Scoposcopy: AC and DC Coupling: One Common Use
One common use of the AC coupling feature of oscilloscopes is to remove large DC offsets from a signal so that a much smaller time-varying (NOT true AC) signal can be displayed that may be “riding on top” of the large constant DC voltage level. Here I use the single-mosfet relay driver oscillator developed in the “MOSFETs How Do They Work” series to generate a set of signals of interest to use as examples. The HP180a scope’s AC coupling setting is selected to enable the amplification of the small changes in the Gate drive signal that ride on top of the larger 4 volt DC level as the relay is switched on and off by the rising and falling levels in the gate reservoir capacitor. Please see the MOSFETs series for the development of the test circuit. Thanks for watching !!