Patent ID: 7282943
Filing Date: 2007-10-16
Classification: G01R,H01L

Abstract:
1. An inspection device adapted to inspect a thin film transistor (TFT) for supplying a current to a light emitting element, said inspection device comprising: a first current supply circuit adapted to supply a drain current between a drain and a source of said TFT; a gate voltage adjustment circuit adapted to adjust a gate voltage to be applied to a gate of said TFT so as to allow a predetermined specified current to flow between said drain and said source of said TFT; a measurement unit adapted to measure said gate voltage adjusted by said gate voltage adjustment circuit; and a calculation unit operatively connected to said measurement unit and adapted to calculate a threshold voltage that is a threshold of a potential difference between said gate and said source of said TFT necessary to allow a current to flow between said drain and said source of said TFT based on the sequentially measured drain currents and a value β that is a parameter indicating a level of current supply between said drain and said source of said TFT, wherein when said drain current supplied by said first current supply circuit is larger, as determined by said gate voltage adjustment circuit, than said predetermined specified current, then said gate voltage adjustment circuit is adapted to adjust said gate voltage so as to reduce said drain current, and when said drain current supplied by said first current supply circuit is smaller than said predetermined specified current, then said gate voltage adjustment circuit is adapted to adjust said gate voltage so as to increase said drain current, wherein said first current supply circuit comprises: a voltage source having a predetermined potential; an electrical resistance operatively connected to said voltage source; and an output terminal operatively connected to said electrical resistance and adapted to supply a current to said TFT, wherein said predetermined potential of said voltage source and a resistance value of said electrical resistance are adjusted such that said first current supply circuit supplies said drain current when a potential of said output terminal is equal to a predetermined specified voltage, and wherein said gate voltage adjustment circuit comprises an amplifier adapted to receive inputs of said potential of said output terminal and said predetermined specified voltage and, when said potential of said output terminal is different from said predetermined specified voltage, said amplifier is adapted to apply a gate voltage to said TFT so as to make said potential of said output terminal equal to said predetermined specified voltage.