Nowadays, most electronic appliances have a display. In the display industry, liquid crystal displays (LCDs) are commonly used because they are cheap and the technology is rather mature and reliable. To drive a large capacitive LCD panel with many output levels, a few amplifiers connected as unity-gain buffers are used. The bias current may be increased to achieve an amplifier with a high slew rate, which would contradict with the performance requirement of portable applications where power consumption should be minimized. Hence, a slew rate enhancement (SRE) circuit that does not affect the linear operation of the core amplifier is needed....[ Read more ]

Nowadays, most electronic appliances have a display. In the display industry, liquid crystal displays (LCDs) are commonly used because they are cheap and the technology is rather mature and reliable. To drive a large capacitive LCD panel with many output levels, a few amplifiers connected as unity-gain buffers are used. The bias current may be increased to achieve an amplifier with a high slew rate, which would contradict with the performance requirement of portable applications where power consumption should be minimized. Hence, a slew rate enhancement (SRE) circuit that does not affect the linear operation of the core amplifier is needed.

This research presents an SRE circuit which do not affect the ac characteristic of the core amplifier. Compared to two other existing SRE schemes, the current comparison and the voltage comparison schemes, the proposed supply-independent current mode SRE circuit is more suitable for an LCD driver system, because it is less sensitive to input voltage swing, output loading change and power supply change. The small bias current is favorable for portable commercial products. The design is fabricated in a 0.35μm UMC CMOS process and occupies an area of 2644.8μm². A high voltage version is also implemented. The circuit performance is verified by measurement results.