宽幅CMOS可编程增益放大器研究

发布时间：2018-01-16 13:31

本文关键词：宽幅CMOS可编程增益放大器研究　出处：《西安电子科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：对于CCD图像处理系统,可变增益放大器(VGA)是CCD处理器中模拟前端(AFE)电路的一个重要组成模块。基于CMOS工艺的VGA可以用来在不同环境下设置不同增益值,调节输入信号动态范围并且稳定输出信号功率,提供一个恒定输出摆幅信号给后级模数转换(ADC)电路。VGA处于CCD系统的模拟前端电路,需要处理的CCD信号摆幅较大,宽幅高线性是本论文的一个重要的设计指标。另外基于AGC系统,要求VGA的增益控制特性是呈dB线性,所以宽范围dB线性是本论文设计的另一重要指标。基于CCD系统为应用背景,本文首先提出了一款宽幅CMOS可编程增益放大器,可以处理输入摆幅为0~2V的离散信号或连续信号,并将其放大到满摆幅为2V输出信号供给后级ADC进行处理,有效位数达到15.81位。该PGA主要由四大部分组成:电压钳位电路、源极跟随电路、R-2R电阻衰减网络以及固定增益值放大器。其中设计难点主要在于固定增益放大器中高性能三级运放的稳定性设计,并且引入了电流镜补偿和共源共栅补偿两种补偿方法使得运放工作稳定。本设计PGA基于SMIC0.18μm 1P6M CMOS工艺,电源电压3V下,实现了42dB增益变化范围(-1.08~41.06dB),增益步长为6dB,-3dB带宽不随增益变化,达到114.58MHz。对于AGC系统中VGA的增益控制呈dB线性,提出了一款宽范围CMOS开环VGA。VGA主要有三大部分:指数函数控制电路、可变增益电路以及共模反馈(CMFB)电路。其中指数函数控制电路是利用新型指数近似方程式拟合构造CMOS控制电路,明显提升了dB线性范围,增益可变电路则基于负载和跨导同时改变结构实现。同样基于SMIC 0.18μm 1P6M CMOS工艺,电源电压3V下,VGA仿真结果为增益值-30dB~32dB连续变化,dB线性增益范围达到62dB,且误差在±3dB之内,VGA输入1dB压缩点IP1dB为-20.79~8.72dBm以及电路-3dB带宽变化从269.6MHz(最大增益32dB处)到2.609GHz(最小增益-30dB处)。
[Abstract]:For the CCD image processing system, a variable gain amplifier (VGA) is a CCD analog front-end processor (AFE) is an important component of the module circuit. CMOS technology based on VGA can be used to set different gain values under different environmental conditions, adjusting the dynamic range of input signal and stable output signal power, providing a constant output voltage swing after the level signal to the analog-to-digital conversion (ADC) circuit.VGA in analog front-end circuit of CCD system, CCD signal processing swing is large, wide and high linearity is an important design index in this paper. In addition, based on the AGC system, VGA is a dB linear gain control characteristics, so a wide range of dB is linear another important index in this thesis. Based on the CCD system as the application background, this paper proposes a wide CMOS programmable gain amplifier, can handle input swing for 0~2V discrete or continuous signal, And amplify it to full swing for the output signal of the 2V supply after ADC treatment, effective number reached 15.81. The PGA is mainly composed of four parts: the voltage clamp circuit, source follower circuit, R-2R resistance attenuation network and fixed gain amplifier. The design difficulty lies in the stability design of three stage operational amplifier high performance fixed gain amplifier, and the introduction of the current mirror compensation and cascode compensation two compensation method makes the operational amplifier stability. The design of PGA SMIC0.18 m 1P6M CMOS process based on the voltage supply of 3V, the 42dB gain range (-1.08~41.06dB), the gain step is 6dB, -3dB bandwidth with the gain changes, to reach 114.58MHz. for AGC system in VGA is dB linear gain control, proposed a wide range of CMOS open loop VGA.VGA consist of three parts: the exponential control circuit, variable gain circuit and Common mode feedback circuit (CMFB). The exponential control circuit is to use the new exponential approximation equation to construct the CMOS control circuit, significantly enhance the dB linear range, a variable gain circuit load and transconductance based on structure changed at the same time. The same SMIC 0.18 m 1P6M CMOS process based on the voltage supply of 3V, the simulation results of VGA for gain the value of continuous changes of -30dB~32dB, dB linear gain range is up to 62dB, and the error was within 3dB, VGA input 1dB compression point of IP1dB for -20.79~8.72dBm and -3dB circuit bandwidth changes from 269.6MHz (maximum gain 32dB) to 2.609GHz (minimum gain -30dB).

【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN722

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