Display apparatus with active matrix type display panel
A display apparatus which can display an image at a proper luminance corresponding to a video signal irrespective of a temperature-related change or a change with the passage of time. The display apparatus has: a current source for generating a reference current; and a reference transistor having an input terminal for a power voltage, an output terminal to which the current source is connected, and a control terminal connected to the output terminal and having almost the same electrical characteristics as those of a driving transistor for supplying a drive current to a light emitting device serving as a pixel. The driving transistor is driven by a voltage (reference control voltage) on the control terminal of the reference transistor. The loss of electric power can be suppressed by the driving method of this apparatus.
1. A display apparatus having a display panel in which light emitting units are arranged in a matrix each said light emitting units being constituted by a driving transistor for generating a drive current in accordance with a voltage applied to a control terminal thereof and a light emitting device for emitting light in accordance with said drive current, comprising:
a reference control voltage generating circuit which includes a series circuit connected between ground and a power voltage, said series circuit being constituted by a current source for generating a reference current and a reference transistor having an input terminal for said power voltage, an output terminal to which said current source is connected, and a control terminal connected to said output terminal and having electrical characteristics substantially identical to said driving transistor and which produces a voltage on said control terminal of said reference transistor as a reference control voltage; and
a data driver for supplying one of said power voltage and said reference control voltage to said control terminal of said driving transistor in accordance with pixel data of each pixel based on an input video signal,
wherein said power voltage or said reference control voltage produced by said reference control voltage generating circuit is selectively supplied to data lines of said matrix of said light emitting units through said data driver.
2. An apparatus according to claim 1 , wherein said reference transistor has a substantially identical specification as said driving transistor.
3. An apparatus according to claim 1 , wherein said current source generates a current corresponding to a panel luminance adjustment signal for adjusting a luminance level of said whole display panel, as said reference current.
4. An apparatus according to claim 1 , wherein said light emitting device is an electroluminescence device.
5. An apparatus according to claim 1 , wherein said current source of said reference control voltage generating circuit is a variable current source which generates said reference current according to a panel luminance adjusting signal.