Inspection device for inspecting tft

An inspection device adapted to inspect a thin film transistor (TFT) for supplying a current to a light emitting element, wherein said TFT is adapted to operate in any of (i) a linear region where a drain current varies substantially linearly with voltages between a drain and a source of said TFT, and (ii) a saturation region where said drain current varies less than in said linear region, wherein said source of said TFT comprises a potential difference of an unknown and variable magnitude from a ground potential, wherein said inspection device comprises:

• a current supply circuit adapted to supply a drain current between said drain and said source of said TFT by applying a drain voltage to said drain of said TFT;
• a gate voltage application circuit adapted to apply a predetermined gate voltage to a gate of said TFT;
• a drain current adjustment circuit adapted to adjust said drain current supplied by said current supply circuit so as to make a potential difference between said gate voltage and said drain voltage become a preset set potential and so as to cause said TFT to operate in said linear region;
• a measurement unit adapted to sequentially measure said drain current adjusted by said drain current adjustment circuit for at least two different set potentials;
• 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.

An inspection device adapted to inspect a thin film transistor (TFT) for supplying a current to a light emitting element, wherein said TFT is adapted to operate in any of (i) a linear region where a drain current varies substantially linearly with voltages between a drain and a source of said TFT, and (ii) a saturation region where said drain current varies less than in said linear region, wherein said source of said TFT comprises a potential difference of an unknown and variable magnitude from a ground potential, wherein said inspection device comprises:

• a potential difference retaining circuit adapted to maintain such a potential difference so as to cause said TFT to operate in said linear region between a gate voltage to be applied to a gate of said TFT and a drain voltage to be applied to said drain of said TFT;
• a current supply circuit adapted to supply a drain current between said drain and said source of said TFT by applying said drain voltage to said drain of said TFT;
• a drain voltage adjustment circuit adapted to adjust said drain voltage so as to allow a preset set current to flow between said drain and said source of said TFT;
• a measurement unit adapted to cause said drain voltage adjustment circuit to sequentially adjust said drain voltage so as to allow at least two different set currents to flow, wherein said measurement unit is adapted to sequentially measure said gate voltage when said drain voltage is adjusted;
• 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 gate voltages, drain currents calculated based on gate voltages, and a value β that is a parameter indicating a level of current supply between said drain and said source of said TFT.

An inspection device adapted to inspect a thin film transistor (TFT) for supplying a current to a light emitting element, wherein one of a drain and a source of said TFT comprises a potential difference of an unknown magnitude from a ground potential, wherein said TFT is adapted to operate in (i) a linear region where a drain current varies substantially linearly with voltages between said drain and said source of said TFT, and (ii) a saturation region where said drain current varies less than in said linear region, and wherein said inspection device comprises:

• a gate voltage application circuit adapted to apply a gate voltage to a gate of said TFT;
• a drain voltage application circuit adapted to apply between said drain and said source such a voltage so as to cause said TFT to operate in said saturation region;
• a measurement unit adapted to measure a drain current flowing between said drain and said source of said TFT for each of at least two gate voltages applied by said gate voltage application 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 measured drain current and a value β that is a parameter indicating a level of current supply between said drain and said source of said TFT.