Electronics tutorial - Separating Common Mode and Differential Mode signals

#69 In this video I look at how you can generate both Common Mode and Differential Mode noise both in the LTspice simulator and in real life - see how a generic model for this looks like but also how a real life implementation can be done.
And then I look at the basic principles of how to separate the 2 signals again.
More on the topic:
Common Mode Choke: • Understanding the Comm...
Passive CM-DM separator: • EMC tutorials - Passiv...
Some external documents that go more into the technical details:
publik.tuwien.ac.at/files/Pub...
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[@iamswastik]

I don't know why your subscriber number is still stuck at 18K. You deserve way more subscriber. Excellent video. Thank you!

[@wueric4076]

Good to see you demonstrating Math menu functions of oscilloscope. I remember the old HP3577A Network analyzer have DEFINE MATH functions for multi-receivers in frequency domain although it's not spectrum analyzer.

[@pietmatsobane6790]

Thank you Sir!... Running the experiment in real physical oscilloscope made things even more interesting 🕺🕺🕺

[@FesZElectronics]

I was really surprised just how well it turned out in real life; I was afraid that the simulation would be just too ideal in comparison with the practical circuit.

[@DiegoColl44]

Your videos are very great, I already shared your channel with all my colleagues. keep creating quality content. Thank you. Saludos desde Argentina..!!

[@FesZElectronics]

Much appreciated! Thank you!

[@arthurm7846]

This channel is a gem, great video! Thanks a lot!

[@sidravi3885]

your videos are simply amazing.... I have learnt so much from you .....can you make a video on how common mode noise is generated in typical high frequency electronic circuits?

[@rogeradi]

I love to learn from you. Very informative.

[@sarperarslan3085]

Mr. Thank you for that great explanations

[@dominikworkshop6007]

Very informative video!

[@FesZElectronics]

Glad it was helpful!

[@brankelly1921]

Great video, thank you so much!

[@FesZElectronics]

Glad you enjoyed it! Thank you!

[@thunderbolt55]

Amazing, thank you for this video. simple and precise. Interested watch your video measuring it on a spectrum analyzer

[@FesZElectronics]

More than a year later, I actually got to do that :D kzbin.info/www/bejne/nJmzhaGlg7Z6laM

[@ihtsarl9115]

Thank you for posting this video it would have been nice to show how to filter out these noises

[@khalidchigane3540]

first of all, thank you for your video it's very helpful, I just have a question about the source of the common-mode voltage as we know we apply just the differential voltage between the two wires but the common one exist too

[@97mesut]

thanks so much

[@akashtanwar1939]

This is good stuff.

[@FesZElectronics]

Thank you! I'm happy you are enjoying it!

[@sridharchitta7321]

Differential-mode and common-mode signals are important to understand in the design of complex signal-conditioning circuits which use operational amplifiers in medical diagnostic, industrial control and military applications. Operational amplifiers mainly excel in performance to provide a high common-mode rejection ratio and high gain. By using negative feedback, its overall gain, input impedance and bandwidth are determined by external components without these parameters being affected by the op-amp’s parameter variations due to external influences like temperature and so on. Most amplifiers built using discrete transistors will not be able to match the performance characteristics of an operational amplifier like CMRR, low drift, high input impedance and stability of gain. Engineers are so used to thinking and visualising currents as differential-mode in circuit analysis that they find it hard to switch their thinking to common-mode currents and their effects in say, amplifying circuits. It will be instructive to understand and visualise Current at its most fundamental level in the presence of electric fields in ordinary conductors. Electrostatics and circuits belong to one science not two. To learn the operation of circuits, Current and the conduction process, resistors and how discussing these topics makes it easier to understand the operation of capacitors, inductors, diodes and their operation in amplifier circuits and circuit theory watch these two videos i. kzbin.info/www/bejne/ioXXpWVul5aXj9E and ii. kzbin.info/www/bejne/bnO0fpKurJeFnNE Most common-mode signals originate because of sources external to the system, and the energy in them circulates annoyingly until it is dissipated in resistive portions. They can be generated internally if proper cables are not used for coupling signals at the frequencies of the signals they carry. Therefore the need arises for amplifiers to amplify only the useful differential signal and reject the common-mode component which does not belong to the signal conditioning system. Such an amplifier is used as the first stage of an operational amplifier which opens the door to allow a signal from a sensor ‘in’, so to say and so the importance given to this stage. Topics related to these aspects are discussed in chapters 3 and 5 of textbook 4 (see last frame References in video #1) and a power point presentation with animations “Basic Action of a Differential Amplifer-Heart of the Opamp” which explains differential amplifier with a U-tube manometer analogy of differential- and common- mode signals is included in the CD alongwith this book.

[@Bazz1TV]

in an unbalanced system, is it enough to connect oscilloscope channel A to circuit signal, channel B to circuit ground, with scope grounds floating, creating a floating differential pair to perform MATH functions on to learn CM and DM properties? I am looking for a budget friendly way to measure improvements in CM noise when applying filters, with the major tools available being oscilloscope and function generator.

[@gianlucabartolocci1613]

good morning your videos are wonderful, do you happen to have one that measures the thd of an amplifier between the input and output Vsin signal) the classic settings I'm using don't work or in any case I find anomalies. grazie

[@jonnymakers9560]

differential noise and differential signals are different. Correct? It seems like common mode and differential mode usage depends on what we are talking about, noise, signal, rejection ratio etc. which makes it confusing

[@robertthurman8412]

Hell FesZ, So, in the real world if you have a class I device or a class II device you would make these measurements with respect to chassis i.e. you would use two probes with each of their grounds connected to chassis? The two signals (sig1 and sig2) are representing the signal and return path correct?

[@campbellsmith9849]

Why doesn't the DM noise also double when it is isolated? By subtracting the two lines, I'd expect something like 5-(-5)=10, or -5-5=-10.

[@FesZElectronics]

In the case of the CM noise, I was measuring the noise in reference 2 ground both times, so the values added up; with the DM, if its properly floating then the values in reference to GND would be half of the initial signal; both lines are oscillating in reference to GND, when one is increasing the other is decreasing and the total peak to peak never exceeds the initial input value - rather than having 5-(-5) the total would be 2.5-(-2.5)

[@vigneshsiva1580]

how to view the addition and subtraction of two channels on spectrum analyzer

[@FesZElectronics]

You can do that only if first you use a passive or active circuit that processes the 2 signals. There are some commercial products that can achieve this.

[@andpe161]

Very good, but you stopped just before the most useful part!

[@FesZElectronics]

In the mean time, part 2 did come out - kzbin.info/www/bejne/nJmzhaGlg7Z6laM

[@andpe161]

@@FesZElectronics Perfect, thanks! I did search but with the wrong search term.

[@j3s0n]

Dutch?

[@FesZElectronics]

No, Romanian