Display Driver Buffer Circuit Reducing Miller Effect
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Solution Overview
Problem
Display drivers face challenges in achieving high refresh rates due to delays in rising and falling input voltages of source amplifiers, primarily caused by significant effective input capacitances, which are exacerbated by the Miller effect.
Innovation Solution
Incorporating a buffer with an NMOS transistor and a PMOS transistor between the digital-to-analog converter (DAC) and the source amplifier, where the NMOS transistor acts as a pull-up and the PMOS transistor as a pull-down, to reduce effective input capacitance and minimize the Miller effect, thereby accelerating the rising and falling of input voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a source amplifier is designed to drive source lines at high refresh rates, then the display performance is improved, but the effective input capacitance causes delays in rising and falling input voltages
Solution Approach 1:
A buffer circuit is introduced as an intermediary component between the DAC and the source amplifier. This buffer includes a PMOS transistor and an NMOS transistor that act as mediators to drive the input terminal of the source amplifier, thereby reducing the delay caused by the effective input capacitance and enabling high refresh rates without sacrificing voltage transition speed.
2Speed
If the effective input capacitance of the source amplifier is reduced, then the rising and falling of input voltages is accelerated, but the Miller effect exacerbates the delay
Solution Approach 1:
The buffer circuit serves as an intermediary that isolates the source amplifier's input capacitance from the DAC output. The PMOS and NMOS transistors in the buffer actively drive the input terminal, counteracting the Miller effect by providing low-impedance driving capability that prevents voltage delays despite the presence of high input capacitance.
Data Source
AI summary
A display driver comprises a digital-to-analog converter (DAC) configured to output a grayscale voltage corresponding to an image data. The display driver further comprises a source amplifier configured to drive a source line of a display panel, and a buffer connected between the DAC and the source amplifier. The buffer comprises a first NMOS transistor having a gate supplied with the grayscale voltage and a drain connected to a power supply. The buffer is configured to supply a current depending on a first current flowing through the first NMOS transistor to an input terminal of the source amplifier.