Patent ID: 7230444

Claim:
A field-effect-transistor characteristic measuring method in which a predetermined bias voltage output from an output terminal of a bias tee is applied to a drain of a field-effect transistor; a pulse output from a pulse generator is applied to a gate of the field-effect transistor to thereby cause drain current to be generated in the field-effect transistor; the drain current is converted into a voltage pulse by a load impedance connected to an alternating-current output terminal of the bias tee; and the drain current is measured based on the voltage pulse, the method comprising the steps of: increasing the bias voltage by an amount corresponding to a voltage drop caused by the load impedance and repeating measurement of the voltage pulse a predetermined number of times, while the voltage pulse changes in response to an increase in the bias voltage; and applying extrapolation to the last two measured values of the voltage pulse obtained by the predetermined number of repeated measurements to determine a drain voltage to be applied to the field-effect transistor.