Pixel circuit for an active matrix OLED display
A circuit arrangement for organic light-emitting diodes can be arranged in a two-dimensional matrix. It can in particular be used with microdisplays. It can allow a wide influencing of the brightness of the electromagnetic radiation emitted by the organic light-emitting diodes. Every organic light-emitting diode can be controlled by means of a storage circuit, a sense amplifier and a driver circuit using the circuit arrangement. The driver circuit can be formed by at least three transistors connected in series and a further output transistor whose drain is connected to the anode of the respective organic light-emitting diode. In this respect, the transistor acting as the driver can have a constant electric operating voltage LVDD applied at its source and a further likewise constant electric operating voltage V drive is applied to its gate. The drain of the first transistor to the source of the following transistor connected to it in series and the two gates of the following transistors which form a switch and are connected in series are connected to the output of the sense amplifier and are acted on by its electric output voltage V SenseOut . The drains of the two transistors forming the switch are connected to the source of the output transistor whose gate is connected to ground potential or to which negative electric voltage is applied.
1. A circuit arrangement for organic light-emitting diodes arranged in a two-dimensional matrix in which every organic light-emitting diode can be controlled, the circuit arrangement comprising:
a storage circuit, a sense amplifier and a driver circuit,
wherein the driver circuit includes at least first, second, and third transistors connected in series and a further output transistor whose drain is connected to an anode of a respective organic light-emitting diode and whose gate is connected to a ground potential or to which negative electric voltage is applied and in this respect the first transistor acting as a driver is acted on by a constant electric operating voltage LVDD at its source and by a further likewise constant electric operating voltage V Drive at its gate; with a drain of the first transistor being connected to a source of the following second transistor connected in series to it and the two gates of the second and third transistors forming a switch being connected to the output of the sense amplifier and being acted on by its electric output voltage V senseout ; and
the drain of the second transistor forming the switch being connected to the source of the output transistor whose gate is connected to ground potential or to which negative electric voltage is applied,
wherein the second transistor which is connected at its source to the first transistor acting as a driver is a PMOS transistor and the third transistor whose gate is connected with the gate of the second transistor together to the output of the sense amplifier is an NMOS transistor, and
wherein a source of the third transistor and a gate of the output transistor being connected to the same ground potential or to which the same negative electric voltage is applied.
2. The circuit arrangement in accordance with claim 1 , wherein all elements of the circuit arrangement are formed as a CMOS circuit on a semiconductive substrate.
3. The circuit arrangement in accordance with claim 1 , wherein a further transistor is arranged between the first transistor acting as a driver and the second transistor, connected in series, to switch off the driver circuit.
4. The circuit arrangement in accordance with claim 3 , wherein the further transistor is a PMOS transistor.
5. The circuit arrangement in accordance with claim 1 , wherein an electric voltage is applied to the cathode of the organic light-emitting diode which is smaller than the electric voltage which is applied to the source of the third transistor and to the gate of the output transistor connected to the anode of the organic light-emitting diode.
6. The circuit arrangement in accordance with claim 1 , wherein the gate of the first transistor acting as a driver is connected to ground potential and this first transistor forms a switch of the driver circuit.