A method and circuit arrangement for determining performance of a digital circuit to a critical degree by the transit time of signals of the longest signal path, also called the critical path. Since the signal transit time is influenced by the operating voltage, by regulating the operating voltage, to compensate for the effects caused by temperature and process fluctuations on the signal transit time in the digital circuit. In particular, the operating voltage can be regulated as a function of the signal transit time in such a way that a required minimum operating frequency can always be achieved. To determine signal transit time, the digital circuit has associated with it a number of replicas of the critical path in the digital circuit upon which the signal transit time is determined. In order to determine the transit time, the signal path replicas are exposed to the same operating conditions as the digital circuit. Also, to allow a safety margin to be obtained, the signal path replicas have additional circuit elements that further slow down the signal transit times on the signal path replicas. Further, the mean of the transit times on the signal path replicas is determined.