Focused Test, Inc manufactures the FTI 1000 test system for DC and AC characterization and production test of power discrete devices. FTI 1000 performs AC tests such as Gate Charge (Qg) test using an AC channel board as part of our â€˜Tester-per-Boardâ€™ system architecture. The Gate Charge test method uses an on-board Pulse Generator to supply a constant current Gate ramp and an on-board Digitizer to capture the Gate voltage. A software algorithm detects the Qgs and Qgd inflection points and datalogs the Gate Charge values. We have developed a proprietary calibration method to eliminate the parasitic parameters of the test fixture and device package to enable accurate Qgs and Qgd measurements on devices with sub-1nC Gate Charge. To illustrate this, consider a high voltage discrete device with 1pF Gate to Drain capacitance. At 500V operation this results in a Qgd of 500pC. Our Qg calibration method ensures that the total parasitic capacitance is reduced to less than 1pF to enable accurate Qgd measurement.