Negative resistance and the Negative Impedance Converter
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- čas přidán 14. 01. 2018
- What does chaos theory, load cancellation, and op amps all have in common? This video discusses negative resistance, provides an introduction to negative impedance converters, and demonstrates some of the interesting circuits that use it.
References and a derivation of the negative impedance converter circuit's input resistance: www.analogzoo.com/2018/01/nega... - Věda a technologie
Please don't stop making videos. This is a great explanation!
Another application of negative resistors I've seen is increasing the Q of spiral inductors fabricated with the metal layers on silicon chips. Typical spiral inductors have a lousy Q factor that makes them almost useless for RF filtering (Q=1.5). When you cancel out the inductor's resistance with a negative resistor circuit, you can increase the filter Q factor to give much better preselect filtering. Using a good preselect filter in front of the LNA really helps you pull in weak signals.
Exceptional explanation. I have to do an experiment for Uni on this and I couldn't make heads or tails from the lecturers explanation. THANK GOD for angels like you that take their time to share their knowledge- You are officially a SUPERHERO
Nice to see the video from you after a long time. Your videos are great. :)
Thanks! I'm trying to get back into making them again this year, after a long hiatus. :)
Agreed
Your videos are always well put together and thought provoking. Also you just always happen to cover topics that are some of the most interesting ones in analog electronics. Glad to see you're back to making videos!
Thanks for getting back to youtube! You're doing really good job in explaining complicated things simple enough for understanding and still not over-simplified.
Thank you, I was trying to figure out how this negative resistance op amp stuff works after reading about Chua's diode. This is exactly what I needed. Saves me a lot of time figuring.
Dude! Keep making videos. Where have you been. Nice to have you back. This was amazing. Thank you
Always learn something from your videos, thanks
Ur all clips are superb. Not only helpful to who learn this subject, but to those who teach this subject.
Awesome job, I graduated with a BSEE in '92 and this video hurt my brain (in a good way ;o) Keep up the good work and thanks for sharing.
Thanks for another great video. Yours are some of the most interesting EE videos out there.
Hope you haven't given up on making videos; would sure like to see more. Thank You!
I was attracted by the oscilloscope screen. Perfect explanation. Thank you.
P.S. I hope you will post more videos in future. You channel is one of the best on CZcams about electronics.
The world's best teacher thanks sir
Brilliant presentation of the concept. It’s like being in school again, but better!
I’ll have to build up an oscillator like the one shown here as an oscilloscope screen saver.
Thanks for another great video.
Hi devttys0, hope you are still active on this channel. I really appreciate you shared easily understandable material for beginners and more advanced electronics enthusiasts. I really like to know who did you learn from? your teacher much have been really awesome.
I built a couple of "negistor" oscillators that gave a pretty good saw wave. Love this topic : ) Thank you!
Hi. I've recently found your excellent channel here, and want to encourage you to make more videos. The "Jim Williams, Test your Analogue Design Skills" ones are particularly interesting. Do you post anywhere else these days?
Thanks,
Alan
I think I accidentally made a chaotic circuit today. Your video helped me understand a lot of things today! Cheers. I had made a proper one with an ad633 before but it was just a bunch of wires to me
Thanks for a great video!
Great explanation! I would love to see something about tunnel diodes!
You should check out Alan's (+w2aew) channel, he's already done a great video on tunnel diodes here: czcams.com/video/PuG8CCUbg58/video.html
Like always, very vert interesting
very nice video
NOW THAT WAS INTERESTING!
Great video! Loved the very cool "Strange Attractors" demo at the end. My scope doesn't have X-Y mode, :(
This is so cool! 😊
Excellent!
Nice and interesting vid...!!
Where did this guy go? Come back!
put a speacker on the output so I can hear "the caos"
Clever :D
@@alperenalperen2458 This is a very good idea! Have you tried it yet?
You know the best thing that came automatically to my head as negative resistance is a photovoltaic cell, could probably make a nice example ;-)
for first time when i heard "negative resistance" i imagined a something like a photodiode
Great videos bro, why you don't continue doing videos?
cool stuff, thnx for sharing. Even though you haven't made vids in a while I still sub'd. =Encouragement = Yes you have an audience
What happened? Why did you stop making these wonderful videos? I wish everything is alright.
what direction are the electrons flowing through the circuit when the meter goes from 1 to -1?
I didn't know any of this. Very nice explanation and demonstration. Thank you! One thing, though... in the amplificator circuit I guess there would be some propagation delay in the negative resistance OpAmp. How would that affect the circuit? Would it tend to oscillate? Should the second OpAmp be e.g. twice as fast as the first one? What kind of freq. compensation network/filtering should be used?
As with any circuit using an op amp, you would need to select one that has sufficient gain and slew rate for your application (www.radio-electronics.com/info/circuits/opamp_basics/operational-amplifier-slew-rate.php). There will always be some propagation delay through any circuit, and there is no general requirement for the second op amp to be twice as fast as the first; it really depends on the application.
The biggest concern with oscillation is that the negative-resistance op amp is employing positive feedback through the resistor connected from its output to it's non-inverting input. If driven from a low-impedance source (such as another op amp), that low-impedance source has greater control over the voltage at the non-inverting input and will tend to suppress oscillations.
I like how he's using a screwdriver to point at things on the board :)
Negative resistance for any AC component is a power generator.
LMD analog circuit has achieved negative resistance by phase shifting voltage and amperage by 180 degree. Thus, you get an increase in power. Passive component such as inductor and capacitor are not passive at all.
Inductor produce power first then absorbs power from the circuit. Hence the name, "Reactor".
Capacitor stores power before releasing it back to the circuit. Hence the name, "Condensor".
Eric P. Dollard is a clever person I must say to create this circuit. All credits goes to Tesla as this circuit is an analog version of Tesla Coil.
Due to mutual inductance, voltage drop across multiple inductors in mutual inductance in series are reduced. Thus, more "current" flows into them, forced to generate the missing magnetic flux. Yet the reactive flux cancels it. The process continues until maximum of source "current" can flows into them.
However the "current" flow is limited by the first inductor with reduced emf. Therefore it needs a secondary "current" source. Capacitor produced displacement "current" which can be used to supply the inductors. However due to insufficient voltage, the capacitors doesn't generate that much. Therefore maximum amount of capacitors' amperage are supplied to the inductors. Thus creating heat due to capacitors behaving badly.
This is the simple LC transmission line.
Now try 1/LC transmission line. You get Tesla transmission line.
That is all I will say for now. Tesla transmission line is LMD analog circuit. Capacitors in series, inductors in parallel. Check the schematic.
Its good to see another student of Dollard and Tesla that understands these things. I have studied Dollard's work for a looong time now. I even bought a box of his research material from boarderlands science. Has one of his high voltage electricity wood carvings in it. I have studied a lot about magnetics and induction effects. I got to meet him too at the Idaho conference that Murakami runs. First time he came out of the desert. I would love to discuss more about this. I just saw this video and was thinking how can this apply to John Bedini and bucking coil action. Really glad I read the comments here. Lets talk! I build high voltage electrical test equipment at my job. Including EMP pulsers based on compact flat spiral strap tesla coils.
johncappelletti1@gmail.com
hope to hear from you soon. I don't have anyone to talk to that understands this stuff.
hey! any way you can help with negative resistance on a collpits oscillator/ with transistors?
thanks
If I have a NIC whit the tree resistance of the same value and a input voltage of 9v, it is possibly that i get Vo= 18v?
Cause i put it into a simulator and gave me Vo=6v
I got around 5V at the non-inverting terminal of op-amp.No oscillations at all.The voltages across the two capacitors are fixed at 0V and 5V.My supply voltage to op-amp is +-12V.Op-amp is TL084.What am i doing wrong?
Can I have a voltage source with consistent negative output impedance with different load?
Nice scope
actually at first i thought it was BS,but i watched it and understood good video
Old time radio,s work on negative resistance "miracle" Regen receivers, TRF receivers... RF stages input impadance is a with negative resistance component... Negative resistance reduce loses in LC tank, antenna and enviroment around antenna ( tought antenna,s capacitance )... For radiowaves this receiver is a real "black hole" and can get DX reception.
First off, great video, really love the intuitive lead into the negative resistance circuit :D
If you put a resistor of 1k in series with this -1k resistor, could it work, that should make a 0ohm resistor, but analyzing the op amp circuit, it would only be stable for an input and ouput of 0v. But if you were to put a larger resistor, like a 2k in series with the -1k, it should make a 1k resistor, but that doesn't happen, the op amp becomes unstable, but becomes stable when you reverse the inverting and non inverting input. Is this a thing? Is there a way to make it work both ways? Sorry about the long question, it's just something interesting that i found while tinkering.
You do have to be careful about oscillation with this circuit; after all, you're providing positive feedback to the op amp's positive input! Hence my second example of using one as the active component of an oscillator. :)
When driving the op amp from a "stiff" voltage source (i.e., a voltage source with low output resistance), that voltage source helps to hold the op amp's input at a steady voltage which generally prevents oscillations. When you add series resistance to that voltage source (such as your 1k or 2k resistors), it is easy for noise voltage to build up at the input terminal of the op amp, which the op amp will then dutifully amplify and feed back to its own input, ad nauseam.
hope you can update.
I have a question regarding the first circuit with the negative resistance stage added to the output of the LTC1050. Does this improve output impedance while maintaining the accuracy and drift properties of the LTC1050? Or does the "negative resistance" circuit introduce issues? I am curious if this circuit would be useful in buffering output stages of say reference voltage standards.
The accuracy of the LTC1050 is still maintained; there's a good Maxim app note on exactly this application: www.maximintegrated.com/en/app-notes/index.mvp/id/1868.
The main down-side to this configuration is the NIC op-amp has to output 2x the voltage; so if you wanted to drive your load with a 5v signal, the NIC op-amp would need at least a 10v supply (assuming a rail-to-rail op amp). Depending on your application, this may or may not be an issue.
What are the cons and pros of using a buffer after precision opamp and getting the feedback of precision opamp from the output of buffer compare to this method?
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This circuit won't be limited to a load.
I need more videos.... Where is this guy's Patreon?
I always visualize DC voltage using a water analogy.. Voltage would be how high the water is above ground, and resistance would be the diameter of the pipes, capacitance like tanks, and so on...
It's an unusual power supply that can sink current!
Hello, I'm a #11001 subscriber)
Nice👍
How much did you have to fiddle around to get the oscillator to actually oscillate? I remember it only oscillating when I turn my back to it....
With the values shown on the white board in the video, a cheap single-turn pot wasn't too touchy and worked well. I was using a TL081 running from a +-10V supply in the video. Running from lower supply voltages makes it harder to tweak the resistor into oscillation; replacing the silicon diodes with diodes that have a lower voltage drop (such as schottky diodes) helps there, and with a rail-to-rail op-amp I've had no trouble running the circuit from +-2.5v. I haven't played around with the inductor much, but the general consensus is that it needs to have relatively low internal resistance; op-amps can be used in place of the inductor, but I used this inductor from Digikey: www.digikey.com/product-detail/en/bourns-inc/RLB1314-153KL/RLB1314-153KL-ND/2561390
Shouldn’t the difference between input and output be closer than 30 microvolts on the LCT1050? I think the max input offset is like 4 microvolts on it. Must be other factors at play but I’m not sure what
I suppose it could be thermoelectric junction something or another
Neat
ohhh .. classic strange attractor pattern on the scope
Thanks, I get it! Sort of like j, square root of -1, to wrap my head around. Chaos, true randomness from this Chua circuit, yes?
Chaotic systems are not considered truly random. The Chua circuit, for example, is governed by a set of differential equations, and is thus deterministic. If you know exactly what input values you started with, you can predict the output at any given time. However, one of the foundations of chaotic systems is that they are very sensitive to initial conditions; changing the input values even very slightly causes the output to be predictable for a short period of time, but it will rapidly diverge from the predicted results. Since no tool or computer has infinite precision, one can never know the exact input values, and thus chaotic systems are not predictable in the long-term (real world example: weather forecasts are usually pretty good for the next few days, but they can't predict the weather for the next few months). So, yes, the Chua circuit can be (and has been) used to generate unpredictable random bits, but it's still not considered a source of "true" randomness. It's pretty damn random though. ;)
devttys0 Got it. If you're inclined, I would be in interested in a video expounding upon TRNG sources/circuitry; from PRNGs to "random enough" to "True Random" for a particular use-case, e.g. crypto. In any event, I'm subscribed as your content looks pretty interesting in the "lost" art of analog electronics. Rick.
Are we talking about conventional or electron current flow?
Conventional
Let's hear some audio from the chaotic oscillator :)
It mostly sounds like a lot of noise :) czcams.com/video/MxU0AUXXyf0/video.html
Sounds like an old modem.
So, if I replace the resistor with a capacitor I would get a negative capacitance?
Yes, exactly! This circuit is more formally known as a negative impedance converter: en.wikipedia.org/wiki/Negative_impedance_converter
I hope you'll consider making a discussion of those (NICs) in your next or upcoming video - particularly w/r/t filters.
And gyrators too...
This is so cool, thank you!
9.52 Instead of cascade with neg. resistor op amp, why not change r 1k to r 1M in replace thats more easier.
Still alive??
I’m not sure I understand. I think you’ll have to come give me a personal lesson. 😏
Pamela Cukor Personal lectures are available upon request. I accept payment in the form of liquor, bacon, or old test gear. 😂
devttys0 oh, you KNOW I have bacon. I’ll cook you all the bacon you want! 😁
Still alive?
More or less ;) Work and personal life have been keeping me from projects and videos, but I'm hoping to have something up in the next few weeks.
Pardon, and with respect. While I appreciate the thought-effort put into this presentation, for me, I feel the term "negative resistance" is - at best - a sophistic re-labeling of an established electrical component. Consider electrical resistance and superconductivity (en.wikipedia.org/wiki/Superconductivity). If current science 'observes' zero resistance given extreme environmental conditions, it seems a "negative resistance" would be beyond today's technology to achieve. "Negative resistance" would thus appear an interesting conversation point, yet it begs for an alternate label. Thx.
I agree that a passive component exhibiting negative resistance wouldn't be possible, as passive components cannot generate power. However, there are active circuits (such as the one discussed here) and individual components (e.g., tunnel diodes) that exhibit the property of "negative resistance", and the term itself is well established in electronics.
Think of it this way: a normal resistor dissipates power (typically as heat). So a "negative resistor" must *supply* power (e.g., the op amp in the video). Of course, usually refer to this as a "power supply", which often makes more sense, but in certain contexts "negative resistance" makes circuit analysis easier (such as the concept of canceling out a load resistor, as shown in the video). Many oscillator circuits model the amplifier portion of the oscillator as a "negative resistance" as well.
Admittedly the term may seem confusing at first, but it's all about perspective. :)
"it's all about perspective", and some perspectives are especially convenient to adopt. Saves drawing 4 components in the MCP601 circuit. :) Admittedly, the term "negative resistance" is a little off-putting... it leaves a bit of a 9V battery taste in your mouth... for me anyways.
#DesignsPassiveNegativeResistor #PhysicistsReverseTheoryAboutTheInevitableHeatDeathOfTheUniverse
I heard hashtags were in these days...
Firstly any power generating component has negative resistance in operation, trivially, so negative resistance is a real thing, its no more abstract than positive resistance. Of course there's no such thing as a fixed-value
negative resistance, we tend to have (imperfect) voltage sources as common power generating devices like batteries. R = V/I, if the signs of V and I are different, the resistance is negative by definition. Resistance is just this ratio.
Secondly we should be careful to distinquish actual resistance (of a simple two-terminal device), effective resistance (between two nodes in a more complex circuit as here), and negative resistance slope, as in a tunnel diode, where the resistance is always positive, but the _slope_ of current against voltage is sometimes negative.
In electronics its commonplace to talk of the effective resistance as just a resistance, such as the output resistance/impedance of a feedback amplifier.
Note that once you have a negative resistance slope, its straightforward to turn that into an effective negative resistance by shifting the operating point until the negative slope part crosses the axis. And this is invariably the kind of thing you do in ac circuit analysis all the time, so for ac circuits there is no useful distinction between negative slope and negative resistance.
Why do I feel like a "flat-earther" who accidentally walked into a round-earth symposium? Ok, I do, I do, I do believe in negative resistance. Will this release me from house arrest?
Just to clarify, tunnel diodes exhibit negative differential resistance not "absolute" negative resistance.