The OP
Published on 2019-5-6 13:48
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In fact, when the voltage input op amp is in the linear working area, there is "virtual disconnection" and "virtual short circuit" at the two input terminals. The existence of "virtual disconnection" means that the input current of the two input terminals is very small, so that it can be regarded as an open circuit.
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Published on 2019-5-7 10:14
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Published on 2019-5-6 13:52
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This post is from Analog electronics
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Originally I thought that if the non-inverting input terminal P2 of A2 is virtual ground, then Up2=0, and Un2=0, then Un1=Up1=0; In the figure below on the 6th floor, the non-inverting input terminal of A2 is originally grounded through a resistor, so where does the "P2 virtual ground" come from?
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Published on 2019-5-6 15:11
Originally I thought that if the non-inverting input terminal P2 of A2 is virtual ground, then Up2=0, and Un2=0, then Un1=Up1=0; In the figure below on the 6th floor, the non-inverting input terminal of A2 is originally grounded through a resistor, so where does the "P2 virtual ground" come from?
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Published on 2019-5-6 15:07
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Published on 2019-5-6 14:20
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Published on 2019-5-6 15:07
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Published on 2019-5-6 15:11
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This post is from Analog electronics
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"What are the potentials of Up2 and Un2 respectively?" Please note what I said on the 8th floor: "When the input Ui is positive, op amp A2 is not in the linear operating area, so there is no "virtual break" or "virtual short" between the two input terminals of A2." Up2 and Un2 are different for positive and negative inputs.
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Published on 2019-5-6 20:54
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Published on 2019-5-6 20:54
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Published on 2019-5-7 07:47
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This post is from Analog electronics
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"How can the current at the two op amp inputs be zero?" For an ideal op amp, the input impedance is infinite, so of course the input current is zero. For a non-ideal op amp, the input impedance is also quite large, and the input current is usually less than 1uA, or even up to pA. Only current-input op amps have slightly larger input currents.
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Published on 2019-5-7 09:21
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Published on 2019-5-7 09:21
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Published on 2019-5-7 09:31
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This post is from Analog electronics
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In fact, when the voltage input op amp is in the linear working area, there is a "virtual disconnection" and "virtual short" at the two input terminals. The existence of a "virtual disconnection" means that the input current of the two input terminals is so small that it can be regarded as an open circuit.
Details
Published on 2019-5-7 10:14
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Published on 2019-5-7 10:14
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