EMC Filter Design Part 1: Understanding Common Mode and Differential Mode Noise

In this video Dr Ali Shirsavar explains the type of noise (common mode and differential mode) that we need to filter in order to pass the EMC test. For further information on Biricha's EMC filter design workshop please visit: www.biricha.com/emc

[@ramazanyaman2142]

Thank you Mr. Shirsavar for your explanation. It really helped me to understand the basics regarding Common mode and Differential mode currents in an easier way.

[@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. 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 smplifier 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.

[@hugohuaman1487]

Thank you Mr. Shirsavar for your explanation.

[@basaltnow]

as usual...brilliant explanation, just stellar.

[@StefanStern145]

Wow! Thank your very much! This is the best explanation!

[@agstechnicalsupport]

Good and instructive video. Thank you for posting !

[@diegobrumchaves5182]

You are a amazing teacher

[@bobbauvian7700]

thank you so much. but may I say, something while you are running those markers on the paper the noise make me feel like my limbs are coming off.

[@nishantkumar-jz7hb]

Hello Sir...I like the way you explain these topics with simplicity......I have a question: How to visualise the common mode noise..when the return is sorted with earth.... Also on the digital circuits of PCB...say a LVTTL clk singal....when normally the return is a DGND plane....how to visualise the common mode and differentiation mode current.... Please give your inputs...

[@joels7605]

Excellent explanation. Thanks.

[@travisjayday5757]

So much better than my prof, ty!

[@mohammedshalash7842]

Too advanced for me, I need to design a simple common mode to measure the differential leakage current (50 hz 230V AC) any advice will be very helpful and appreciated. THANKS

[@mumbaiverve2307]

Very , very nice Sir.

[@daweima7098]

Thanks for your video.

[@samamani5423]

thanks for the video .

[@kelma5504]

Since you drew the direction of -ve idm in the direction opposite to +ve idm already, the waveform of -ve ldm should have the same shape as +ve ldm, instead of being inverted.

[@korkutkutaymetin1581]

Thanks for the video series but there is only one thing that ı do not understand. I am designing my own emc filter for my ac-dc power supply. I do not know Fcutoff and L-C. Can you help me please. (By the way my power supply works on 47to63 hz is that my Fcutoff ?)

[@Mahesh-uy8jw]

Thank you

[@opticalmixing23]

Ty profeasor

[@ravdobrzynski]

0:32 +ve Idm = -veIdm ?? mirrored? Fliped? FIFO? FILO?

[@ahmedazad7704]

Dr. Ali, you are the best. I was looking for some simple explanations regarding this topic for soo long...please make more videos on the EMI/EMC issues

[@zhitailiu3876]

Every time, really excellent tutorial! Thank you so much!

[@seeker4430]

Holy god.... Something i was searching for so long... God bless... Keep up the good work... Thanks!

[@ahmetcemalkurtulmus6180]

Thanks for your valuable information

[@JOVIFLOCAS]

Thanks for the information good work

[@TanvirAhmed1990]

great explanation

[@tamyboy1]

You are a God sent

[@infcastro1]

Man! Great information but that market noise is painful to hear. Please please please do something about it.

[@James_Bowie]

What I think needs to be made clear here is that common mode currents flow in the same direction as each other and are additive, as compared to differential mode currents which flow in opposite direction to each other and are thus subtractive.

[@harrygarcia5822]

Good videos,but the marker noise is huge, please try to fix that somehow