System and method for converging current with target current in device under test

A test system for measuring at least one parameter of a device under test (DUT) comprising a diode, the system comprising:

• a first voltage source unit connected to an anode of the diode and configured to supply a bias voltage to the anode, the first source unit comprising a voltage measurement device;
• a second voltage source unit connected to a cathode of the diode and comprising a current measurement device configured to detect a diode current flowing through the diode;
• a feedback unit configured to connect with the current measurement device and to output a feedback current during a feedback control operation based on the diode drain current;
• and
• an error amplifier configured to output a feedback control signal, based on comparison of the feedback current and a target current value, to the first voltage source unit,
• wherein the first voltage source unit is further configured to adjust the bias voltage of the transistor in response to the feedback control signal so that the diode current converges to match the target current value, and
• wherein the error amplifier includes a feedback gain based on the target current value and a coefficient, which is determined by a relationship between the bias voltage and the diode current.

A test system for measuring at least one parameter of a device under test (DUT) comprising a transistor, the system comprising:

• a first voltage source unit configured to supply a gate voltage to a gate of the transistor, the first source unit comprising a voltage measurement device;
• a second voltage source unit configured to supply one of a drain voltage or a source voltage to a drain or a source of the transistor, respectively, the second voltage source comprising a current measurement device configured to detect one of a drain current or a source current flowing through the drain or the source of the transistor, respectively;
• a feedback unit configured to connect with the current measurement device and to output a feedback current during a feedback control operation, based on the one of the drain current or the source current detected by the current measurement device;
• an error amplifier configured to output a feedback control signal to the first voltage source unit, the feedback control signal being based on a feedback gain of the error amplifier and on a comparison of the feedback current from the feedback unit and a target current value;
• a convergence determination device configured to monitor total feedback gain of the system based on measurements at different time points of the gate voltage and the one of the drain current or the source current, and to provide a corresponding transmission gain;
• and
• a controller configured to adjust the total feedback gain of the system in response to the transmission gain.