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Negative feedback to opamp

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predator89

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I have designed a negative feedback opamp. My output from the opamp is high voltage AC which i am feeding back to low voltage differential amplifier stage with ICMR 0 to 3 V.
My doubt is that if i try giving the negative feedback, the MOS connected to the positive terminal is cut off as the positive terminal is grounded.
So what is the proper way to give feedback? Pls Help!!
 

Most opamps can produce an output voltage swing of almost the entire supply voltage. Their allowed input voltage range includes the entire supply voltage so that negative feedback can produce a gain as low as 1.

Why does your opamp with a high voltage output swing have an input with low voltage input rating?
 

Actually i am designing a HV operational amplifier in cadance. The problem is that when I give negative feedback to my design, the MOS with positive terminal from diff amp is grounded for feedback. Due to this this MOS goes in cut off. So is this operation correct? As it changes the baising of my entire design.
 

I do not understand how a MOS input that is grounded is used for feedback without seeing the schematic and its powering (plus and minus or single?).
When the positive input of an opamp is grounded then the opamp is inverting and has a positive and negative supply so the inputs are biased correctly.
 

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when it is said that the positive terminal is grounded, it means the positive terminal is at ground for AC signals. But it should be biased at proper DC voltage in order for correct operation.

In your case, you should make sure the positive and negative terminals of the opamp are at same DC potential. (i.e when there is no signal)
 
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