Electronics > Beginners

Op amp beginner's questions

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bson:
20dBV/decade attenuation is a reciprocal response.  1/10 = 0.1 = -20dB.  Anything of the form 1/f will exhibit it when f changes by 10x.

nsrmagazin:
This is why Schools and Universities exist. You are not going to learn electronics from a forum.

rstofer:

--- Quote from: nsrmagazin on December 03, 2018, 01:48:39 pm ---This is why Schools and Universities exist. You are not going to learn electronics from a forum.

--- End quote ---

To a large extent, that is true.  The theory and the math all tie together and, due to the sequential manner of study, it can't be learned in some random method.  It takes 4-5 years of increasingly more complex math.

OTOH, that's for engineering, not messing around on a breadboard.  We can easily demonstrate filters with a decent DMM (decent in terms of AC response) and a signal source.  My preference for Bode' Plots is the Digilent Analog Discovery 2 but when I was in school, we took individual voltage vs frequency measurements and did the plot by hand.  That's how it was done in the early '70s; we just didn't have the tools we have today.

We can demonstrate transistor circuits fairly easy and a good number of op amp designs really only take a dual rail power supply and some kind of display.  Again, I prefer the AD2 but a scope is workable.  Sometimes even a DMM is adequate.

One of the really nice things about the Internet era is the availability of tutorials on just about any subject.  CalcWorkshop is great (fee required), Khan Academy has an EE track as well as their famous math tutorials and there are a host of other sites (like mathbff or nancypi).  For solvers we have Symbolab and for graphing we have Desmos and there are some really nice offline tools like wxMaxima, Mathematica and even commercial products like MATLAB.

The modern student has it much easier.  All of these tools make learning a lot easier and faster so more time can be spent on theory and less time spent on doing the math.

But it still takes about 5 years to get through an engineering program.

On this topic:  why not build a LPF and measure the output over a couple of decades.  Make the corner frequency fairly low, like 1000 Hz and sweep, by hand, from 100 Hz to 100,000 Hz (3 decades) by hand and PROVE that the roll-off is 20 dB per decade.  Maybe take 10 measurements per decade.  Almost any DMM will handle the low frequency.  Even just 1 decade will prove the roll-off.  A scope is probably required to see the phase shift.

Wimberleytech:

--- Quote from: rstofer on December 03, 2018, 05:34:56 pm ---
....but when I was in school, we took individual voltage vs frequency measurements and did the plot by hand.  That's how it was done in the early '70s; we just didn't have the tools we have today.


--- End quote ---

Indeed...I still have a big folder of semi-log paper of varying numbers of decades.  Beautiful stuff...a certain elegance in plotting those points with a template using a drafting pencil filled with B lead.  But, I am glad we have the tools you mentioned in this modern era.

nsrmagazin:
Like this you leave wholes in the knowledge. A lot of people think that they know something, but in truth they don't. Hope this is not tha case.

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