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Why pin3(non invert) of FET OPAMPs(AD549) has voltage?

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fala

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Hello, I measured voltage of non inverting pin3 of opamp with a standard voltmeter while pin3 was floating and opamp had been confgured as follower but it had about 13V output voltage(pin 6) enen when I grounded pin3 via a 100MOhm the result did not change. this opamp had input current of about 100 fA. can someone explain the phenomena and possibly the way it can be fixed, please?

PS-opamp is not damaged, I repeated the experiment with a few new ones but result was the same.
 

al37

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Hello,

I can says if I help you, can you add a copy (jpeg, img of the circuit) on this web site for have an idea.

Al
 

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