Suggestions for Fundamental Friday

[AnalogFever]

First off, many thanks to Dave for his excellent takeoff on the first FF episode.  It is very well done, smooth, and informative. 

I am wondering if Dave can do lectures on various bridges used in analog electronics such as Wheatstone bridge, Wien bridge, and Maxwell bridge just to mention a few.

Of particular interest to me is the Wien bridge as I am trying to understand how this bridge is being used with rejection amplifier and bridge amplifier to null out the fundamental frequency in the HP334 Distortion Analyzer.

I think these bridge circuits are great gems of analog circuitry as they were also used to measure the value of an unknown component like an inductor, before the digital meters became popular.  I think there are other applications as well, so I am fairly confident that these would make for very good Fundamental Friday materials. 

Once again, thank you Dave and I look forward to see what you have in store for us.

[Strada916]

And for the more advanced how about

Intergrater circuits and there uses.
dv/dt circuits and there uses.

And for a little more advanced.
La Pace Transforms and how they are implemented in electronics.
Fast Fourier Transforms also how they are implemented in electronics.

[jmole]

I want to see a confirmation, or a rebuttal of this video:

[pickle9000]

Electronics safety, not the rules but the concept.

This is one of the best descriptions I have seen, and yes it involves ohms law. Of particular interest if the table that shows how dangerous punctured skin can be.

http://www.mpoweruk.com/shock.htm

I know this stuff but think there are many who do not.

[NiHaoMike]

What about sine wave vs. square wave inverters in motor drives? For a physical example, you could compare one of those Noctua fans (sine wave drive) against an el cheapo fan of the same size and power rating (square wave drive). Maybe even cover DSP drives that can dynamically vary the waveform based on operating conditions. (The Cindy Wu DSP drive technology in some high end Delta fans uses sine waves at low speeds for quietness and trapezoid waves at high speed for power.)

[Corporate666]

If we are talking about fundamentals, what about the big one... transistors.  BJT's, FET's, IGBT's, diode drops, gate capacitances, Rds, level shifting, switching FET's with BJT's, unique uses for FET's (overvoltage protection, polarity protection, etc).

It's an interesting topic, IMO, and many of the tutorials out there are either way too simplistic or massively overcomplicated with tons of math and dry minutia that puts you to sleep.  There are so many examples that could be done as well.



Another idea is EMI... what is it, what causes it, how to measure it, how can you avoid generating it through circuit layout or make your circuits less susceptible to it, or how yo mitigate it (i.e. snubbers).  I bet a lot of people see that metallized spray on the inside of an enclosure and wonder "why do they do that, how does it work and what's the point?".

[AndyC_772]

I'd vote for something on high speed switching, decoupling, and why a breadboard is such an awful way to try and build a logic circuit that will work reliably. Talk a bit about power distribution, switching current and the effect of inductance in the supply lines, the benefits of using termination resistors and solid ground power planes, and about why you sometimes see double clocking when two chips are joined together over a distance.

[Skimask]

How about a F.F. all about how to ask smart questions?

nah...that would take days, possibly weeks to drill into some people's heads...

[Rerouter]

feedback loop stability? its not really as fundamental, but a topic not many of us understand, and very important in most circuits...

e.g. pole and zero compensation, bandwidth limiting, etc,.

[justanothercanuck]

One topic that comes up every now and again in one place I frequent is "how do I choose an op-amp?"... 

[TerminalJack505]

feedback loop stability? its not really as fundamental, but a topic not many of us understand, and very important in most circuits...

e.g. pole and zero compensation, bandwidth limiting, etc,.

+1   

[codeboy2k]

One topic that comes up every now and again in one place I frequent is "how do I choose an op-amp?"... 

Yes, that would make a good video topic, because it can be a place to discuss the datasheet information.

my answer: more often than not, I have a specific characteristic that is important for a specific opamp in a design. Sometimes I need a low offset, or low bias, or sometimes that doesn't matter, and I need to operate up to 30 or 40V, and max supply is important.  Sometimes I need both. Sometimes I need high bandwidth, sometimes output drive is important, etc.

The other day, I was specifically looking for a DC opamp that was good up to 45V  and could drive a 40mA load.   That was my search criteria, and I just used the parametric tools on the manufacturers website to find some candidates. Then I drill deeper into the datasheet to make sure there is nothing to bite me, or that it fits all my other secondary requirements (is it unity stable, if I needed it, or what's the GBW? do I need to cascade another opamp because I am exceeding the GBW, will it's offset and bias harm me, if I care, etc)

Yes, there's a lot to consider when choosing an opamp, I don't even think Dave can cover it all in one video

[SeanB]

I had that with a piece of equipment that used OP07's there, i replaced them with 741's in a TO100 can and added a heatsink. Worked well, the original ones had overheated and had drifted badly, the new ones stayed cool. The application was only 12 bit, and the new opamps were perfectly happy there. At the time if I had to order the OP07's this would have taken 2 months, the 741's were in stock, and I had plenty that had been tested and had JAN-TX certificates.

[c4757p]

feedback loop stability? its not really as fundamental, but a topic not many of us understand, and very important in most circuits...

e.g. pole and zero compensation, bandwidth limiting, etc,.

+1   

+20 

[Neilm]

One thing that might be good Dave touched on in a recent episode. When tearing down the Uni-T UT513 he mentioned the Guard terminal. Now I know what this is and why I would want to use it but there are a LOT of people out there who don't - event ones using Insulation Testers at work.

Neil

[bullet308]

Not sure if it quite qualifies as a "fundamental", but I for one would like to see Dave take his DC voltage doubler to the next level and talk about high voltage, low current applications.  Up to 2kV in the microamp or low milliamp ranges. But that’s just me. 

[Alana]

Simple transformer based linear power supply. Sounds simple but i learned the hard way that this is tricky stuff with [as Dave says it] lots of traps for young players.

[marvkaye]

Maybe not a great topic to detail on a whiteboard, but I'd sure like to see a presentation on external triggers... scopes & multimeters & other test gear have inputs for them but when and how and why do you use them? Advantages, disadvantages, traps, limitations, best practices, etc, etc...

[c4757p]

Maybe not a great topic to detail on a whiteboard, but I'd sure like to see a presentation on external triggers... scopes & multimeters & other test gear have inputs for them but when and how and why do you use them? Advantages, disadvantages, traps, limitations, best practices, etc, etc...

I second this. The trigger is the most versatile and useful part of the scope. You could spend hours talking about how to use it properly, especially on modern digital oscilloscopes. (And don't forget the analog ones! Lots of tricks there that aren't needed on digital.) External is just part of that.

[DarkPrince]

I had a thought earlier of a discussion I (and probably others) could benefit from. A clear explanation of Q factor and its influence on circuits (especially tank circuits). For some strange reason I don't believe our university has a course which covers the topic (or a section of my memory is completely missing). I came to the realization of a lack of understanding when I was reading an article someone wrote about a home developed LCR meter and how the Q factor affects the devices measurements. Baffled why this wasn't covered in the uni. Just chucking the idea out there.

[cthree]

uC clocking, crystals, load capacitors and such would be an awesome tutorial.

[azi]

I would like to see Dave do a video about why anyone ever needs 5 or 6 digit accuracy for a multimeter.

For what I'm doing now, 0.1% accuracy is perfect. I get more than enough accuracy without being distracted by extra information. As you can guess, I am not a gear freak.

It's easy for technical people to be fascinated by a long string of correct digits, but in practice, what are they really good for?

The only thing I can think of is when designing ADC or DAC circuits, and I may need to do that someday. But what else?

[c4757p]

How about one on the difference between accuracy and precision, azi?

One quick example: I recently built an electronic load that uses a quite small sense resistor (0.01 ohm). At the specified 1mA resolution, that's 10uV steps on the sense resistor. I was definitely exercising the last digit of my 5.5-digit 3468A while testing and characterizing the current sense amplifier. I'd have loved another digit or two...

I'm sure I could have found another way to do it. For instance, I could make it the lower resistor in a voltage divider, and then I could compute the voltage across it instead of measuring. But when a project is already complex, my will to complete it is inversely proportional to how much of a pain in the ass the little things like that are...

[alm]

Dave did a video about precision and accuracy a long time ago. It's not like the meaning of those terms has changed in the mean time.

[Smithy]

I mentioned this in another thread but Id still like to see one on inrush current.