Basic opamp inverter

[EngIntoHW]

Hi,

I don't understand how does this opamp work in this configuration.
Like, how is the output related to the input.
Could anyone explain how it works?

Thanks.

 

[canadaelk]

Google: unity gain buffer

 

[KeepItSimpleStupid]

An OP amp basically takes two voltages and multiplies them by a BIG number (open loop gain). If the noon-invering input is A and the inverting B, then the output is (A-B)G where G is a big number.

Another way of looking at this is that with negative feedback, the A and B terminals will try to be the same voltage. So, in order for A and B to be the same, A must equal B.

These concepts can easily help you understand an inverting amplifier as well.

 

[Grossel]

I'll try to explain this on another way.

When positive terminal is higher (always in terms of voltages), the output will rise until it reach a voltage close to positive voltage terminal. And opposite happends when polarity on input changes. This goes very fast, but let's say it doesn't (more easy to explain then).

When connected as this, let's assume time t0, the moment you switch on power.
Let's assume there is always 2V on positive terminal, regardless if power is on or not (just to make it easier).
There is many different opamps models, so we also need to assume that output voltage is zeero the moment after power is applied to circuit (in real life it can be everything).

Power is on and situation is that negative input follows output, always. This is now 0V (assumption).
Positive terminal is 2V, wich is higher. Therefore the output rises.
When output reach the same voltage as positive input, the speed of the voltage rise slow down.
But because of delays, output voltage will swing a little bit above positive input voltage.
Now, the opamp detects that negative input (remember: still connected to output) is slightly higher, so the output start decreasing voltage.

And the swinging will continue until it sets at same voltage as on positive input.

 

[EngIntoHW]

Thanks a lot mates.
Especially to you Grossel, for a great explanation

 

[crutschow]

Hi,

I don't understand how does this opamp work in this configuration.
Like, how is the output related to the input.
Could anyone explain how it works?

Thanks.

This is a non-inverter (follower) not an inverter.

 

[audioguru]

Some people call a logic inverter a "NOT Gate".
They might also call this opamp follower a "NOT Amplifier".