why does negative feedback do not work?

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mohamis288

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Hello,

here is my circuit which is implementing negative feedback. the input is just a sine wave with DC level of 300m V and amplitude of 200m V:




our opamp is ideal. But when I simulate it, opamp negative lead represents the following plot:


it is weird. why? I expect ot to be constant all over the simulation time. it seems so that sine generator is connected to opamp negative lead. How can I avoid this to happen?
 

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Your circuit is an integrator, so any DC error will make the output
center-point drift. That error can / does include Vio.
 

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dick_freebird said:
Your circuit is an integrator, so any DC error will make the output
center-point drift. That error can / does include Vio.
Click to expand...
You know I want to use this integrator in my dual slope ADC. so, I should solve this problem in a way. I want negative lead to be constant. Is there any solution?
 

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No stable operation point without some negative DC feedback. You can make a lossy integrator my placing a high-ohmic resistor parallel to capacitor.
 
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