Inverting Op Amps vs. Non-Inverting Op Amps

Attribute	Inverting Op Amps	Non-Inverting Op Amps
Input impedance	High	High
Gain	-Rf/R1	1 + Rf/R1
Phase shift	180 degrees	0 degrees
Input bias current	Low	Low
Input offset voltage	Low	Low

Introduction

Op amps, or operational amplifiers, are essential components in electronic circuits. They are widely used for amplification, filtering, and signal processing. Inverting and non-inverting op amps are two common configurations that have distinct attributes and applications. Understanding the differences between these two types of op amps is crucial for designing and analyzing circuits effectively.

Input and Output

In an inverting op amp configuration, the input signal is applied to the inverting terminal (-) of the op amp, while the non-inverting terminal (+) is connected to ground. The output signal is inverted with respect to the input signal, hence the name "inverting op amp." On the other hand, in a non-inverting op amp configuration, the input signal is applied to the non-inverting terminal (+), and the output signal is in phase with the input signal. This difference in input and output connections results in distinct behaviors for inverting and non-inverting op amps.

Gain

One of the key differences between inverting and non-inverting op amps is the gain of the amplifier. In an inverting op amp configuration, the gain is determined by the ratio of the feedback resistor to the input resistor. The gain is negative in this configuration, meaning that the output signal is inverted and amplified. On the other hand, in a non-inverting op amp configuration, the gain is determined by the ratio of two resistors in the feedback loop. The gain is positive in this configuration, resulting in an output signal that is in phase with the input signal.

Input Impedance

Another important attribute to consider when comparing inverting and non-inverting op amps is input impedance. In an inverting op amp configuration, the input impedance is determined by the input resistor connected to the inverting terminal. This resistor forms a voltage divider with the input signal, affecting the input impedance of the amplifier. In a non-inverting op amp configuration, the input impedance is determined by the input resistor connected to the non-inverting terminal. The input impedance in this configuration is typically higher compared to the inverting configuration.

Common Mode Rejection Ratio

The common mode rejection ratio (CMRR) is a measure of an op amp's ability to reject common mode signals present at both input terminals. In an inverting op amp configuration, the CMRR is typically lower compared to a non-inverting configuration. This is because the inverting op amp amplifies the common mode signal along with the differential signal, leading to a lower CMRR. On the other hand, a non-inverting op amp configuration provides better CMRR due to the differential input and output signals being in phase.

Frequency Response

The frequency response of an op amp is an important consideration in many applications, especially in signal processing and filtering circuits. Inverting op amps typically have a higher bandwidth compared to non-inverting op amps. This is because the inverting configuration has a single-pole response, which allows for higher frequency operation. On the other hand, non-inverting op amps have a two-pole response, which limits the bandwidth of the amplifier. This difference in frequency response can impact the performance of the op amp in various applications.

Applications

Both inverting and non-inverting op amps have specific applications where they excel. Inverting op amps are commonly used in inverting amplifiers, summing amplifiers, and active filters. The inverted output signal is useful in applications where phase inversion is required. On the other hand, non-inverting op amps are often used in voltage followers, buffer amplifiers, and voltage regulators. The non-inverted output signal is beneficial in applications where preserving the phase of the input signal is important.

Noise Performance

Noise performance is another important factor to consider when comparing inverting and non-inverting op amps. In general, inverting op amps have better noise performance compared to non-inverting op amps. This is because the inverting configuration provides better common mode rejection, which helps reduce noise in the output signal. On the other hand, non-inverting op amps may be more susceptible to noise due to their lower common mode rejection ratio. Designers should carefully consider the noise performance requirements of their circuit when choosing between inverting and non-inverting op amps.

Conclusion

In conclusion, inverting and non-inverting op amps have distinct attributes and applications that make them suitable for different circuit designs. Understanding the differences in input and output connections, gain, input impedance, CMRR, frequency response, applications, and noise performance is essential for selecting the right op amp configuration for a given circuit. By considering these factors carefully, designers can optimize the performance of their circuits and achieve the desired functionality.