The effect of operating frequency on propagation delay in silicon-on-sapphire digital integrated circuits

The propagation delay between any two nodes in a silicon-on-sapphire MOS digital integrated circuit operating at supply voltages near transistor threshold has been observed to be a function of the operating frequency. This effect is attributed to a transient drain current whose magnitude decreases with increasing frequency of applied gate voltage. Evidence of this relationship is discussed as well as possible explanations for the origin of the transient current.