Mos i/o protection using switched body circuit design

Abstract From the Canadian patent

Switched body circuitry is provided to prevent a system I/O from being effected by the loss of power supply or ground to an MOS integrated circuit within the system. A semiconductor substrate of a first conductivity type has formed therein a well region of a second conductivity type opposite to that of the first conductivity type. First, second, third and fourth spaced-apart shallow diffusion regions of the first conductivity type are formed at the surface of the well region. The first and fourth of these regions are electrically connected to the well region through ohmic contacts. A first gate electrode, which overlies a first channel region between the second diffusion region and the …