Electronics > Beginners
It's not easy being a beginner........
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rstofer:
This particular subject, square waves into a bandwidth limited scope, is going to take a while to truly understand.  The math of the Fourier Series is a bit tedious and not at all important at this point.

The short version: A square wave is composed of a series of sine waves at odd harmonics (1st (fundamental), 3rd, 5th...) from DC to daylight (a really high frequency).  The amplitude of each sine wave is related to 1/n where n is the harmonic number.  As a result, by the time we get to the 9th harmonic, we're talking about a relatively small but nonzero contribution.

So, take a 100 MHz square wave and put it through a 100 MHz scope.  All you will see is a 100 MHz sine wave because the next harmonic is the 3rd (300 MHz) and that will never make it through the analog front end of the scope.  You absolutely won't have any 5th harmonic.  So all you see is the 1st harmonic, a sine wave at 100 MHz.

Repeat the experiment with a 10 MHz square wave and it will look pretty good because the 9th harmonic will pass through the front end.

Attached is the output from the Analog Discovery Spectrum tool.  It shows the spectrum of a 2V p-p square wave of 1 kHz that is symmetric with 0V (+1 to -1).  As a result, there is no spike at 0 Hz (the DC offset that would be present if the signal was 0V to 2V) and it shows the contributions out to the 19th harmonic and the amplitude is still not 0.

This is a five minute experiment with the Analog Discovery 2 which is why I think so highly of it.

At this point it is sufficient to know that you can't see a 100 MHz square wave on a 100 MHz scope.
Paul Moir:

--- Quote from: tautech on October 17, 2019, 08:58:12 am ---And they're called Robertson drives.
https://en.wikipedia.org/wiki/P._L._Robertson

--- End quote ---

Being a bit pedantic here, but a square drive is not a Robertson.  A Roberson is a trapazoid truncated pyramid, which is what makes it awesome, while square drive and Allen are not and therefore not awesome.  Think lathe key.   (For Noidzoid's sake:  Canadians are a little patriotic about our screw.  While the rest of the world foolishly ignores them, you'll find them ubiquitous here.)

Dave:

--- Quote from: konzill on October 14, 2019, 08:29:10 pm ---I decided to go with The Art of Electronics for my main book.  Turns out it goes through things at breakneck speed and does not always do a great job of explaining them.

As an example its explanation of Thévenin's Theorem left me completely confused.  I guess its really meant to be used in a University setting where you are also attending lectures.

--- End quote ---
The vast majority of The Art of Electronics is layman level stuff. It's a 1200 page book, there is only so much they can pack into it.
Noidzoid:

--- Quote from: Paul Moir on October 18, 2019, 03:10:17 am ---
--- Quote from: tautech on October 17, 2019, 08:58:12 am ---And they're called Robertson drives.
https://en.wikipedia.org/wiki/P._L._Robertson

--- End quote ---

Being a bit pedantic here, but a square drive is not a Robertson.  A Roberson is a trapazoid truncated pyramid, which is what makes it awesome, while square drive and Allen are not and therefore not awesome.  Think lathe key.   (For Noidzoid's sake:  Canadians are a little patriotic about our screw.  While the rest of the world foolishly ignores them, you'll find them ubiquitous here.)

--- End quote ---

I do believe they are used in some differential plugs.  Excellent as the key doesn't jam in the hole. Name not known to me as Robertson (unit now) but well aware the use. And yes, lathe keys rarely get stuck unless something fouls it.  Nothing wrong with your well placed pride for your  countryman it is an excellent design.
StillTrying:

--- Quote from: Dave on October 18, 2019, 06:00:39 am ---The vast majority of The Art of Electronics is layman level stuff.

--- End quote ---

I think you could get quite far just knowing all of AoE's subjects in layman's terms.


--- Quote ---It's a 1200 page book, there is only so much they can pack into it.
--- End quote ---

Is it just me that can think of at least 3 solutions to the only 1200 pages problem. :)
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