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llbaobao
Joined: 19 May 2008
Posts: 51
Helped: 5
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 30 Oct 2009 8:48 what is the feedback type of the inverting amp? |
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Though I have read the feedback chapter in books, still I can not analysis it.
The simplest inverting amp use what kinds of feedback?
volt-volt feedback? current-volt feedback? or others?
Please help me.
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LvW
Joined: 07 May 2008
Posts: 1466
Helped: 242
Location: Germany
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30 Oct 2009 11:34 Re: what is the feedback type of the inverting amp? |
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The inverting opamp applies voltage controlled current feedback.
Explanation: The input parameter of the inverting opamp must be regarded as a current (because the voltage is not applied directly at the input pin but via R1) - and this current is superimposed with another current driven by the output voltage via R2.
As a result - two currents are added at the inverting input node and create a voltage which is very small (mikrovolts) and which is amplified by the open loop gain.
Thereby, the input resistance of the whole circuit goes down to a value which is app. identical to r1.
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llbaobao
Joined: 19 May 2008
Posts: 51
Helped: 5
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30 Oct 2009 12:22 what is the feedback type of the inverting amp? |
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thank you very much!
Though I have studied many theories, I can not use them freely.
Thank you.
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