Square Wave Ringing / Overshoot & High Speed Buffer Amplifiers & Scope Leads

Hi,
A Look at Square Wave Ringing / Overshoot & High Speed Buffer Amplifiers

[@Sam-yz7vm]

Great tip, thanks John

[@JohnB-2021]

Thank you Sam, happy new year.😁

[@brokenicry]

wow... thank you. YOu have no idea how many of my questions this has answered.

[@JohnB-2021]

Thank you for taking the time to comment :) I'm pleased the video helped.

[@kieranj67]

Hi John, thank you, an excellent video on a real world problem with scoping high speed clocks. I was experimenting with the silicon labs SI5351 a few weeks ago, and ran into a similar problem with overshoots and distorted waveforms. Luckily I had a few scope probes to experiment with, actually 3 with the same spec but one gave a clean representation of the waveform I expected. The other two after watching your video probably had defective ground clip connections or else I fried them when using them for measuring kick back spikes on 230V solenoids. You should market your spring contact thingies, they worked beautifully, Kieran

[@JohnB-2021]

Hi Kieran, Thank you very much for your comments, I'm pleased the video helped. After doing this video, I found one of the short earth connectors in the scope box lol I hadn't noticed it when I bought the scope years ago. I'm doing a video very soon on 'Snubber' networks, it sounds like you need one on your solenoid Thank you

[@_Junkers]

Are you able to explain how the additional impedance of the original earth lead created the ringing?

[@JohnB-2021]

well, in short, It's due to the inductance of the earth lead and the fast high speed switching. The inductance acts like a coil, absorbing electrical energy and releasing it. I say inductance because it's the primary cause. Impedance is inductance, capacitance and resistance. I guess I could add capacitance to the equation. There is a whole field in electronics on inductance, and the formulas get complicated / too complicated for me. I'm guessing you know most of it since you used the term 'impedance'?

[@_Junkers]

I have a rough idea, I understand the fundamental elements. I know ringing like that is often attributed to the Gibbs phenomenon, but don't understand it at depth.

[@JohnB-2021]

All I know about inductors / long bits of wire causing inductance is - As the frequency increases (faster on and off times) the inductance becomes more significant. Switch the power on, a magnetic field will build up around the inductor. As the power is switched off, the magnetic field will collapse and induce a voltage into the inductor. That induced voltage will obviously affect the original voltage, it also apposes the incoming voltage. That induced voltage will cause a current to flow which will cause a magnetic field again, but not as strong. Together with capacitance, the weaker magnetic field will induce a smaller voltage giving a smaller current giving a smaller magnetic field, and it continues until the energy is gone. It's called ringing. And that is only with the first switch on / off. Look back on cars with points and a condenser (capacitor) The condenser together with the coil was a 'tuned circuit' It was there to cause 'ringing' to give us a longer spark.

[@Ghostpalace]

Have you tried using an active probe?

[@JohnB-2021]

Not at Keysight prices

[@yosoy1loco]

Dear John B, i stumbled upon you channel by accident. For weeks im now grinding through articles and videos concerning LoadLineCalibration of VRMs on motherboards, which should explain what vdroop is. Im no electrical engineer, but obviously some kind of autist, since i cant sleep anymore, cause i dont understand all those explanations. I have really read so much and there is something in all of the explanations that is wrong and that makes no sense, yet i cannot nail it down. It makes me crazy. If you wonder about some examples, take this article: en.wikichip.org/wiki/load-line_calibration So now i broke down the problem in my head to the the cause of the ringing/aka overshoots, which i situate in the VRMs reaction to voltage changes by increasing the dutycycle. Longer duty cycle means more time for "loading the spools/coils" to generate a higher "net voltage", but also increases the ripple. The ringing in that aspect is the direct result of "several" changes to the switches of the buckconverter within a very small timeframe until you find the exact period needed to match the desired voltage. If this explanation i came up with myself is correct, then a lot of articles and explanations on this famous topic in the PC-community are quite misleading, even wrong, as they do not differentiate the compensation of natural voltage drops and intentional vdroops. Yet, im not sure that im right. Im just sure, that they are also not right. Have you an idea of what i say could be true or a suggestion if the article is correct or another advice for reading to understand what causes ringing in that aspect (load line, voltage drops on a pc system) ?