Pixel circuit, electro-optical device, and electronic apparatus
A transistor circuit outputs a drive current in accordance with a data signal. An OLED that is connected to the transistor circuit emits light with luminance corresponding to the drive current. A discharge transistor, when the OLED does not emit the light, is turned on to connect a discharge feeder line to a node at which the transistor circuit is connected to the OLED. An absolute value of a threshold voltage of the discharge transistor is lower than an absolute value of a threshold voltage of a drive transistor in the transistor circuit. When the data signal indicates zero, the discharge transistor can cause a flow of the drive current from the transistor circuit to bypass the OLED.
1. A pixel circuit comprising:
a transistor circuit that outputs a drive current in accordance with a data signal, the transistor circuit including a drive transistor, a gate node of the drive transistor being supplied with the data signal;
a light emitting element that emits light with luminance corresponding to the drive current, the light emitting element being connected to the transistor circuit;
a discharge transistor that, when the data signal indicates zero, causes a flow of the drive current to bypass the light emitting element;
an off-state current generated in the discharge transistor in an off state;
a first leakage current output from the transistor circuit when the data signal indicates zero; and
a second leakage current of the discharge transistor, wherein:
a first channel length between a source of the discharge transistor and a drain of the discharge transistor is smaller than a second channel length between a source of the drive transistor and a drain of the drive transistor;
an absolute value of a threshold voltage of the discharge transistor is lower than an absolute value of a threshold voltage of the drive transistor; and
the off-state current is larger in amount than a sum of the first leakage current and the second leakage current.
2. The pixel circuit according to claim 1 , wherein:
the drive transistor in the transistor circuit generates the drive current in accordance with the data signal; and
when the light emitting element does not emit the light, the discharge transistor is turned on to connect a discharge feeder line to a node at which the transistor circuit is connected to the light emitting element.
3. An electro-optical device comprising the pixel circuit according to claim 2 .
4. The pixel circuit according to claim 1 , wherein
the drive transistor is a P-channel transistor, and the discharge transistor is an N-channel transistor.
5. The pixel circuit according to claim 4 , wherein:
the transistor circuit includes a light emission control transistor connected between the drive transistor and the light emitting element;
the light emission control transistor is a P-channel transistor; and
the drain of the discharge transistor has a wider area than a total area of a drain and a source of the light emission control transistor.
6. An electro-optical device comprising the pixel circuit according to claim 5 .
7. An electro-optical device comprising the pixel circuit according to claim 4 .
8. The pixel circuit according to claim 1 , wherein
the drain of the discharge transistor which is connected to the light emitting element has a wider area than an area of the source of the discharge transistor.
9. An electro-optical device comprising the pixel circuit according to claim 8 .
10. The pixel circuit according to claim 1 , wherein:
the drive transistor in the transistor circuit generates the drive current in accordance with the data signal;
when the light emitting element does not emit the light, the discharge transistor is turned on to connect a discharge feeder line to a node at which the transistor circuit is connected to the light emitting element; and
the drive transistor is an enhancement type transistor, and the discharge transistor is a depletion type transistor.
11. An electro-optical device comprising the pixel circuit according to claim 10 .
12. An electro-optical device comprising the pixel circuit according to claim 1 .
13. The pixel circuit according to claim 1 , wherein:
the drive transistor is a P-channel transistor, and the discharge transistor is an N-channel transistor; and
the drain of the discharge transistor which is connected to the light emitting element has a wider area than an area of the source of the discharge transistor.
14. A pixel circuit comprising:
a transistor circuit that outputs a drive current in accordance with a data signal, the transistor circuit including a drive transistor, a gate node of the drive transistor being supplied with the data signal;
a light emitting element that emits light with luminance corresponding to the drive current, the light emitting element being connected to the transistor circuit;
a discharge transistor that causes a flow of a part of the drive current in a light emission period;
an off-state current generated in the discharge transistor in an off state;
a first leakage current output from the transistor circuit when the data signal indicates zero; and
a second leakage current of the discharge transistor, wherein:
a first channel length between a source of the discharge transistor and a drain of the discharge transistor is smaller than a second channel length between a source of the drive transistor and a drain of the drive transistor;
an absolute value of a threshold voltage of the discharge transistor is lower than an absolute value of a threshold voltage of the drive transistor; and
the off-state current is larger in amount than a sum of the first leakage current and the second leakage current.
15. The pixel circuit according to claim 14 , wherein:
the drive transistor is a P-channel transistor, and the discharge transistor is an N-channel transistor; and
the drain of the discharge transistor which is connected to the light emitting element has a wider area than an area of the source of the discharge transistor.
16. A pixel circuit comprising:
a transistor circuit that outputs a drive current in accordance with a data signal, the transistor circuit including a drive transistor, a gate node of the drive transistor being supplied with the data signal;
a light emitting element that emits light with the luminance corresponding to drive current, the light emitting element being connected to the transistor circuit;
a discharge transistor that is turned off to cause a flow of the drive current;
an off-state current generated in the discharge transistor in the off state;
a first leakage current output from the transistor circuit when the data signal indicates zero; and
a second leakage current of the discharge transistor, wherein:
a first channel length between a source of the discharge transistor and a drain of the discharge transistor is smaller than a second channel length between a source of the drive transistor and a drain of the drive transistor;
an absolute value of a threshold voltage of the discharge transistor is lower than an absolute value of a threshold voltage of the drive transistor; and
the off-state current is larger in amount than a sum of the first leakage current and the second leakage current.
17. The pixel circuit according to claim 16 , wherein:
the drive transistor is a P-channel transistor, and the discharge transistor is an N-channel transistor; and
the drain of the discharge transistor which is connected to the light emitting element has a wider area than an area of the source of the discharge transistor.