Non-invasive internal testing of high speed microelectronics is essential for failure analysis and design verifications. This thesis presents electrostatic force sampling of high speed digital waveforms with the method of synchronous time domain gating to overcome the inherent bandwidth limitation. By inputting synchronized input signals into various low cost switches and gates, a proper probe signal can be generated to allow high speed digital sampling with the electrostatic force microscope. The performance of the proposed instrument using both modulation schemes is evaluated using theoretical characterizations and measurements on a ceramic transmission line, a passivated 0.5[mu]m CMOS inverter chain, and a NT25 pulse generator. Non-invasive extractions of up to 1'Gb'/' s' digital patterns are demonstrated with a voltage sensitivity in the range of tenths of millivolts and a delay accuracy of less than 10' ps'. The current bandwidth of the instrument is up to 3-4' GHz' which can be improved by the speed of the time domain gating circuitry. (Abstract shortened by UMI.)