we said in the ideal model intensity which is not running for any input terminals of operational amplifier due to the infinite input impedance. Let us consider what happens if this impedance is not infinite. To do this, we consider the problem from two different aspects:
the other possibility is modeled as a resistance differential between the input terminals
If we consider the actual values \u200b\u200bobtained for both cases, we note that Ri-and Ri + are the order of 10 8 , while the values \u200b\u200bof the differential resistance is about 10 6 .
Since this case is more favorable than the other we will focus primarily on him. To do this, consider the following scenario ...
since there is a Rid, this implies that there is an intensity in the amplifier input terminals, which leads to tensions in these terminals are not the same as in the ideal case.
If we consider the intensities plotted on the figure and analyze the circuit get ...
gain Loading ...
multiplying and dividing by R2 ...
Noting the expression obtained is seen to have the same equation in the ideal case to which we added a third term summed in the denominator. This term (R2/ARid) is due to the residual strength and vanishes when it is infinite. If not, a decrease of the gain of the device, but since the values \u200b\u200bfound, their importance is almost always negligible. Therefore, unless otherwise noted, this influences the contempt arem.
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