- Non-Inverting Amplifier Definition: A non-inverting amplifier is an op-amp that outputs a signal with the same polarity as the input, ensuring the gain is always positive.
- Input Terminals Explained: The non-inverting input (+) receives the signal and amplifies it without reversing its polarity, essential for preserving the original signal characteristics.
- Gain Formula: The gain of a non-inverting amplifier is determined by the ratio of feedback resistance to input resistance, crucial for setting the amplification level.
- Unity Gain Importance: In unity gain configuration, the amplifier acts as a voltage follower, providing high impedance isolation between circuits without altering the signal.
- Practical Utility: Non-inverting amplifiers are widely used in electronics to boost signal power while maintaining signal integrity, ideal for complex electronic systems.
A non-inverting amplifier is defined as an operational amplifier that amplifies input signals without reversing their polarity, resulting in a positive voltage gain.
A non-inverting operational amplifier or non-inverting op-amp uses an op-amp as the main element.
An op amp features two input terminals: the inverting input marked with a minus sign (-) and the non-inverting input marked with a plus sign (+).
Applying a signal to the non-inverting input results in an amplified output that retains the original signal’s polarity.
Consequently, the gain from a non-inverting amplifier configuration is invariably positive.
Let us explain the thing by constructing the op-amp circuit with the feedback loop as shown below,
Here, in the above circuit, we connect an external resistance R1 and feedback resistance Rf at inverting input. Now, by applying Kirchhoff Current Law, we get,
Let us assume the input voltage applied to the non-inverting terminal is vi.
Now, if we assume that the op-amp in the circuit is ideal op-amp, then,
Therefore, equation (i) can be rewritten as,
The closed-loop gain of the circuit is,
This term does not contain any negative parts. Hence, it proves that the input signal to the circuit gets amplified without changing its polarity at the output.
From the expression of the voltage gain of a non-inverting op-amp, it is clear that the gain will be unity when Rf = 0 or R1 → ∝.
So, if we short circuit the feedback path and/or open the external resistance of the inverting pin, the gain of the circuit becomes 1.
This circuit is called a voltage follower or unity gain amplifier. This is used to isolate two cascaded circuits, because of its infinitely large impedance, at op-amp inputs.
