Pixel circuit, display apparatus, and pixel circuit drive control method
A pixel circuit including a light emitting element, a driving transistor, connected to the light emitting element, that applies a drive current to the light emitting element, a holding circuit connected to a gate terminal of the driving transistor, and a switching transistor connected between the holding circuit and a data line through which a data signal to be held by the holding circuit flows, in which the driving transistor and the switching transistor are inorganic oxide thin film transistors whose OFF-operation threshold voltage is a negative voltage, and the holding circuit includes a first capacitor element connected between the switching transistor and the gate terminal of the driving transistor, and a second capacitor element connected between a point located between the first capacitor element and the gate terminal of the driving transistor and a voltage source that supplies a negative voltage.
1. A pixel circuit comprising:
a light emitting element,
a driving transistor, connected to the light emitting element, that applies a drive current to the light emitting element,
a holding circuit connected to a gate terminal of the driving transistor, and
a switching transistor connected between the holding circuit and a data line through which a data signal to be held by the holding circuit flows, wherein:
the driving transistor and the switching transistor are inorganic oxide thin film transistors whose OFF-operation threshold voltage is a negative voltage; and
the holding circuit includes a first capacitor element connected between the switching transistor and the gate terminal of the driving transistor, and a second capacitor element connected between a point located between the first capacitor element and the gate terminal of the driving transistor and a voltage source that supplies a negative voltage.
2. A display apparatus, comprising
an active matrix substrate on which a pixel circuit is disposed in a large number, the pixel circuit comprising:
a light emitting element,
a driving transistor, connected to the light emitting element, that applies a drive current to the light emitting element,
a holding circuit connected to a gate terminal of the driving transistor, and
a switching transistor connected between the holding circuit and a data line through which a data signal to be held by the holding circuit flows, wherein:
the driving transistor and the switching transistor are inorganic oxide thin film transistors whose OFF-operation threshold voltage is a negative voltage; and
the holding circuit includes a first capacitor element connected between the switching transistor and the gate terminal of the driving transistor, and a second capacitor element connected between a point located between the first capacitor element and the gate terminal of the driving transistor and a voltage source that supplies a negative voltage;
a scan drive circuit that supplies to each switching transistor a scanning signal for turning ON/OFF each switching transistor; and
a data drive circuit that supplies the data signal to be held by the holding circuit,
wherein the scan drive circuit is a circuit that supplies a positive voltage as the scanning signal and the data drive circuit is a circuit that supplies a positive voltage as the data signal.
3. The display apparatus as claimed in claim 2 , the negative voltage VB supplied to the second capacitor element, a capacitance C 1 of the first capacitor element, a capacitance C 2 of the second capacitor element, and the threshold voltage VTH satisfy the relationship of Formula (1) below, and a minimum setting value V datamin of the data signal, an OFF scan signal V scan(off) , and the threshold voltage VTH satisfy the relationship of Formula (2) below,
VB ≦(1+2 ×C 2 /C 1)× VTH (1)
V datamin ≧V scan(off) −VTH (2).