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AD8302的输出不正确

我使用AD8302设计了一个幅相检测电路,如下图所示,

我测试的时候是用波形发生器产生1KHz,200mVp-p的正弦信号加在两个输入信号端,然后用示波器观测。结果我测得VREF引脚输出1.85V,INPA和INPB的引脚上都是4.96V,输出VMAG和VPHS都是5.06V,这是怎么回事啊?我不明白一个正弦信号经过电容耦合后为什么会多了将近5V的直流分量?是我的芯片坏了吗?求救!!!急!!!!万分感谢!!!!!

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  • 您好!

    输入引脚具有直流偏置电压,因此在输入引脚会测到直流电压,数据手册中描述如下,供您参考。

    The single-ended input interfaces for both channels are identical. Each consists of a driving pin, INPA and INPB, and an ac-grounding pin, OFSA and OFSB. All four pins are internally dc-biased at about 100 mV from the positive supply and should be externally ac-coupled to the input signals and to ground. For the signal pins, the coupling capacitor should offer negligible impedance at the signal frequency. For the grounding pins, the coupling capacitor has two functions: It provides ac grounding and sets the high-pass corner frequency for the internal offset compensation loop. There is an internal 10 pF capacitor to ground

    that sets the maximum corner to approximately 200 MHz.

    对于AD8302工作于低频频率,请参考应用笔记AN-691AD8302相关内容请参考1315页。

    AN-691.pdf
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  • 您好!

    输入引脚具有直流偏置电压,因此在输入引脚会测到直流电压,数据手册中描述如下,供您参考。

    The single-ended input interfaces for both channels are identical. Each consists of a driving pin, INPA and INPB, and an ac-grounding pin, OFSA and OFSB. All four pins are internally dc-biased at about 100 mV from the positive supply and should be externally ac-coupled to the input signals and to ground. For the signal pins, the coupling capacitor should offer negligible impedance at the signal frequency. For the grounding pins, the coupling capacitor has two functions: It provides ac grounding and sets the high-pass corner frequency for the internal offset compensation loop. There is an internal 10 pF capacitor to ground

    that sets the maximum corner to approximately 200 MHz.

    对于AD8302工作于低频频率,请参考应用笔记AN-691AD8302相关内容请参考1315页。

    AN-691.pdf
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