# Non-inverting Amplifier

A non-inverting amplifier produces an amplified signal which has the same polarity as the input signal using only an op-amp IC plus two external resistors

The output voltage is determined by the external resistors and the input voltage according to the following equation:

The voltage gain A_{V} is given by V_{out} / V_{in}, which may be found by rearranging the above expression:

The minimum voltage gain of this circuit is unity, unlike the inverting amplifier which can have a voltage gain either larger or smaller than one. The non-inverting amplifier also benefits from a much higher input impedance than the inverting amplifier.

#### Example 1

Calculate the voltage gain of an non-inverting amplifier with resistors R_{1} and R_{2} = 1 kΩ and 10 kΩ respectively.

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A_{V} = 1 + R_{2} ÷ R_{1}

= 1 + 5,000 ÷ 1,000

= 6

The voltage gain is a number and does not have a unit.

#### Example 2

Calculate the output voltage produced by a non-inverting amplifier if resistor R_{1} = 1 kΩ, feedback resistor R_{2} = 4 kΩ, and the input voltage is +2 V.

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V_{out} = V_{in} × (1 + R_{2} ÷ R_{1})

= 2 × (1 + 4,000 ÷ 1,000)

= 2 × 5

= +10 V