Op-Amp Inverting vs. Non-Inverting Amplifier: A Comparison

This page compares op-amp inverting amplifiers with non-inverting amplifiers, highlighting the key differences between the two common op-amp circuit configurations.

Op-Amp Inverting Amplifier

The inverting amplifier, as the name suggests, produces an output signal that is inverted (180 degrees out of phase) with respect to the input signal.

Figure 1: Op-Amp Inverting Amplifier Circuit

As shown in Figure 1, the input voltage (either DC or AC) is applied to the inverting (-) terminal of the op-amp through a resistor, typically labeled as $R_{in}$. The non-inverting (+) terminal is connected to ground (0 volts). Negative feedback is implemented using a feedback resistor, $R_f$, which connects the output back to the inverting terminal. This feedback is crucial for stabilizing the amplifier and controlling its gain.

The gain (G) of the inverting amplifier is determined by the ratio of the feedback resistor ($R_f$) to the input resistor ($R_{in}$), and is expressed by the following equation:

$G = \frac{V_{out}}{V_{in}} = -\frac{R_f}{R_{in}}$

The negative sign in the gain equation indicates the inverting nature of the amplifier.

Op-Amp Non-Inverting Amplifier

The non-inverting amplifier, in contrast to the inverting configuration, produces an output signal that is in phase with the input signal.

Figure 2: Op-Amp Non-Inverting Amplifier Circuit

As shown in Figure 2, the input voltage (DC or AC) is applied directly to the non-inverting (+) terminal of the op-amp. A feedback network, consisting of resistors $R_f$ and $R_{in}$, provides negative feedback from the output to the inverting (-) terminal.

The gain of the non-inverting amplifier is also determined by the ratio of the feedback resistor ($R_f$) to the input resistor ($R_{in}$), but the equation is slightly different:

$G = \frac{V_{out}}{V_{in}} = 1 + \frac{R_f}{R_{in}}$

Notice that the gain is always greater than or equal to 1, and there’s no negative sign, indicating that the output is in phase with the input.

Key Differences Summarized