【摘要】：隨著科學(xué)技術(shù)的高速發(fā)展,越來(lái)越多的領(lǐng)域涉及到微弱信號(hào)的檢測(cè)與分析。微弱信號(hào)通過(guò)各類傳感器轉(zhuǎn)換為電學(xué)信號(hào),傳感器輸出的電信號(hào)通常頻率較低且十分微弱,需要經(jīng)過(guò)前置放大器放大輸出。在微弱信號(hào)檢測(cè)系統(tǒng)中,前置放大器是整個(gè)檢測(cè)系統(tǒng)的關(guān)鍵模塊,這使得低噪聲高增益放大器的研究成為一個(gè)重要課題。本文的主要目的是設(shè)計(jì)一款適用于傳感器輸出信號(hào)放大的高增益、低噪聲、輸出無(wú)失真的前置放大電路。本文從放大傳感器輸出的微弱信號(hào)出發(fā),提出了放大電路的設(shè)計(jì)指標(biāo)。通過(guò)對(duì)常用的集成放大電路優(yōu)缺點(diǎn)分析,提出了使用結(jié)型場(chǎng)效應(yīng)管作為輸入器件設(shè)計(jì)噪聲性能更高的放大電路方案。在具體的電路設(shè)計(jì)中使用優(yōu)先考慮噪聲特性的設(shè)計(jì)方法:先確定滿足噪聲要求的輸入級(jí)器件,選定合適的工作點(diǎn),設(shè)計(jì)偏置電路,確定有源器件的電路組態(tài),最后設(shè)計(jì)反饋網(wǎng)絡(luò)和補(bǔ)償電路。這種設(shè)計(jì)方法可以使電路做到噪聲最佳。本次設(shè)計(jì)的放大電路由兩級(jí)放大級(jí)聯(lián)構(gòu)成,由于應(yīng)用于低頻環(huán)境下,所以兩級(jí)之間采用直接耦合方式。整個(gè)放大電路主要由輸入級(jí)、輸出級(jí)、偏置電路、反饋電路和補(bǔ)償電路構(gòu)成。完成電路整體設(shè)計(jì)后,使用PSpice軟件對(duì)放大電路整體進(jìn)行電壓增益、瞬態(tài)分析、等效輸入噪聲、共模抑制比等方面的仿真,得出的仿真結(jié)果顯示所設(shè)計(jì)的放大器差模電壓增益為1071倍,上限截止頻率達(dá)到了585k Hz,共模抑制比在所要求的工作頻率內(nèi)高于90d B,等效輸入噪聲為納伏級(jí)別,滿足了設(shè)計(jì)要求。為了進(jìn)一步驗(yàn)證放大電路的可行性,制作實(shí)際電路板,對(duì)其進(jìn)行了小信號(hào)輸入-輸出測(cè)試和頻率特性測(cè)試,實(shí)際的測(cè)試結(jié)果表明放大器能夠無(wú)失真地放大低頻微弱信號(hào)。
[Abstract]:With the rapid development of science and technology, more and more fields involve weak signal detection and analysis. The weak signal is converted into electrical signal by various sensors. The signal output by the sensor is usually low frequency and very weak, so it needs to be amplified by preamplifier. In the weak signal detection system, the preamplifier is the key module of the whole detection system, which makes the research of low noise and high gain amplifier become an important subject. The main purpose of this paper is to design a preamplifier circuit with high gain, low noise and no distortion. Based on the weak signal output from the amplifier sensor, the design index of the amplifier circuit is presented in this paper. Based on the analysis of the advantages and disadvantages of common integrated amplifier circuits, a scheme of using junction FET as input devices to design amplifiers with higher noise performance is proposed. In the specific circuit design, the design method of priority noise characteristic is used: first, the input level device that meets the noise requirement is determined, the suitable working point is selected, the bias circuit is designed, and the circuit configuration of the active device is determined. Finally, the feedback network and compensation circuit are designed. This design method can make the circuit noise optimal. The amplifier circuit is composed of two stage amplifier cascade. Because it is used in low frequency environment, direct coupling is adopted between the two stages. The amplifier circuit consists of input stage, output stage, bias circuit, feedback circuit and compensation circuit. After the overall design of the circuit is completed, the voltage gain, transient analysis, equivalent input noise and common-mode rejection ratio of the amplifier circuit are simulated by using PSpice software. The simulation results show that the differential mode voltage gain of the designed amplifier is 1071 times, the upper cutoff frequency reaches 585k Hz, common mode rejection ratio is higher than 90 dB in the required operating frequency, and the equivalent input noise is nanovolt level. Meet the design requirements. In order to further verify the feasibility of the amplifier circuit, the practical circuit board is fabricated, and the small signal input-output test and the frequency characteristic test are carried out. The actual test results show that the amplifier can amplify the low frequency weak signal without distortion.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN722.71

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