Study And Design Of GAMMA Correction Circuit In AMOLED Driver Chip

In recent years,OLED technology has been a new favor of display panel manufacturers.The devices using this kind of technology have been popular all over the world with the advantages of lighter weight,thinner thickness,low power consumption and higher texture quality.GAMMA correction technology has decisive significance to the display effect of panel with adjustment of display curve and improvement of gray-scale voltage accuracy.In this thesis,a Gamma correction circuit suitable for driving AMOLED display panel with 1080*2220 resolution and 16.7 million colors is studied and designed.This thesis researched the structure and got the parameters of the VGMP/VGSP voltage generation circuit,VGMP/VGSP buffer circuit and breaking point output buffer circuit according to the fundamental principles of AMOLED driving theory.In order to keep the range of common mode input voltage from 0 to power supply voltage,VGMP/VGSP voltage generation circuit used the rail-to-rail input structure.The VGMP/VGSP buffer circuit used transconductance constant methodology to stabilize the output voltage for the high input swing.The breaking point buffer used class AB output stage to improve the load driving ability and cascode Miller compensation methodology to reduce the space occupation of the chip.Finally the layout design of GAMMA correction circuit is also accomplished.This thesis did the simulation verification of the whole module based on the technology of UMC 80 nm and got good performance with output voltage accuracy of 3m V and the total response time of 20 us.The VGMP/VGSP voltage generation circuit got the phase margin of 90 degree,55 d B loop gain and 13 us response time.VGMP/VGSP buffer circuit got the phase margin of 80 degree,60 d B loop gain and 1.446us/1.235 us response time.The breaking point buffer got the phase margin of 75 degree,129 d B loop gain and 1.49 us response time at 90% accuracy and 3.5us response time at 99% accuracy.The circuit can get expected performance according to the simulation result.The Post-simulation result of VGMP/VGSP output buffer agrees with the Pre-simulation result according to the simulation result.