大线性度低功耗OTA及其滤波器研究与设计

发布时间：2018-04-06 07:27

本文选题：低功耗　切入点：低压　出处：《西安电子科技大学》2015年硕士论文

【摘要】：随着移动通信产品、可穿戴设备,便携式生物医疗器件等需要电池供电的移动电子产品的性能不断提高,使用市场的不断扩大,使得对于如何减小电路功率消耗成为重要的研究方向。因此,对于低功耗模拟IC设计技术的研究变得极其必要且意义重大。模拟滤波器作为模拟信号处理中广泛应用的模块,关于它的的低功耗研究对于整个模拟IC的低功耗设计是很有帮助的,本文重点研究凭借优越的性能一直被广泛使用的OTA-C滤波器。本文参考了国内外大量关于低压低功耗模拟IC设计的方法,通过对这些方法性能表现的全面分析与评估,采用亚阈值区电路作为本文低功耗研究的重点方向。接着研究了跨导放大器的原理并且分析了其在饱和区和亚阈值区的直流特性,可以知道亚阈值区的OTA(跨导运算放大器)输出电流与输入的差分电压是双曲正切函数的关系,以此作为基础,解决亚阈值区输入线性范围过小的问题。本文用了四种方法来改善OTA输入线性范围:源级负反馈、栅极负反馈、衬底驱动以及一种特殊电路结构——Bump线性化结构,其中衬底驱动既有效降低了对电源电压的要求并且可以使栅极空出来提供反馈,Bump电路是在差分对管的两条支路中间增加一条包含两个管子的支路,可以有效提高像亚阈值区OTA这种具有双曲正切函数关系的电路结构的输入线性范围。这四种方法在提高线性度的同时也使得跨导增益降低了,造成OTA直流增益过小,不利于推广使用,因此,本文又使用了一种改进的新型电流镜作为输出级,大大提高了输出阻抗,进而使得直流增益增大,并且这种新型的电流镜同时也是适合低电源电压应用的。最后将这种OTA应用到最终设计的OTA-C滤波器中,实现低压低功耗大输入摆幅的设计。本文所有的电路使用的都是0.18μm标准CMOS工艺,在Cadence的Virtuoso Schematic Compose上完成电路设计,然后再在Analog Design Environment上进行仿真验证,通过仿真显示,在0.9V的电源电压下,最终完成的OTA直流增益可以达到40dB以上,截止频率约为55kHz,输入线性范围由原来的几十毫伏提升到?1V,并且功耗只有110nW,由其所构成的OTA-C滤波器截止频率约600Hz,输入摆幅可以达到0.8V,通带较平坦,阻带衰减较快,总体来说性能良好,最终也只有不到400nW的功耗。可以看出,本文所设计的OTA及其所构成的滤波器是符合我们所要求的大线性度低功耗要求的。作为通用模块,本文所设计的OTA以及OTA-C滤波器是可以在模拟IC低功耗设计中起到关键作用的。
[Abstract]:As mobile communications products, wearable devices, portable biomedical devices, and other mobile electronics that require battery power continue to improve their performance and the market for use continues to expand,Therefore, how to reduce the power consumption of the circuit becomes an important research direction.Therefore, the study of low-power analog IC design technology becomes extremely necessary and significant.As a widely used module in analog signal processing, the research on the low power consumption of analog filter is helpful to the low power design of the whole analog IC.This paper focuses on OTA-C filters, which have been widely used by virtue of their superior performance.This paper refers to a large number of methods of low voltage and low power analog IC design at home and abroad. Through the comprehensive analysis and evaluation of the performance of these methods, the sub-threshold circuit is adopted as the focus of the research on low power consumption in this paper.Then, the principle of transconductance amplifier is studied and its DC characteristics in saturation region and sub-threshold region are analyzed. It can be known that the output current of OTA in the sub-threshold region is a hyperbolic tangent function with the input differential voltage, and the OTA (transconductance operational amplifier) output current in the sub-threshold region is a hyperbolic tangent function.Based on this, the problem that the input linear range of subthreshold region is too small is solved.In this paper, four methods are used to improve the linear range of OTA input: source-level negative feedback, gate negative feedback, substrate drive, and a special circuit structure Bump linearization structure.The substrate driver can effectively reduce the requirement of the power supply voltage and can make the gate empty to provide feedback. The Bump circuit adds a branch containing two tubes between the two branches of the differential pair.It can effectively improve the input linear range of circuit structures with hyperbolic tangent function such as sub-threshold region OTA.These four methods not only improve the linearity but also reduce the transconductance gain, which results in the OTA DC gain being too small, which is not conducive to popularization. Therefore, an improved new type of current mirror is used as the output stage in this paper.The output impedance is greatly increased, and the DC gain is increased, and this new type of current mirror is also suitable for the application of low power supply voltage.Finally, this OTA is applied to the final design of OTA-C filter to realize the design of low voltage and low power consumption and large input swing.All the circuits used in this paper are 0.18 渭 m standard CMOS process. The circuit is designed on the Virtuoso Schematic Compose of Cadence, and then simulated on the Analog Design Environment.The final OTA DC gain can reach 40dB,The cutoff frequency is about 55kHz, the input linear range is raised from tens of millivolts to 1V, and the power consumption is only 110nW. The cut-off frequency of the OTA-C filter is about 600Hz, the input swing can reach 0.8V, the passband is flat, and the stopband attenuation is faster.Overall performance is good, and ultimately less than the power consumption of 400nW.It can be seen that the OTA and the filter designed in this paper meet the requirements of large linearity and low power consumption.As a universal module, the OTA and OTA-C filters designed in this paper can play a key role in the low power design of analog IC.
【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】：TN713

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