A Class-B Output Buffer for Flat-Panel-Display Column Driver

Abstract — Due to the large number of output buffers on a column driver chip of a flat-panel display, the quiescent current and die area of the output buffer must be minimized. This paper presents a low static power, large output swing, and wide operating voltage range class-B output buffer amplifier for driving the large column line capacitance in flat-panel display. A comparator is used in the negative feedback path to eliminate quiescent current in the output stage. The proposed output buffer circuit was implemented in a 0.8-m CMOS process. Its output voltage swing is from 1 V to the supply voltage. With 5-V supply and 600-pF load, the maximum tracking error is 7 mV. The measured static current is 24 A. The settling time for 4-V swing to within 0.2 % is 8 s, which is more than adequate for driving 1280 1024 pixels liquid crystal displays with 86-Hz frame rate and 256 gray levels in each color. Index Terms — Class-B amplifier, flat-panel display, output buffer