A new technique for the measurement of speeds of gigahertz digital IC's

We describe a new technique for the measurement of picosecond switching speeds and propagation delays in gigahertz digital IC's. This technique, based on logic-level sampling with pairs of ultrashort optical pulses at variable interpulse delays, provides accurate and reliable values of picosecond propagation delays without requiring the coupling of high-frequency electrical signals to and from the IC chip. Since this optical technique dispenses with the usual need for dicing and mounting the IC wafer in high-frequency (multigigahertz bandwidth) test fixtures, a promising application of its use is in the precise temporal characterization of multigigabit logic circuits in low-frequency (< 100-MHz) probe stations.