Patent ID: 8456338

Claim:
A source-measure unit (SMU) comprising: output terminals configured to couple the SMU to a device, and further configured to convey an analog output signal to the device, to effect: an output current flowing into the device; and an output voltage across input terminals of the device; and a digital loop controller configured to: receive a first digital value representative of the output current and a second digital value representative of the output voltage; selectively regulate for one of the output voltage and the output current; when selected to regulate for the output current: adjust the analog output signal according to the first digital value to keep the output current at a specified current setpoint, until the output voltage reaches a specified voltage compliance limit; and adjust the analog output signal according to the second digital value to keep the output voltage from moving past the specified voltage compliance limit once the output voltage reaches the specified voltage compliance limit; when selected to regulate for the output voltage: adjust the analog output signal according to the second digital value to keep the output voltage at a specified voltage setpoint, until the output current reaches a specified current compliance limit; and adjust the analog output signal according to the first digital value to keep the output current from moving past the specified current compliance limit once the output current reaches the specified current compliance limit.