Operational Amplifier

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Operational Amplifier [Copy link]

 

What is the relationship between the output voltage value of 1 and 1 and 2 in the circuit diagram? 2 should be a current sampling. Why does my Multisim simulation output value remain unchanged regardless of how 1 and 2 are changed?

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Just looking at your simulation diagram, the current source gets the voltage through the resistor, and a simple in-phase input proportional amplification is fine. But the peak-to-peak value of your test value in the upper right corner is not what I understand. It is pure DC, so it is normal for the peak-to-peak value to be 0. Why is the effective value also 0? This explanation does not make sense. Is there something wrong with your source or software settings?

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Alas, published on 2024-2-5 11:30 Just looking at your simulation diagram, the current source gets the voltage through the resistor, a simple in-phase input proportional amplification, there is no problem. But your test in the upper right corner...

is a DC current source given by

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Zhufeng. Posted on 2024-2-5 11:33 It is a DC current source

Even if I directly apply a voltage there and change 1, the output of the op amp does not change

maychang

Zhufeng. Posted on 2024-2-5 11:34 Even if I directly give a voltage there and change 1, the output of the op amp will not change

Your LM358 uses positive and negative 5V power supply simulation. Under the 5V power supply voltage, the LM358 output reaches 3.5V and cannot rise any higher.

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Zhufeng. Posted on 2024-2-5 11:34 Even if I directly give a voltage there and change 1, the output of the op amp will not change

Indeed, what the moderator said is right. You amplified 0.78V by 83 times, which indeed exceeds the output range. I didn't pay attention to your gain and only looked at the bottom.

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Alas, published on 2024-2-5 13:39 The moderator is right. You amplified 0.78V by 83 times, which is indeed beyond the output range. I didn't pay attention to your gain, but only looked at the bottom.

No matter how I give the value, it doesn't work, so how can I see the input and output relationship?

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Zhufeng. Posted on 2024-2-5 11:34 Even if I directly give a voltage there and change 1, the output of the op amp will not change

Why? Is it because of the circuit or because my simulation is wrong?

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Zhufeng. Posted on 2024-2-5 15:18 No matter how I give the value, it doesn't work, so how can I see the input and output relationship?

Please advise, how can I make a normal simulation?

呜呼哀哉

Zhufeng. Posted on 2024-2-5 15:20 Please advise, how can I make a normal simulation

To make it simpler, change your R68 to 300Ω, set the gain to 2, and then change the current source value to see the output change.

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Zhufeng. Posted on 2024-2-5 11:34 Even if I directly give a voltage there and change 1, the output of the op amp will not change

Can you help me write the input-output relationship?

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Alas, published on 2024-2-5 13:39 The moderator is right. You amplified 0.78V by 83 times, which is indeed beyond the output range. I didn't pay attention to your gain, but only looked at the bottom.

I figured it out. I missed a 1KΩ resistor, which is R13 in the picture. The input-output relationship is what I calculated below.

逐风。

Zhufeng. Posted on 2024-2-5 11:34 Even if I directly give a voltage there and change 1, the output of the op amp will not change

I figured it out. I missed a 1KΩ resistor, which is R13 in the picture. The input-output relationship is what I calculated below.