Organic Light-Emitting Diode-on-Silicon Pixel Circuit Using the Source Follower Structure with Active Load for Microdisplays

Abstract

In this paper, we propose a pixel circuit immune to the electrical characteristic variation of organic light-emitting diodes (OLEDs) for organic light-emitting diode-on-silicon (OLEDoS) microdisplays with a 0.4 inch video graphics array (VGA) resolution and a 6-bit gray scale. The proposed pixel circuit is implemented using five p-channel metal oxide semiconductor field-effect transistors (MOSFETs) and one storage capacitor. The proposed pixel circuit has a source follower with a diode-connected transistor as an active load for improving the immunity against the electrical characteristic variation of OLEDs. The deviation in the measured emission current ranges from -0.165 to 0.212 least significant bit (LSB) among 11 samples while the anode voltage of OLED is 0 V. Also, the deviation in the measured emission current ranges from -0.262 to 0.272 LSB in pixel samples, while the anode voltage of OLED varies from 0 to 2.5 V owing to the electrical characteristic variation of OLEDs.

P‐53: A Novel Pixel Circuit Providing Expanded Input Voltage Range for OLEDoS Microdisplays

“…OLEDoS microdisplays are implemented on the single-crystalline silicon substrates using a standard complementary metal oxide semiconductor (CMOS) process. Therefore, the pixel blocks and the other control blocks such as gate driver, source driver, DC-DC converter, etc., can be integrated into a single chip of smaller than 1 inch [1][2][3][4][5][6][7][8][9][10][11][12][13][14].…”

“…Generally, two approaches were adopted to build the simple pixel circuits in previous works [7][8][9][10][11][12][13][14][15][16]. The first one is current programming.…”

Simple pixel circuits for high resolution and high image quality organic light emitting diode-on-silicon microdisplays with wide data voltage range

“…To solve the aforementioned problems, several OLEDoS pixel circuits have been proposed . Current programming pixel circuits compensate for the threshold voltage variation of the driving transistors, but are not suitable for high‐resolution display because the parasitic capacitance of the data line is too large to be programmed with a low gray‐level emission current of a few picoamperes .…”

“…To solve the aforementioned problems, several OLEDoS pixel circuits have been proposed. [5][6][7][8][9][10] Current programming pixel circuits compensate for the threshold voltage variation of the driving transistors, but are not suitable for highresolution display because the parasitic capacitance of the data line is too large to be programmed with a low gray-level emission current of a few picoamperes. [5][6][7] Voltage programming pixel circuits extend the data voltage range, but perform poor image quality due to the emission current deviation caused by the threshold voltage variation of the driving transistors.…”

“…[5][6][7] Voltage programming pixel circuits extend the data voltage range, but perform poor image quality due to the emission current deviation caused by the threshold voltage variation of the driving transistors. [8][9][10] In this paper, two simple pixel circuits A and B are proposed for high resolution and high image quality OLEDoS microdisplays, which can be implemented for a 0.8-in. full high-definition (FHD) OLEDoS microdisplays.…”