A picosecond-response photoconductive-sampling probe for digital circuit testing

Recent efforts in noninvasive high-frequency and high-resolution measurement techniques have led to the development of a number of photoconductive probes. In this paper the feasibility of using the fiber-coupled, micromachined probe for in-circuit testing and characterization is demonstrated by detecting waveforms at internal nodes of two different digital circuits. On the one hand, measurements have been carried out which reveal the performance of a circuit under standard operating conditions. In this case the measured electrical signals originate from an external source, i.e., an rf synthesizer. In a second application, femtosecond optical pulses have illuminated one of the transistors of a circuit to generate the signal that is measured. This second approach is used to emulate so-called single-event upsets (SEU), which are usually caused by cosmic particles in satellite-based electronic systems. These effects have a negative impact on the performance and reliability of these systems and therefore are a limiting factor for their commercial implementation. In the past, optical techniques to generate SEU effects have been successfully demonstrated for testing single devices. In contrast, the results presented here demonstrate the generation and detection of these effects inside a complex circuit environment. Thus, they may especially benefit the development of radiation-immune circuits