【作者】 李铭；

【导师】 陈莹梅； 赵来定；

【作者基本信息】 东南大学 ， 集成电路工程（专业学位）， 2021， 硕士

【摘要】 随着5G网络的快速发展,大型数据中心对光接口数据速率的需求大大增加。四阶脉冲幅度调制(PAM4)通过提高每个码元周期携带的位数,来有效增加信息传输容量,满足高速系统的需求。本文研究的是光互连系统中的前置放大电路,属于光接收机的模拟前端,前置放大器用来将光电二极管的单端电流信号转换为符合后级数字电路判决逻辑的差分电压信号。电路基于0.13μm SiGe BiCMOS工艺,对前置放大器进行研究,电路设计主要考虑噪声、跨阻增益、带宽、线性度和功耗等指标。所设计的前置放大器包括高速主通路电路和低速模块,其中,高速主通路是4级级联电路,从输入到输出分别是跨阻放大器、可变增益放大器、均衡电路和输出缓冲器,低速模块主要有直流偏移消除电路以及由I-V转换和比较器构成的增益控制电路。低噪声、高带宽和高线性度之间的权衡是本文设计的挑战,跨阻放大器采用电压并联负反馈结构实现低噪声,并在电路中增加增益切换,来保证在输入电流动态变化范围下系统的高线性度,同时通过后级可变增益放大器和均衡电路,来补偿跨阻放大器在大增益下为实现低噪声而造成的带宽的损失,实现系统的高带宽。本文设计的28Gbaud/s PAM4光接收机前置放大器级联自动增益控制(AGC)环路构成前端放大电路,整体版图尺寸为899μm× 1215μm。后仿真结果显示:-3dB带宽大于21.6GHz,跨阻增益动态范围为42.1dBΩ～71.8dBΩ,输入电流在80μA～2mA的动态变化范围下,前置放大器差分输出电压摆幅稳定在590mV～610mV之间,等效输入噪声电流为2.32μA,电路总谐波失真(THD)为4.62%,在3.3V电源电压下共消耗219.12mW的直流功耗。以上指标的后仿真结果均满足原定指标要求,且裕量充足,电路性能良好。更多还原

【Abstract】 With the rapid development of 5G network,the demand for optical interface data rate in large data centers is greatly increased.Fourth-order pulse amplitude modulation(PAM4)can increase the capacity of information transmission by increasing the number of bits carried per code cycle to meet the requirements of high-speed systems.The pre-amplifier circuit is studied in the optical interconnection system,which belongs to the analog front end of optical receiver.The pre-amplifier is used to convert the single-ended current signal of the photodiode into the differential voltage signal in accordance with the decision logic of the digital circuit at the later stage.The circuit is based on 0.13 μm SiGe BiCMOS technology,and the pre-amplifier is studied.The circuit design mainly considers the noise,transresistance gain,bandwidth,linearity and power consumption.The pre-amplifier designed include main channel circuit with high speed and low speed module.Among them,the main channel is four display circuits,which are the transresistance amplifier,the variable gain amplifier,the balance circuit and the output buffer from input to output.The low speed module has the DC offset elimination circuit and the gain control circuit composed of I-V converter and a comparator.The trade off between low noise,high bandwidth and high linearity is the design challenge of the dissertation.The transresistance amplifier use voltage parallel negative feedback to achieve low noise and add gain switching in the circuit,which ensure high linearity of the system under the dynamic range of input current.And the high bandwidth of the system is realized through the variable gain amplifier and equalization circuit,which compensate for the bandwidth loss caused by low noise in the high gain.In this dissertation,the pre-amplifier of 28Gbaud/s PAM4 optical receiver is designed by cascading automatic gain control(AGC)loop,which forms the front-end amplifier circuit.The overall layout size is 899μm× 1215μm.The post-simulation results show that the bandwidth is greater than 21.6GHz,the dynamic range of the transimpedance gain is 42.1 dBΩ～71.8dBΩ,the swing of the differential output voltage of the pre-amplifier is stable between 590mV～610mV under the input dynamic current range of 80μA～2mA,the equivalent input noise current is 2.32μA,the total harmonic distortion(THD)of the circuit is 4.62%and the DC power consumption of 219.12mW is consumed at 3.3V supply voltage.The post-simulation results of the above indexes meet the requirement of the original indexes.The margin is sufficient and the circuit performance is good.更多还原