Abstract: A constantly conductive MOS transistor is placed in a logic circuit including a plurality of switching MOS transistors. The switching MOS transistors and the constantly conductive MOS transistor are connected in series and each receive a control signal at their respective gates. The constantly conductive transistor is in a conductive state regardless of the state of its control signal. Thus, it is difficult for a third party to learn the true logic structure of the logic circuit by visual inspection, as the third party will tend to recognize the constantly conductive transistor as a true transistor contributing to the logic circuit, and not as a constantly conductive "dummy" transistor.