A Low Offset High Voltage Swing Rail-to-Rail Buffer Amplifier for LCD Driver

The size of LCDs is getting larger in particular , it is essential to compromise the driving ability. So , source drivers with high performance, high resolution, and low power dissipation will achieve more additional value. This paper presents a design and implementation of using 10-bit multiple DAC (digital to analog converter) for the driver , and proposes a rail-to-rail output buffer with low offset and high driving ability. We designed a class-B output buffer with offset compensation ability to reduce the nonlinearity of output voltage. With the H-SPICE model of TSMC 0.35 mum 2P4M 3.3 V / 5 V process, the maximum offset is less than 2 mV , and the input / output swing are nearly full swing. Besides , it also performs a rail-to-rail swing range and high slew rate of 14 V / mus and 11.5 V /mus for rising and falling edges under a 400 pF capacitance load. For high driving capability , two push-pull output stages are used , two frequency compensation stages are also introduced for stability , one is the miller compensation with 0.04 pF capacitance , and the other is zero compensation with 0.1 kOmega added between two push-pull output stages for stable driving under different capacitance loads. The result exhibits that the settling time are within 5 mus under the max voltage swing with voltage 5 V under a 400 pF capacitance load. Even under a 1000 pF capacitance load , it still has the settling time of 1.52 mus and 1.80 mus for rising and falling edges , respectively. The effective area of this buffer is only 100 x 100 mum² with build-in offset voltage holding capacitor.