Patent ID: 7444525

Claim:
An apparatus, comprising: at least one digital circuit implemented using a plurality of transistors in a silicon-on-insulator (SOI) arrangement, at least some of the transistors being referenced to a virtual ground node; at least one switch transistor coupled from the virtual ground node to a ground node for a power supply to the digital circuit; and a control circuit operable to: (i) enable the digital circuit by biasing the switch transistor ON such that a voltage potential of the virtual ground node is substantially equal to a voltage potential of the ground node; (ii) disable the digital circuit by biasing a gate terminal of the switch transistor below the voltage potential of the ground node such that the voltage potential of the virtual ground is substantially higher than the ground node; and (iii) control a substrate voltage of the SOI arrangement as a function of a threshold voltage of the at least one switch transistor.