Go Down

### Topic: Building an Audio Analyzer with Matrices and Mega2560 / Uno and FFT and Op amps (Read 9172 times)previous topic - next topic

#### dhenry

Quote
I know how to get a gain lower, using negative feedback.

Again, name your favorite opamp and I can show you how to get its open loop gain down to 1x (or any number you wish to have).

No negative feedback. How's that?

All you need to do is to  name your favorite opamp.

#### Magician

If you don't know what logarithm means, there are some books available:
http://www.dummies.com/store/Education/Math.html

#### dhenry

Again, just name your favorite opamp and I can show its gain < 1x (or 200x if you prefer), without using negative feedback.

Does that make your favorite opamp not an opamp?

#### Papa G

Okay, I'll play, configure a 741 op-amp for a DC open loop gain of 1 with no external components.

The LM386 is not an op-amp. It is a PGA at best.

#### Aaron_dyer

Ok damn guys....this isn't a see who pees farther contest...

I'm an Electronics Engineer as well.

I will say my favorite op amp to use is the LM358 but if I'm using one for multiple I/Os, I would use the LM3900.....However since I'm trying to tackle my original question.....using FFT to calculate a good audio analyzer output interfaced by the arduino...I know its possible and using the LM386 (Low power audio Amp) is what I have in mind.....

I hate op amps that need that negative supply i.e.  741

I just don't want negative gain I know that much so interfacing either amp via its non -inverting input  (Rf / Ri) + 1 = Av (Gain)

now interfacing its output to the arduino via an analog Input and then interfacing that to maybe some LED drivers (Max7219s) to drive LED matrices......

#### dhenry

Quote
I hate op amps that need that negative supply i.e.  741

There are many ways to use an opamp in single rail application - the devices don't care whether it is used in dual rail or single rail. All it cares about is differential potentials so there is current float.

Issues come around in interfacing with signals referenced differently. The dual rail solution happens to be the simplest in that department.

#### Aaron_dyer

I know what you're saying....I would much rather deal with those types in your more used comparators, integrators, differentiators, summing.....etc.

I watched the rainbow tears video....neat project, but not exactly what I'm looking for...

Go Up