Non Inverting Vs Inverting Op Amp

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

Understanding operational amplifiers (op-amps) is crucial for anyone working with analog electronics. A key aspect of op-amp circuits lies in the configuration: inverting and non-inverting. This article delves into the differences between these two fundamental configurations, explaining their characteristics, applications, and helping you choose the right one for your project.

The core difference lies in how the input signal affects the output signal's phase. In an inverting configuration, a positive input results in a negative output, and vice versa. Conversely, the non-inverting configuration maintains the input signal's polarity at the output. Let's examine each in detail.

Inverting Op Amp Configuration

In the inverting configuration, the input signal is applied to the inverting terminal (-) of the op-amp, while the non-inverting terminal (+) is grounded. A feedback resistor (Rf) connects the output to the inverting input, forming a negative feedback loop.

Characteristics:

• Gain: The gain is determined by the ratio of the feedback resistor (Rf) to the input resistor (Ri): Gain = -Rf/Ri. The negative sign indicates the phase inversion.
• Input Impedance: Relatively low input impedance, typically equal to the value of the input resistor (Ri).
• Output Impedance: Low output impedance.
• Applications: Commonly used as voltage amplifiers, inverting buffers, and in subtractor circuits. It's ideal when phase inversion is acceptable or even desired.

Non-Inverting Op Amp Configuration

The non-inverting configuration applies the input signal to the non-inverting terminal (+), while the inverting terminal (-) is connected to the feedback network. A feedback resistor (Rf) and an input resistor (Ri) are usually employed.

Characteristics:

• Gain: The gain is given by the formula: Gain = 1 + (Rf/Ri). Note the absence of a negative sign.
• Input Impedance: Very high input impedance, making it ideal for applications where minimal loading of the input source is necessary.
• Output Impedance: Low output impedance.
• Applications: Widely used as voltage followers (buffers), voltage amplifiers requiring no phase inversion, and in instrumentation amplifiers.

Head-to-Head Comparison: Inverting vs. Non-Inverting

Choosing the Right Configuration

The best configuration depends on your specific needs. Consider the following:

• Required Gain: Need a specific gain? Both configurations offer precise gain control through resistor selection. Remember the different gain equations.
• Phase Inversion: Is phase inversion acceptable or undesirable? This directly dictates your choice.
• Input Impedance: Will the input source be significantly loaded by the op-amp? A high input impedance is crucial for sensitive sources.
• Application: Certain applications, like voltage followers, inherently demand the non-inverting configuration.

By understanding the nuances of inverting and non-inverting op-amp configurations, you can design and build effective analog circuits tailored to your application. Remember to consider the specific characteristics of each configuration when choosing the appropriate design for your project. This knowledge is foundational to many more complex analog circuit designs.