The ability to perform non-invasive high-frequency measurements at the internal points of an integrated circuit is important for the design and failure analysis of advanced microelectronics, As integrated circuit densities and speed increase, obtaining information on their internal operation becomes extremely difficult using conventional probing methods due to parasitic lending and low spatial resolution. We present a non-contact probing technique based on a nonlinear Coulomb force interaction for extracting high-frequency signals at internal points of an integrated circuit, Internal circuit voltages are measured by sensing the local electrostatic force on a small micromachined probe that is held in close proximity to the circuit measurement paint, The bandwidth of force measurements made using proximal probes are typically limited by the mechanical frequency response of the probe. In the presented instrument high frequency waveform measurements are enabled by using a pulse sampled heterodyne technique. The probing instrument has a bandwidth of 3 GHz and is capable of internal circuit delay measurements with a resolution of less than 10 ps. Measurement of the internal propagation delays and rise times of a complementary metal-oxide-semiconductor inverter chain are given.