnification is proportional to the square of the ratio of the diaphragm diameter to its thickness. The pressure-induced stresses in the diaphragm are sensed by properly oriented piezoresistors interconnected to form a bridge.