Methods and apparatus are provided for testing to determine the existence of defects and faults in circuits, devices, and systems such as digital integrated circuits, SRAM memory, mixed signal circuits, and the like. In particular, methods and apparatus are provided for detecting faults in circuits, devices, and systems using input control signals to generate controlled-duration, controlled pulse-width, transient power supply currents in a device under test, where said transient power supply currents are of controllable bandwidth and can be used as observables to determine faulty or defective operation. Additionally, methods and apparatus are provided to permit high bandwidth sensing of transient supply currents as need to preserve the narrow widths of these current pulses. These methods may include autozero techniques to remove supply current leakage current and DC offsets associated with practical current sensing currents. The sensed transient supply currents can be compared to single or multiple thresholds to assess normal or faulty or defective operation of the device under test.