Absolute potential measurements inside microwave digital IC's using a micromachined photoconductive sampling probe

A measurement system for internal node testing of integrated circuits using a micromachined photoconductive sampling probe is described and characteri zed, Special emphasis is placed upon the system performance, demonstrating how absolute voltage measurements are achieved in a dc-to-mm-wave bandwidth , The feasibility of the setup is illustrated using an InP heterojunction b ipolar transistor frequency divider. Detailed waveforms at different circui t nodes and the corresponding propagation delays from within this circuit a t operating frequencies up to 10 GHz are presented. The results demonstrate for the first time the use of photoconductive probes for calibration-free, absolute-voltage, de-coupled potential measurements in high-frequency and high-speed integrated circuits.