Patent ID: 8653840

Claim:
A source-measure unit comprising: output terminals configured to couple the source measure unit to a device under test, and further configured to convey an analog output signal to the device under test to effect: an output current flowing into the device under test; and an output voltage in the device under test; a first converter configured to generate a first digital value representative of the output current; a second converter configured to generate a second digital value representative of the output voltage; and a digital loop controller configured to: receive the first digital value and the second digital value; generate a digital control signal based on the first digital value and the second digital value; determine based on the first digital value whether the output current is outside a specified measuring range; if it is determined that the output current is outside the specified measuring range, generate a digital override signal, and select one of the digital control signal and the digital override signal to obtain a selected digital signal used to adjust the analog output signal, wherein the selected digital signal effects a desired return of the output current into the specified measuring range.