一种具有高转换速率的轨对轨运算放大器

为了驱动液晶显示器背板形成不同的灰阶，设计了一种利用齐纳二极管的稳压原理，实现恒定跨导用于TFT-LCD液晶显示的片内运算放大器。采用互补差分输入级，实现了Rail-to-Rail的共模电压输入范围；一种新颖的转换速率增强结构，加快了运算放大器的响应速度；输出级采用Class AB类控制电路，并将其嵌入到求和电路中，以保证较低的噪声和失调。直流增益为101dB，单位增益带宽为13MHz，相位裕度为64°。仿真结果证明该运算放大器工作良好，其面积为500μm×380μm。

Design of Rail-to-Rail Op-Amp with High-Slew Rate

To drive the backplane of a liquid crystal display device and attain different kinds of grey level, a compact CMOS Rail-to-Rail input stage with constant-gm is presented. A zener diode is inserted between the tails of the complementary input pairs to keep the gm of the input stage constant. A novel slew rate enhanced circuit is implemented to achieve a very high slew rate; The Class AB control is shifted into the summing circuit, which results in a low noise and offset of the amplifier. The low frequency gain is up to 101dB, and the results indicate that the circuit works well and effectively. The chip area of the operational amplifier circuit is 0.19mm2.