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Icircuit op amp5/6/2023 Then, the following are true:īecause the input impedance is infinite, all of the current flowing through R 1 (i1) flows through R 2. Figure 1 shows a negative-feedback amplifier (inverting amplifier) using an op-amp. Let’s consider this condition using simple calculations. When the output voltage is finite, there is a very little difference in voltage (virtual short) between the two inputs. The output voltage of a high-gain circuit becomes extremely large in the event of there being a large difference between the two input voltages. The output voltage of an op-amp is equal to its gain multiplied by a difference in voltage between the two inputs. Typical differential amplifiers have a finite output voltage. You can conceptually understand a virtual short as follows. These concepts are helpful for gain calculation. When the input terminal on one side is grounded to GND as shown in the figure, it is sometimes called virtual ground. This condition is met when a negative-feedback circuit is formed using a differential amplifier with a high open-loop gain. This condition is called a virtual short-circuit because the differential inputs have the same voltage even though they are not connected together. A virtual short-circuit (or simply virtual short) refers to a condition of a differential input amplifier such as an op-amp in which its noninverting and inverting inputs have almost the same voltage.
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