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

The operation of an active, feedback circuit that minimizes voltage transie nts during pulsed-l-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 a cross both the inductor in the drain bias tee and any series resistance in the drain current path. The feedback signal consists of the current injecte d into the drain circuit that is sufficient to minimize the change in drain voltage. The feedback circuit actively synthesizes a small driving-point i mpedance that is seen by the drain of the DUT and is on the order of 10(-2) Ohm. Larger voltages do not need to be applied to the drain circuit in ord er 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 le ss than 1 mus after the start of the gate pulse) of a high-power FET are al so presented.