Patent ID: 8736373

Claim:
An output buffer, applied in a source driver of a liquid crystal display, the output buffer comprising: a buffer input, for receiving an input voltage; a buffer output, for outputting an output voltage; a differential input stage, coupled to the buffer input and the buffer output; a bias current source, coupled to the differential input stage; an output stage, coupled between the differential input stage and the buffer output, the output stage being operated between an analog supply voltage (AVDD) and a ground voltage (AGND); a compensation capacitor, having one end coupled between the differential input stage and the output stage and the other end coupled between the output stage and the buffer output; and a comparator, operated between the analog supply voltage (AVDD) and the ground voltage (AGND), two comparator inputs of the comparator being coupled to the buffer input and the buffer output respectively, a comparator output of the comparator being coupled to the bias current source, the comparator comparing the input voltage with the output voltage and outputting a control signal to the bias current source according to the compared result to control a bias current outputted by the bias current source; wherein the bias current source comprises a P-type bias current source and a N-type bias current source, the P-type bias current source is coupled between the analog supply voltage (AVDD) and the differential input stage, the N-type bias current source is coupled between the differential input stage and the ground voltage (AGND), the comparator output of the comparator is coupled to the P-type bias current source and the N-type bias current source.