Inverting Operational amplifier

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In an inverting operational amplifier configuration with R1 at 1000 ohms and Rf at 1,000,000 ohms, the input impedance is equal to R1, which is 1000 ohms, while the output impedance is considered to be zero. In contrast, a non-inverting operational amplifier with R1 at 3500 ohms and Rf at 15000 ohms theoretically has infinite input impedance, but this is only true for ideal op-amps. For real op-amps, the input impedance typically ranges from 1 MΩ to 10 TΩ. The discussion raises the question of whether R1 can be considered the input impedance for both configurations. Understanding these impedance characteristics is crucial for designing circuits using operational amplifiers.
Amith2006
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Homework Statement


1) Consider an inverting operational amplifier as shown in figure. Suppose R1= 1000 ohm & Rf = 10^6 ohm. It is said that the input impedance=R1=1000 ohm and the Output impedance= 0.

2) Consider a non inverting operational amplifier as shown in figure. Suppose R1= 3500 ohm & Rf = 15000 ohm. It is said that the input impedance=infinite. Why is it so? Here Rf is the feedback resistor.But only for an ideal Op-Amp, the input impedance is infinite and not for a real one, isn’t it? So, can R1 be taken as the input impedance of the Op-Amp in both cases?


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These are a couple of links that explain the input impedance for both op amps.
http://www.phys.uAlberta.ca/~gingrich/phys395/notes/node102.html
http://www.phys.uAlberta.ca/~gingrich/phys395/notes/node103.html

For a real non inverting op amp, the input impedance is somewhere between 1 MΩ to 10 TΩ.
 
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