A somewhat physical interpretation of can be found, if the effective carrier velocity used in the compact models for the transconductance is interpreted as bias dependent group velocity. then describes the phase information of this group velocity. This explains on one hand, why the absolute values of are in the order of magnitude of extracted delay times, on the other hand why a direct interpretation as the delay time of the device is not appropriate. On the other hand, typical delay times are extracted from the inverse of values for analog or from ring oscillators for digital applications.

2001-12-21