运算放大器是信号处理中的基础模块，是高性能混合信号数据转换器、片上系统(SoC)等的重要组成部分。低功耗和高性能的基础电路模块成为系统发展的瓶颈，因此对增益和带宽增强型运算放大器的研究成为业界关注的焦点。为了研究运算放大器增益和带宽优化设计技术，实现低功耗高性能的解决方案，对电流重用技术的产生背景和技术演进作了较为详细的分析，体现了在技术进步过程中对结构的优化和改进，对高性能系统集成设计具有重要的参考意义。

Operational amplifier is one of the basic blocks of signal processing applications, and the essential component for high performance mixed signal data converter and System-on-Chip(SoC) as well. As the complexity of the systems increases, low power and high performance are required, which becomes the bottle neck for further application. Therefore, the gain and bandwidth enhancement techniques become the highlights for the circuit designers. To understand the design techniques of optimizing the gain and bandwidth, this paper will focus on the current recycling techniques for performance optimization. The progresses of the techniques are listed and discussed in detail. The comparison among the structures will be given on the advantages and disadvantages. This work can provide an essential reference for the system integration.