Patent ID: 7126596

Claim:
A line-inversion LCD display driver, comprising: a source driver suitable for switching one of a plurality of drive voltages to a column of LCD pixels in response to a digital code word, the transparency of each of said pixels varying over a predetermined pixel voltage range, each of said pixels receiving said selected drive voltage at its first terminal and alternately switched between first and second voltages at its second terminal, said source driver comprising a plurality of resistors connected in series and having accessible connection points at each end of said series string and at various resistor—resistor junctions along said series string, said series string producing at least some of said drive voltages when said connection points are connected to respective correction voltages, and a grayscale reference generator circuit, comprising: a plurality of voltage sources, each of which is arranged to output a respective correction voltage, an interface circuit interposed between said voltage sources and said connection points, comprising: a plurality of amplifiers, each of said amplifiers comprising: an input which is coupled to first and second ones of said correction voltages, said first correction voltage closer to said negative supply rail than said positive supply rail and said second correction voltage closer to said positive supply rail than said negative supply rail, positive and negative supply rails, a p-type differential transistor pair, a first switchable current source connected to supply tail current to said p-type differential pair when enabled in response to a first control signal, said p-type differential pair connected to provide a first differential output current when said tail current is supplied which varies with a differential input signal applied to said p-type pair's control inputs, an n-type differential transistor pair, a second switchable tail current source connected to supply tail current to said n-type differential pair when enabled in response to a second control signal, said n-type differential pair connected to provide a second differential output current when said tail current is supplied which varies with a differential input signal applied to said n-type pair's control inputs, an output stage which receives said first and second differential output currents and is arranged to produce an output voltage at an output terminal which varies with said first and second differential output currents, said output terminal being said amplifier's output, and a control circuit which provides said first and second control signals such that said first switchable current source is enabled and said second switchable current source is disabled when said first correction voltage is to be coupled to one of said connection points, and said second switchable current source is enabled and said first switchable current source is disabled when said second correction voltage is to be coupled to one of said connection points.