流水线模数转换器中的宽带电流型运算放大器

Wide band current-mode amplifier for pipelined ADC

针对高清视频信号处理对动态范围大,运算速度快的模数转换器(ADC)的要求,提出了一种流水线宽带电流型运算放大器。该运算放大器的主放大器采用套筒式增益提高结构,辅助运算放大器用电流型放大器替代。采用电流共模反馈电路调节主运算放大器的支路电流以稳定输出共模电平;采用TSMC 0.18μm CMOS工艺设计电路。实验结果显示:辅助运算放大器采用源极输入,减小了信号主通路上的寄生电容,提高了整个运算放大器的电路速度。运算放大器的增益为83.19dB,相位裕度为61.6°,单位增益带宽为1.6GHz,功耗为9.3mW;在满幅度阶跃输入的情况下,输出建立时间小于1.83ns。将该运算放大器用于高清视频信号的流水线ADC中,实现了170MS/s,10bit精度的模数转换。同传统的电压型运算放大器相比,该运算放大器响应速度更快,功耗更低,可满足处理视频信号的要求。

A novel bandwidth current operational amplifier was presented to meet the demand of video signal processing for a pipelined Analog-to-Digital Converter（ADC） with large dynamic ranges andhigher operation speeds. In the system, the main amplifier adopts a cascode structure and the auxiliary amplifier is a current mode amplifier. In order to improve circuit speeds and to decrease parasitic ca-pacitance, the input signal was applied to the source terminal. A current-mode feedback circuit was u-pacitance, the input signal was applied to the source terminal. A current-mode feedback circuit was u- tilized to stabilize the out common mode voltage through adjusting the currents of the main amplifierand the amplifier was implemented in TSMC 0.18μm CMOS process with a consumer of 9.3 mW. Experiment results show that the circuit has an open loop gain of 83.19dB, a unity gain bandwidth of1.6 GHz and a phase margin of 61.6°. A pipelined ADC for high-resolution video signal process using this current amplifier achieves a resolution of 10 bit and a sampling rate of 170 MS/s. Compared withtraditional amplifiers , the proposed amplifier shows a lower power dissipation and higher response speeds and satisfies the requirements of the video signal processing.