Simple question about inverting and noninverting op amp amplifiers

In summary, the conversation discusses the use of inverting and noninverting amplifiers, and whether the input can be connected to the opposite terminal. The expert summarizer explains that the phase of the output is different depending on which terminal is used and that for a digital NOT gate, the phase is always 180 degrees from the input. They also mention the importance of the loop gain and how switching the terminals can result in positive feedback and instability. Ultimately, the answer is that the circuit will not work if the terminals are switched.
  • #1
learningphysics
Homework Helper
4,098
7
Hi. I've always seen inverting amplifiers with the input going to the negative terminal of the op amp, and noninverting amplifiers with the input going to the positive terminal. However I don't see any reason why the inverting amplifier couldn't be used exactly the same way with the input going to the positive terminal, and noninverting with the input going to the negative terminal (but I've never seen it like this). Am I wrong?

Is there a reason the design is the way it is? Thanks.
 
Engineering news on Phys.org
  • #2
I am not entirely sure what your question is.
For the - input the phase of the output is 180 degrees from the input.
For the + input the phase is the same.

If you do not care about the phase then either the + or - terminal can be used.
If you do not care about the phase then you do not care about inverting or noninverting.

For a digital NOT gate phase of the output is 180 degrees from the input.
This is the meaning of inverting.
 
  • #3
By inverting amplifiers, I was referring to this circuit:http://cnx.rice.edu/content/m0055/latest/
not the inverting terminal. I was wondering if the circuit would work if you had the positive terminal at the top and negative at the bottom. Anyway I think I found the answer, it won't work. The loop gain BA must be >0 to ensure negative feedback. If the terminals are switched BA becomes <0 which means positive feedback and instability.
 
Last edited by a moderator:

1. What is the purpose of an inverting and noninverting op amp amplifier?

An op amp amplifier is designed to amplify an input signal to a higher level. An inverting op amp amplifier inverts the input signal and amplifies it while a noninverting op amp amplifier amplifies the input signal without inverting it.

2. How does an inverting op amp amplifier work?

An inverting op amp amplifier has an input connected to the inverting input terminal of the op amp and a feedback resistor connected between the output and the inverting input. The amplified output is then fed back to the inverting input, creating a closed-loop circuit. The gain of the amplifier is determined by the ratio of the feedback resistor to the input resistor.

3. What is the difference between the gain of an inverting and noninverting op amp amplifier?

The gain of an inverting op amp amplifier is determined by the ratio of the feedback resistor to the input resistor, while the gain of a noninverting op amp amplifier is determined by the ratio of the feedback resistor to the sum of the feedback resistor and the input resistor. This means that the gain of a noninverting op amp amplifier is always greater than or equal to 1, while the gain of an inverting op amp amplifier can be less than or equal to 1.

4. Can the input and feedback resistors be interchanged in an inverting op amp amplifier?

No, the input and feedback resistors cannot be interchanged in an inverting op amp amplifier. The input resistor must always be connected between the input signal and the inverting input terminal of the op amp, while the feedback resistor must always be connected between the output and the inverting input terminal.

5. What are the applications of inverting and noninverting op amp amplifiers?

Inverting and noninverting op amp amplifiers are commonly used in signal processing, audio amplification, and sensor circuits. Inverting amplifiers are also used in inverting power supply circuits to create a negative output voltage. Noninverting amplifiers are often used in voltage follower circuits to isolate the input signal from the output.

Similar threads

  • Electrical Engineering
3
Replies
78
Views
13K
Replies
5
Views
2K
  • Electrical Engineering
Replies
3
Views
745
  • Electrical Engineering
Replies
6
Views
1K
  • Electrical Engineering
Replies
3
Views
1K
  • Electrical Engineering
Replies
11
Views
2K
  • Electrical Engineering
Replies
15
Views
2K
  • Electrical Engineering
Replies
6
Views
1K
Replies
5
Views
2K
  • Electrical Engineering
Replies
3
Views
1K
Back
Top