MEMS麦克风的低噪前置放大器及偏置电路设计

发布时间：2018-07-03 11:54

本文选题：MEMS麦克风 + 偏置电路　；参考：《西安电子科技大学》2015年硕士论文

【摘要】：随着无线通讯技术的迅猛发展,消费类电子产品日趋小型化、轻薄化和高度集成化。这些产品的声学输入部分的电路设计也面临着类似的要求。与传统的驻极体电容式麦克风ECM相比,MEMS麦克风具有体积小、成本低、一致性好、耐高温、抗震、工艺重复性好、便于大批量生产、易于集成等优点,使其成为目前消费类电子产品设计中的热门,为其设计专用集成电路也变得相当重要。本课题来源于启攀微电子(上海)有限公司,项目名称为CPM211,主要内容是采用umc35cdmos工艺为欧姆龙公司的一款MEMS麦克风芯片设计一款专用集成电路芯片,芯片中包含低噪前置放大器电路和偏置电路。前置放大器具有阻抗转换功能,可以提高MEMS麦克风输出信号的驱动能力,使后级功率放大器能正常工作,低噪技术则可在此基础上进一步降低SNR的损失。偏置电路主要由带隙基准源、振荡器和电荷泵构成,它输出一个15 V左右的偏置电压以驱动MEMS麦克风正常工作。本文首先介绍本课题研究的目的和意义,然后以麦克风的发展史为铺垫,重点介绍了电容式MEMS麦克风的相关电学参数,为后面制定设计目标提供参考。作为电路设计的框架和依据,MEMS麦克风的低噪前置放大器及偏置电路的系统架构以及理论基础占据了本文四分之一的篇幅。本文的重点部分,详细介绍了低噪前置放大器和偏置电路的电路图,以及使用仿真工具对各个模块进行仿真的过程和结果。考虑到电路设计流程的完整性,本文针对版图设计的流程以及设计中需要重点考虑的因素做了一般性的介绍。在代工厂将MEMS麦克风的低噪前置放大器及偏置电路裸片与MEMS麦克风裸片封装成一个芯片后,本文详细描述了对芯片样品的测试过程和结果。测试结果显示MEMS麦克风的低噪前置放大器及偏置电路芯片与MEMS麦克风芯片封装成品的总电流为160μA、灵敏度为-42 dB,频响曲线在带内平滑,SNR约为60 dB,THD小于0.2%,偏置电压BIAS为15.2V,低噪前置运放的增益为4.5 dB,各项测试指标都能够满足要求。本文提供的MEMS麦克风前置放大器电路和偏置电路方案具有噪声小、灵敏度高、DC-DC升压转换效率高、功耗低等特点,在消费类电子产品中具有极强的工程实用性。
[Abstract]:With the rapid development of wireless communication technology, consumer electronic products are becoming miniaturized, thin and highly integrated. The circuit design of the acoustic input part of these products faces similar requirements. Compared with the traditional electret capacitive microphone ECM, MEMS microphones have the advantages of small size, low cost, good consistency, high temperature resistance, seismic resistance, good process repeatability, easy mass production and easy integration. It has become a hot topic in the design of consumer electronic products, and it is very important to design ASIC for it. The project is named CPM211.The main content of this project is to design a special integrated circuit chip for a MEMS microphone chip of OMRON by using umc35cdmos technology. The chip includes a low-noise preamplifier circuit and a bias circuit. The preamplifier has the function of impedance conversion, which can improve the driving ability of the output signal of MEMS microphone and make the power amplifier work normally. The low noise technology can further reduce the loss of SNR on this basis. The bias circuit consists of a bandgap reference source, an oscillator and a charge pump. It outputs a bias voltage of about 15 V to drive the MEMS microphone to work properly. In this paper, the purpose and significance of this research are introduced first, and then the related electrical parameters of capacitive MEMS microphones are introduced with emphasis on the history of microphone development. As the frame of circuit design and the system architecture and theoretical basis of low-noise preamplifier and bias circuit based on MEMS microphones, this paper occupies the space of 1/4. In the key part of this paper, the circuit diagram of low noise preamplifier and bias circuit is introduced in detail, and the simulation process and result of each module are also given. Considering the integrity of the circuit design process, this paper introduces the layout design process and the key factors in the design. After the low noise preamplifier of MEMS microphone and the bare chip of bias circuit and the bare chip of MEMS microphone are encapsulated into a chip in the manufacturing plant, the testing process and results of the chip sample are described in detail in this paper. The test results show that the total current of MEMS microphone preamplifier, bias circuit chip and MEMS microphone chip package is 160 渭 A, the sensitivity is -42 dB, the frequency response curve is 60 dB THD less than 0.2 in the band smooth, the bias voltage is bias. The gain of low noise preamplifier is 4.5 dB, and all the test indexes can meet the requirements. The MEMS microphone preamplifier circuit and bias circuit provided in this paper have the advantages of low noise, high sensitivity, high efficiency of DC-DC boost conversion and low power consumption.
【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】：TN722.71

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