Based on the piezoresistive effect of MOSFET, a theoretical expression for stress-sensitive differential amplifier (SSDA) is founded, connecting the stress-induced carrier mobility variation and the output voltage of a SSDA. The HSPICE simulations are carried out and a method to increase SSDAs sensitivity is studied. The results show that both two input MOSFETs and two load MOSFETs of a SSDA can be used as stress sensing elements. (C) 2003 Elsevier Ltd. All rights reserved.