Active feedback circuit for minimization of voltage transients during pulsed measurements of semiconductor devices

The operation of an active feedback circuit that minimizes voltage transients during pulsed-I-V measurements is presented. A field-effect transistor (FET) is used as the nominal device under test (DUT). The feedback circuit detects the sag in drain voltage that is caused by voltage drops produced across both the inductor in the drain bias tee and any series resistance in the drain-current path. The feedback signal consists of the current injected into the drain circuit that is sufficient to minimize the change in drain voltage. The feedback circuit actively synthesizes a small driving-point impedance that is seen by the drain of the DUT and is on the order of 10^-2 Ω. Larger voltages do not need to be applied to the drain circuit in order to overcome the nominal inductive and resistive voltage drops. Therefore, a low-current power supply can be used to set V_ds for low- or high-power FETs. Transient responses with and without the use of the feedback circuit are presented. Pulsed-I-V measurements using this feedback method (made less than 1 μs after the start of the gate pulse) of a high-power FET are also presented