RC Low-Pass Filter Deep-Dive - Phil's Lab

Passive RC low-pass filter basics, theory, real-world tests and demos, practical considerations, and examples both in the time- and frequency-domain. PCBs by PCBWay www.pcbway.com
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[TIMESTAMPS]
00:00 Intro
01:12 Altium
01:52 PCBWay
02:19 Basics
07:00 Time-Domain Analysis
11:48 Test Set-Up
12:14 Time-Domain Demo
14:41 Frequency-Domain Analysis
16:56 Bode Plots
19:53 Frequency-Domain Demo
22:29 Source & Load Effects
25:41 Loading Demo
26:59 Cascading Stages
27:53 Component Non-Idealities
32:08 Non-Idealities Demo
34:21 Further Practical Considerations
39:53 Practical Examples
45:29 Outro

[@PhilsLab]

Clarification on noise (ideal case): the only noise generator is effectively the resistor, however, the RC filter band-limits the signal. Thus, in the Johnson noise equation, plugging in cut-off frequencies, working out the maths.. we arrive that the output noise is v=sqrt(kT/C) (independent of R, independent of bandwidth). However, for a fixed/given cut-off frequency, we would like to decrease R (as stated in the video), as this will in turn increase C and thus decrease the noise. I'd suggest checking this out with a simple noise simulation in LTSpice. I should have explained this better in the video.

[@user-ww2lc1yo9c]

Have you seen EEVBlog's videos on Jellybean components? What do you think about them? Dave has not made any video on Jellybean SMPS yet. It would be great if you make this video instead :) We can always check out the Art of Electronics of course.

[@TheAMFT]

I had an idea to build an esc with a ST Microelectronics STSPIN32F0 with GaN mosfets to shrink the footprint and power use of a BLDC motor controller. Do you think this is feasible for a small power efficient alternative?

[@PhilsLab]

@@user-ww2lc1yo9c I saw that video quite some time ago, will need to rewatch it - but from what I can remember it's very useful. That would be a good idea for a video though (or something along the lines of 'my go-to SMD parts') - thanks for the suggestion!

[@PhilsLab]

@@TheAMFT I hadn't heard of the STSPIN* before - thank you for sharing, that looks very cool. I'm definitely going to look into that - will have to experiment a bit myself :)

[@user-ww2lc1yo9c]

@@PhilsLab The Art of Electronics can always be used for guidance, the last edition was in 2015 and its part 2 (extra stuff) was issued in 2020.

[@zeKite]

I really like this kind of videos where someone explains "basic" or some more advanced electronics stuff in such a good way

[@PhilsLab]

Thank you!

[@mohammadhushki96]

The amount of information on this channel is just so great and unmatched,, I'm really happy that I purchased one of your courses, not only for the great amount of info and details, but also I want you to keep doing this kind of videos on KZbin. Thanks Phil 🙏

[@PhilsLab]

Thank you, Mohammad - and thank you for your support, I hope you like the course!

[@szymon4602]

There are so many content on this channel. I am proud to be a patreon 😀

[@PhilsLab]

Thank you very much for your support, Szymon!

[@user-ww2lc1yo9c]

@@PhilsLab Have you made a video that covers the topic of data converters, more specifically choosing an ADC and creating the circuit to interface source to it i.e buffer amplifier and anti-aliasing filter; and choosing a DAC and creating the circuit to interface with its output i.e analogue reconstruction filter or low pass filter; and finally, the method to do PCB layout with these things?

[@thilinamedia6910]

Huge Thanks to all Patreons, Altium and PCB Way for supporting him..

[@nickalexander2505]

I really do hope you realize just how insanely valuable your information and page is. This is what the internet was made for, and I’m just beyond grateful I get to experience this sharing of knowledge in real time. Please keep the videos coming Phil, you’re the reason I’m pushing through electrical engineering

[@PhilsLab]

Thank you very much for your kind comment - many more videos to come! :)

[@DGNG-dd3to]

This presentation was amazing! Keep it up!!!!!!!

[@dancollins1012]

Wow, haven't even watched this video yet, but intro looks to be exactly what I've been asking for - thanks so much!

[@PhilsLab]

Thank you very much, Dan!

[@Jaygo41]

Great channel. Thanks for all your work, a ton of valuable info is made free and accessible

[@PhilsLab]

Thank you, Reid - you're very welcome!

[@AlejandroGarcia-rk5lc]

What an incredible and complete lesson related to RC filters. I'm eager to see videos like this, where it's supposed to know all that stuff but it helps a lot to those who are leain the beginning.

[@PhilsLab]

Thank you, Alejandro - I'm glad to hear that!

[@anexoworkshop]

What a masterclass! Congrats and kudos from Brazil!

[@PhilsLab]

Thank you very much!

[@fredflickinger643]

No questions, so very good!

[@PhilsLab]

Thank you!

[@pantelisEVs]

Great video once again Phil! Hope you are doing great. Cheers!!

[@PhilsLab]

Thank you very much - I hope all is well with you too!

[@augustinwaga4948]

Very interesting video, Thanks again Philip

[@PhilsLab]

Thank you, Augustin!

[@MegaTraxxas]

Such a deep dive into theory, I moved back in time to my university lessons about circuit theory😀

[@megoboss]

Thank you very much for this amazing video really !!

[@sandman94]

Great work. Very thorough 👍

[@PhilsLab]

Thank you!

[@fikretyldrm1100]

That is great video as a lesson . This is great channel

[@jakubvanek5723]

Yet again a perfect video Phil!

[@PhilsLab]

Thank you very much, Jakub!

[@TheEmbeddedHobbyist]

I used to calculate the component values, but then fine tune on the prototype stage. Other stages never seem to have the impedance I've calculated due to tolerances. Reminds me of when i had to calculate worse case max an min circuit operation to show that with the components tolerances the circuit board will always be within specification in production. Bloody hard work when you were doing it with a calculator 😢😢

[@BassheadMusicConnoisseur]

Most sane German electrical engineer on KZbin

[@matheokoning4456]

Another great video! Can I also use this for a ledstrip pwm dimmer that makes audible noise at 1khz?

[@leeslevin7602]

Brilliant, thank you :)

[@PhilsLab]

Thanks a lot!

[@sentient1640]

thanks

[@Mrpeacemaker2]

Excellent . Can you compare results with your Real-Time Software Implementation of Analog Filters? That would be interesting.

[@PhilsLab]

Great idea!

[@smartups1]

Next LC low pass filter .

[@gregreynolds5686]

Great stuff, thanks for the effort. What package do you use to do the circuit drawings in the slides? Tikz?

[@PhilsLab]

Thanks, Greg! I use draw.io with Latex typesetting - to me much quicker than Tikz for figures.

[@kamelk8027]

Amazing video, can you make the same video for active filters, and also some tutorials about "La place transform" to be able to analyse circuits.

[@PhilsLab]

Thank you! Yes, definitely plan on covering those topics!

[@enotdetcelfer]

Looking forward to a similar analysis on high-pass and/or band-pass tank circuits and variations. I understand it theoretically, but not from this kind of tinkering pov.

[@PhilsLab]

That's to come!

[@bencemarta5222]

Recently I had related problems with a flyback topology power supply. There were only electrolytic capacitors in its output filter and comething caused stochaicly occuring sinusoidal high amplitude RF noise (40-100MHz depending on the powered device) on the output (like +-8V). I think it was some LC ringing but didn't trace it back to the exact source. The solution I had was to disassemble the power supply and add 100pF + 100nF capacitors wit appropriate impedance characteristics to the output filter and the noise is instantly down to about 130kHz and +-2V at worst. So knowing this I'm adding some serious RF filtering to the final version of that device.

[@PhilsLab]

That's interesting, thanks for sharing! I'm actually currently working on a design which incorporates an isolated flyback topology converter. Will see how that pans out!

[@jeffreydijkstra3391]

Hi Phil, I would like to buy your course(s) , however I use Fusion360 to design PCB's as a brand new embedded hardware engineer. Would the course be useful? or would you advice otherwise because you are using Kicad. Best regards, Jeffrey

[@PhilsLab]

Hi Jeffrey, both courses will be helpful regardless of what software you use. However, the mixed-signal course is definitely quite tailored towards KiCad. The advanced hardware course is far more tool-agnostic.

[@MatiasJHZ]

The total output noise is only dependant on the capacitance. Bandwidth is 1/(2piRC) and both Rs cancel out. So increasing R would not really increase the noise.

[@PhilsLab]

That's true that the Rs cancel out and it's only dependent on C, for the LPF case. However, for a given/fixed cut-off frequency, if we increase R we need to decrease C, which thus increases the voltage noise. Therefore, it makes sense to choose a smaller R to give a larger C, in turn giving lower noise. You're right that it's an 'indirect' cause though and I should have explained it better.

[@MatiasJHZ]

@@PhilsLab ooh ok! It wasn't clear that it was under the constraint of a given bandwidth. Thank you

[@christopherdev3359]

Can you do a video on how to properly route DDR4 and what the Layout differences compared to DDR3 are?

[@PhilsLab]

Yes, that'll be a part of the Zynq Ultrascale+ design.

[@tamaseduard5145]

👍🙏❤

[@massinissaautoscan]

dear sir please how to get quasi sine wave (inductive crankshaft signal for automobile -12V to 12V ) from square wave i.e crankshaft signal (hall effect) varing from 0 to +5 VOLT using for exemple a low pass filter note: the frequency range is : 500 HZ TO 30KHZ THANKS SIR

[@weeeeehhhhh]

Am i going crazy, or was there a crosstalk video posted and removed last week?

[@PhilsLab]

Yeah, there was but there was an error in it. I'm also gonna add in a real-world demo, then re-post.

[@weeeeehhhhh]

@@PhilsLab brilliant, I was tackling that exact problem in work this week. Please keep up the fantastic work.

[@user-ww2lc1yo9c]

@@PhilsLab I am confused about something. Do we use PCB tracks to connect power or use copper pour planes? If we use planes, we still end up using vias anyway to connect to the IC on the top or bottom layer and where do we put the decoupling capacitors? Have you made a video on these things so far?

[@bernard.tomasevic]

Why’s crosstalk video missing?

[@shamssalehin2376]

Please share slides...

[@farouktilaoui7489]

Hi Phil, could you do the same video for common Mode filter

[@PhilsLab]

Thanks, Farouk - next will probably be ferrite beads.

[@farouktilaoui7489]

@PhilsLab you are a great person I learned a lot from you and your courses

[@PhilsLab]

Thank you, I'm glad to hear that!

[@riyazkureshi8113]

I am also waiting for the same. much informative 👌

[@dance_536]

Drone receiver 😢🙏🙏🙏🙏🙏😭😭😭😭🙏🙏🙏🙏🙏🙏🙏🙏