High‐speed column‐line driving with polarity switch‐embedded output buffer amplifiers for TFT‐LCD application

Abstract

A novel high-speed column-line driving scheme having output buffer amplifiers embedded with polarity multiplexer switches is proposed for use in large-sized thin-film transistor liquid-crystal displays. The proposed driving scheme does not have explicit output-polarity switches, resulting in lower settling time. Experimental results in a 1.2 μm 13.5 V CMOS process indicated that using the proposed driving scheme the settling times to reach 99% of target voltages for the dot and column inversions were improved by up to 48.6%. This driving scheme can be applied to class AB-or class B-type amplifiers for liquid-crystal display column drivers and output buffers controlled by output switches.

High-Speed Column Driver IC Having Buffer Amplifier with Embedded Isolation Switch and Compact Adaptive Biasing for Flat-Panel Displays

“…The OP-MUXs are located at the rear of the buffer amplifiers. In [23], to avoid the ON-resistance of the OPMUXs, they have been embedded into the output stages of the buffer amplifiers. By this approach, the settling time can be improved but requires so many additional transistors (as many as 14), resulting in an area overhead.…”

“…Moreover, the dot inversion method typically requires explicit components such as polarity multiplexer switches to alternate the LC polarity, which can degrade the panel driving speed. Actually, in the FPD column driver, the time for panel driving is critical since it must not exceed the horizontal scanning pattern time [19][20][21][22][23][24][25][26].…”

“…To satisfy these requirements, class AB or B amplifiers [18][19][20][21][22][23][24][25][26] have been widely used as output buffer amplifiers in FPDs. In this case, there can be numerous issues concerning explicit switch on-resistance, high-slew-rate amplifier design, adaptive biasing circuit design, and the resulting overheads in terms of area and power consumption.…”

“…In this case, the settling time of the buffer amplifier increases due to the ON-resistance of these switches. To overcome this problem [23], proposed a driving scheme using embedded polarity multiplexer switches instead of explicit polarity multiplexer switches. In this scheme, the settling time can be enhanced but requires so many transistors for embedding the switches, resulting in an area increase.…”

“…The buffer amplifier with comparator structure consumes a lot of static current in static driving such as the black (TV) or white (Note-PC) pattern of an FPD. For the buffer amplifiers in [23][24][25], the class AB or B configuration has its slew-rate proportional to the bias current at the input. Thus, the power consumption increases as the bias current increases to provide a higher slew-rate.…”