Active matrix type display apparatus and drive circuit thereof

A picture element drive circuit to be provided at each cross point of a data line for supplying a signal current having current level corresponding to an intensity information and a scanning line for supplying a selecting pulse and for driving a current drive type light emitting device which emits light by a drive current, comprising:

• an accept section for accepting said signal current from the corresponding data line in response to said selecting pulse from said scanning line;
• a converting section for converting thus accepted signal current once into corresponding voltage and restoring thus converted voltage;
• and
• a drive section for supplying the drive current having current level corresponding to the restored voltage to the corresponding light emitting device, and
• said converting section includes:
• a conversion thin film transistor having a gate electrode, a source electrode, a drain electrode and a channel;
• and
• a capacitor connected to said gate electrode of the conversion thin film transistor, wherein the conversion thin film transistor generates at the gate electrode the voltage converted by flowing through said channel the signal current taken through said accept section and said capacitor holds the voltage generated at the gate electrode of the conversion thin film transistor,
• said drive section contains:
• a drive thin film insulated gate type field effect transistor including a gate electrode, a drain electrode, a source electrode and a channel and the drive thin film insulated gate type field effect transistor, wherein the drive thin film insulated gate type field effect transistor supplies the drive current through the channel to the light emitting device and the drive current has the current level corresponding to the voltage restored in the capacitor and accepted at the gate electrode of the drive thin film insulated gate type field effect transistor, and
• a threshold voltage of said drive thin film insulated gate type field effect transistor is set not to become lower than a threshold voltage of said conversion thin film insulated gate type field effect transistor corresponding to the picture element.

A method for driving picture element to be provided at each cross point of a data line for supplying a signal current having a current level corresponding to an intensity information and a scanning line for supplying a selecting pulse and for driving a current drive type light emitting device which emits light by a drive current, comprising the steps of:

• step for accepting said signal current from the corresponding data line in response to said selecting pulse from corresponding scanning line;
• step for converting thus accepted signal current once into corresponding voltage and restoring the voltage;
• and
• step for driving by supplying the drive current having the current level corresponding to the restored voltage to the corresponding light emitting device, and
• said converting step includes:
• step for using a conversion thin film transistor having a gate electrode, a source electrode, a drain electrode and a channel;
• and a capacitor connected to said gate electrode of the conversion thin film transistor, wherein the conversion thin film transistor generates at the gate electrode the voltage converted by flowing through said channel the signal current taken through said accepting step and said capacitor holds the voltage generated at the gate electrode, said driving step includes:
• step for using a drive thin film insulated gate type field effect transistor having a gate electrode, a drain electrode, a source electrode and a channel, wherein said the drive thin film insulated gate type field effect transistor supplies the drive current through the channel to the light emitting device, wherein the drive current has the current level corresponding to the voltage stored in the capacitor and accepted at the gate electrode of the drive thin film insulated gate type field effect transistor, and
• a threshold voltage of said drive thin film insulated gate type field effect transistor is set not to become lower than a threshold voltage of said conversion thin film insulated gate type field effect transistor corresponding to the picture element.

An active matrix type display apparatus comprising:

• a scanning line drive circuit for sequentially selecting scanning lines;
• a data line drive circuit for sequentially supplying signal current corresponding to an intensity information to data lines;
• and
• a plurality of picture elements provided at each cross point of said “data line” and said scanning lines and each of the picture elements having a current drive type light emitting device which emits light in response to drive current corresponding to said signal current, wherein
• each of said picture element comprises:
• an input thin film transistor connected to said data line;
• a conversion thin film transistor connected to said input thin film transistor for converting said signal current on said data line to corresponding voltage;
• a switch thin film transistor connected between a gate electrode and a source electrode of said conversion thin film transistor;
• a capacitor connected to said gate electrode of said conversion thin film transistor for restoring said corresponding voltage;
• and
• a drive thin film transistor connected to said light emitting device and to aid capacitor, wherein
• a threshold voltage of said drive thin film transistor is set not to become lower than a threshold voltage of said conversion thin film transistor within one the picture element.