Inverting Amplifier vs. Non-Inverting Amplifier

Attribute	Inverting Amplifier	Non-Inverting Amplifier
Input impedance	High	High
Output impedance	Low	Low
Gain	Negative	Positive
Input signal phase	Inverted	Non-inverted
Input voltage	Can be both positive and negative	Positive only
Feedback resistor	Connected between the input and the inverting terminal	Connected between the input and the non-inverting terminal
Input resistor	Connected between the inverting terminal and ground	Connected between the non-inverting terminal and ground
Output voltage	Amplified and inverted	Amplified and non-inverted

Introduction

Amplifiers are essential components in electronic circuits that increase the amplitude of an input signal. Inverting and non-inverting amplifiers are two common types of operational amplifiers (op-amps) used in various applications. While both amplifiers serve the purpose of amplification, they differ in terms of their input and output characteristics, gain, and overall circuit configuration. In this article, we will explore the attributes of inverting and non-inverting amplifiers, highlighting their similarities and differences.

Inverting Amplifier

The inverting amplifier is a configuration where the input signal is applied to the inverting terminal of the op-amp. This means that the input signal is connected to the inverting input terminal, while the non-inverting input terminal is grounded. The output signal is taken from the junction of the resistor connected to the inverting input and the feedback resistor. The gain of the inverting amplifier is determined by the ratio of the feedback resistor to the input resistor.

One of the key advantages of the inverting amplifier is its ability to provide a stable and predictable gain. The gain is determined solely by the ratio of the resistors, making it easy to adjust and control. Additionally, the inverting amplifier has a high input impedance, which means it does not load the input signal source. This makes it suitable for applications where the input signal source has a high output impedance.

However, the inverting amplifier also has some limitations. Since the input signal is applied to the inverting terminal, the output signal is phase-inverted compared to the input signal. This means that the output signal is 180 degrees out of phase with the input signal. While this may not be an issue in some applications, it can cause problems in others, especially when dealing with feedback systems or signal processing.

Another limitation of the inverting amplifier is that it requires a negative power supply. This is because the op-amp needs a negative voltage reference to operate properly. This can add complexity to the overall circuit design and may require additional components such as a dual power supply or a voltage inverter.

In summary, the inverting amplifier offers a stable gain and high input impedance, but it produces a phase-inverted output signal and requires a negative power supply.

Non-Inverting Amplifier

The non-inverting amplifier is a configuration where the input signal is applied to the non-inverting terminal of the op-amp. This means that the input signal is connected to the non-inverting input terminal, while the inverting input terminal is grounded. The output signal is taken directly from the output terminal of the op-amp. The gain of the non-inverting amplifier is determined by the ratio of the feedback resistor to the input resistor.

One of the main advantages of the non-inverting amplifier is that it does not invert the phase of the input signal. This makes it suitable for applications where maintaining the phase relationship between the input and output signals is critical, such as audio amplification or signal processing. Additionally, the non-inverting amplifier has a high input impedance, similar to the inverting amplifier, which ensures that it does not load the input signal source.

However, the non-inverting amplifier also has some limitations. Unlike the inverting amplifier, the non-inverting amplifier has a lower input impedance due to the presence of the input resistor. This can affect the overall performance of the amplifier, especially when dealing with high-frequency signals or low-impedance input sources. Additionally, the non-inverting amplifier may require a positive power supply, depending on the specific op-amp used.

Another limitation of the non-inverting amplifier is that it may introduce a small amount of voltage offset. This voltage offset can cause inaccuracies in the amplified output signal, especially when dealing with low-level signals or precision applications. However, this can be mitigated by using op-amps with low input offset voltage or by employing additional circuitry to compensate for the offset.

In summary, the non-inverting amplifier provides a non-inverted output signal and has a high input impedance, but it has a lower input impedance compared to the inverting amplifier and may introduce a voltage offset.

Comparison

Now that we have explored the attributes of both inverting and non-inverting amplifiers, let's compare them side by side:

Input Configuration

• Inverting Amplifier: The input signal is applied to the inverting terminal of the op-amp.
• Non-Inverting Amplifier: The input signal is applied to the non-inverting terminal of the op-amp.

Output Configuration

• Inverting Amplifier: The output signal is taken from the junction of the resistor connected to the inverting input and the feedback resistor.
• Non-Inverting Amplifier: The output signal is taken directly from the output terminal of the op-amp.

Gain

• Inverting Amplifier: The gain is determined by the ratio of the feedback resistor to the input resistor.
• Non-Inverting Amplifier: The gain is determined by the ratio of the feedback resistor to the input resistor.

Phase Relationship

• Inverting Amplifier: The output signal is phase-inverted compared to the input signal.
• Non-Inverting Amplifier: The output signal is non-inverted compared to the input signal.

Input Impedance

• Inverting Amplifier: The inverting amplifier has a high input impedance, which ensures that it does not load the input signal source.
• Non-Inverting Amplifier: The non-inverting amplifier also has a high input impedance, similar to the inverting amplifier.

Power Supply

• Inverting Amplifier: The inverting amplifier requires a negative power supply.
• Non-Inverting Amplifier: The non-inverting amplifier may require a positive power supply, depending on the specific op-amp used.

Limitations

• Inverting Amplifier: The inverting amplifier produces a phase-inverted output signal and requires a negative power supply.
• Non-Inverting Amplifier: The non-inverting amplifier has a lower input impedance compared to the inverting amplifier and may introduce a voltage offset.

Conclusion

In conclusion, both inverting and non-inverting amplifiers have their own set of attributes and limitations. The choice between the two depends on the specific requirements of the application. If maintaining the phase relationship between the input and output signals is critical, the non-inverting amplifier is a suitable choice. On the other hand, if a stable gain and high input impedance are desired, the inverting amplifier is a better option. It is important to carefully consider the trade-offs and select the amplifier configuration that best meets the needs of the circuit design.