How does an op amp work? How does it “see” the feedback voltage?

Question

How does an op amp work? How does it “see” the feedback voltage?

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Answer 1

Tldr: An op amp is a device that amplifies the difference between two input voltages. The feedback voltage is the voltage that is fed back from the output to one of the inputs. The feedback voltage can be negative or positive, depending on how it is connected to the inputs. The op amp “sees” the feedback voltage through its inputs and tries to make them equal by adjusting its output voltage.

An op amp has two inputs: one is called the **inverting input** (marked with a – sign) and the other is called the **non-inverting input** (marked with a + sign). It also has one output that can produce either a positive or negative voltage.

The feedback voltage is the voltage that is fed back from the output to one of the inputs, usually through a resistor or a capacitor. The feedback voltage can affect the gain and stability of the op amp circuit. There are two types of feedback: **negative feedback** and **positive feedback**.

Negative feedback is when the feedback voltage is in opposite phase to the input voltage. This means that the feedback voltage reduces the difference between the two input voltages, and thus reduces the output voltage. Negative feedback can make the op amp circuit more stable, accurate and linear.

Positive feedback is when the feedback voltage is in phase with the input voltage. This means that the feedback voltage increases the difference between the two input voltages, and thus increases the output voltage. Positive feedback can make the op amp circuit unstable, oscillate or saturate.

The op amp “sees” the feedback voltage through its inputs. The op amp compares the voltages at its two inputs and tries to make them equal by adjusting its output voltage. If the feedback voltage is connected to the inverting input, the op amp will try to make its output voltage opposite to the input voltage. If the feedback voltage is connected to the non-inverting input, the op amp will try to make its output voltage same as the input voltage.