Low-power buffer with voltage boosting and improved frequency compensation for liquid crystal display source drivers

A pair of complementary class-A buffers with voltage boosting method and improved frequency compensation is proposed. The buffer driving capabilities are enhanced by adding small auxiliary transistors to pull-up/pull-down the gate voltages of the buffer output transistors to improve the transient response. The auxiliary transistors are turned off for power saving in the steady-state operation. The proposed frequency compensation is more area-efficient than the Miller compensation method and hence maintains the high output voltage slew rate of the buffer. The measured static current of each buffer with the proposed circuits consumes 3 μA under a supply voltage of 5 V. The buffer settling times of the rising and the falling edges with a capacitance of 600 pF for an input swing of 5 V are 3.3 and 1.7 μs, respectively. The core size of the buffers including the compensation capacitance is 82 × 101 µm2 and the buffer can be stable when a load capacitance changes from 5 to 600 PF. Hence, the proposed output buffers concurrently achieve a fast response and are suitable for a wide range of load capacitances.