How to calculate gain and phase shift of a Non Inverting Amplifier

[tpc123]

Hi all,

I need to calculate the gain and phase shift of the op amp below but I have no clue how to do it! If anyone can point me in the right direction, that would be great.

I have looked up op amps and can see a lot of info on the web but can't make sense of it because the diagrams and instructions I can find are of amps with two resistors, but this circuit has three so I don't know how to move on.....and my lecturer just had a heart attack so isnt there to help!

To clarify, we have completed an experiment using op amp boards and an oscilliscope to set up this circuit with an input signal of 1kHz and an amplitude of 100mV peak to peak. The frequency was changed in steps from 100 Hz up to 1,000,000 Hz and the Vin, Vout and period were measured then the phase shift and the gain were calculated at each step. I have to present these results and compare them to theoretical results so I need to know how to calculate the gain and phase shift given these perameters.

https://i741.photobucket.com/albums/xx55/tpc3dsm/opamp.jpg

Any help would be great!! Thanks in advance

 

[mneary]

That isn't a non inverting amplifier.

When you have an accurate schematic, download LTSpice from htp://www.linear.com. It is an excellent spice based simulator.

 

[tpc123]

OK...I guess you can see that I know absolutely nothing about electronics! That is the circuit we set up though so any clues as to what it is if not a non inverting amplifier?

 

[mneary]

What did you build and test?

 

[tpc123]

It was definitely that circuit. On the worksheet we were given it says its a non-inverting amplifier and gives us that image then goes on to tell us to set up the circuit on the op amp board (DG2X34), set the input signal & amplitude and set the Vin with a frequency meter then obtain the Vout & period from the oscilliscope then calculate the gain and phase shift. I have done all of this without any trouble. It is just the theory I am having trouble with....and now you say its not actually a non-inverting amp.....and I cant get help from uni.....and I am starting to panic....just a bit!

 

[Hero999]

At low gains and frequencies the gain is equal to the following formula:

[latex]Av = 1+\frac{R_f}{R_g}[/latex]

**broken link removed**

And the the phase shift will be near zero.

At higher frequencies the gain will drop and the phase shift will lag. Without knowing what op-amp you're using, there's no way to calculate this. The easiest way is by looking at the bode plot on the datasheet for the op-amp you're using but you've not told us what it is or given the datasheet so we don't know.

 

[audioguru]

You have the (+) and (-) symbols for the inputs of the opamp mixed up. Pin2 is (-) and pin3 is (+).
An opamp has an extremely high input resistance so the input resistor is doing nothing and can be replaced with a piece of wire.
The other two resistors set the low frequency gain of the opamp as shown by HERO.

 

[mneary]

It was definitely that circuit.

If it worked, it was NOT the circuit that you posted.

That circuit is similar to a non-inverting amplifier but the + and - inputs to the op amp are swapped. Possibly one of your lab partners fixed it without saying?