低功耗解決方案地址傳感器的激勵要求

　　有源傳感器，需要激發(fā)產(chǎn)生可測量的輸出，工程師可以把多種選擇提供所需的電流或電壓水平。從簡單的基于運放的勵磁電路到高度集成的多功能集成電路，可供選擇的設(shè)備包括一系列設(shè)備，包括線性技術(shù)、微芯片技術(shù)和德克薩斯儀器等。

　　隨著人們對物聯(lián)網(wǎng)的興趣越來越大，傳感器子系統(tǒng)構(gòu)成了許多預(yù)計將在薄膜電池和能量收集技術(shù)上運行多年的設(shè)計的核心?？煽康臏y量，但是，基于許多傳感器的電阻，如熱敏電阻、電阻溫度檢測器（RTD），應(yīng)變計，和其他需要激發(fā)一個電流源或電壓源產(chǎn)生的電輸出。

　　An excitation current source output voltage of an RTD is directly proportional to the device‘s resistance. Although the use of high-excitation current would suggest larger voltage output， RTD resistance increases as its temperature rises from the higher current. Conversely， thermistor resistance drops as its temperature rises from similar self-heating effects. Beyond those types， other transducers such as Hall-Effect sensors， exhibit performance characteristics that vary significantly with applied excitation. As a result， active sensors typically require excitation maintained within strict limits to ensure reliable measurement with minimal nonlinearity.

　　Engineers can build simple excitation circuits using an available current-source IC， such as the Texas Instruments REF200， and a basic op amp， such as the TI OPA188 （Figure 1）。 With this approach， engineers can use two matched excitation sources produced by the current-source IC to adjust the op amp’s output voltage to zero at the low end of the desired sensor-measurement range.