Passive RC high pass filter tutorial!

[@samuelcampos441]

That moment where you are in college and you need to come to youtube in order to understand what your teacher couldn't get you to understand... Thank you!!!

[@MoooseBlood]

Dude always. Lol

[@berkdeger]

When I graduated from college there will be KZbin logo and tittle on my degree instead of my collage name :D :D

[@lillipearse5579]

Too true.

[@iamisro6636]

That moment when you turn random buttons to get desired output on CRO and when you get it , you have no idea which button you turned to get it . 😂😂

[@M6MDR]

Ironically, most of my college learning came from KZbin - however, one should realise that good research techniques are required when doing so. There's so much nonsense floating about, a good researcher must have the ability to distinguish the accurate and useful information from all the click bait, hype and other nonsense.

[@davidbazaga4924]

If my electronics professors explained like you, my following exam would be a piece of cake. Thank you soooo much :)

[@ArturMichajluk]

OMG. 11y and still one of the best tutorials. I have no clue why I stopped subscribieng this channel. Thanks man for your work!

[@darrencady4261]

That was explained perfectly. You said everything anyone needs to know and nothing they don't. Well done to a great teacher.

[@stever3886]

This is sooooo much GREAT information in this compact video. I love how you provide your motivation to make choices in circuit design. You could spend hours scouring for all of this information in different places. THANK YOU.

[@PantsLaRue]

This is wonderful! The break down of each part of the circuit and its purpose is so incredibly helpful. Thank you afroman! Plz don't stop.

[@meta_ai]

you taught me what 3 books failed to teach. thank you. at last some sense to the madness. every book just assumes a bunch of stuff that isn't clear at first. made me day. why dont you have more subscribers.

[@microdrone]

Love the Afrotechmods channel! I am glad this popped up, I once again got lost in the billions and zillions of other channels. This is a nice basic video, nice production quality and very well explained!! My trip back to the basics, I also adore the W2ae3w channel , you guys are both talented and entertaining!

[@TheCrazyStudent]

These videos are great!! The way everything is being explained makes it easy to understand. Please continue making these awesome videos.

[@saichaithrik7134]

One of the best explanations of all time

[@M6MDR]

Dude, your two videos on Passive High Pass and Low Pass filters explained the basics to me perfectly. For the past week I've been trying to get my head round the concept but all the information I came across was all Pseudo Babble and Techno Jargon, well above my head. This was perfectly explained and now I understand. I've even memorised the formula too! LOL. I'm working on a project at the moment which involves RF and Audio and I'm getting a distinct hum on the audio line from some sort of RF interference which I'm working to track down and eliminate. If I can't find it to eliminate it at source, I am going to cheat and filter it out of the audio line using a high pass filter with a cut off of about 250Hz so it's a gradual decline around the problematic frequency range. Thanks again!

[@Afrotechmods]

You are welcome. Btw chances are you have some sort of ground loop and want a ground loop filter. Or a 50/60Hz notch filter.

[@M6MDR]

Thank you. The project is battery powered and the humming is in the region of 250Hz which is very noticeable. At first I was using just a 100nF DC blocking capacitor in series with the audio signal line but every time the radio transmits, it would wipe out the audio signal completely - unless I went near the antenna or touched the metal box the project is housed in and then the audio would appear. I got round this by replacing the 100nF DC blocking cap with a 22uF electrolytic which seemed to cure the problem of the RF completely wiping out the audio or me having any effect on it when I go near it - however it has brought that nasty hum with it. I've just been playing with a circuit simulator where I've mocked up an active high pass filter with Op Amp but if I use an electrolytic capacitor for my filter, it complains about reverse voltage so I'm guessing they're not suited for the job. My concern is, if I add the low pass filter with a ceramic capacitor that I'll be back to square one with the RF killing the audio so they'll be no hum to filter out lol.... I am beginning to suspect that it is as you say, a ground loop going on. In which case, it may mean a re-design of my PCB to use some sort of star grounding? Guess I'm just going to have to prototype it up, suck it and see, as they say. :)

[@qch100]

Best video demo of filters ever.

[@weikiatteo]

hi. when you mentioned that the voltage across capacitor cannot instantaneously change because it needs time to chagre and then followed by saying if a sudden fast change voltage is pumped to the caps input it will instantaneously appear at the output side. i am confused by this statement.

[@jansnopek5569]

Yeah me too

[@D1ndo]

Yeah, if someone figured that out, please do comment. The sentence makes no sense.

[@DavidJomaas]

It will instantaneously appear on the other side because there will be close to zero voltage drop across the capacitor at high frequencies. It will pass straight throught. It's the voltage drop across the capacitor that cannot change instantanously. And it's the voltage drop across the capacitor that cancel out signal waves at low frequencies.

[@jasonw.2232]

So - correct me if I am wrong - the capacitor can act as a "variable resistor" depending on the frequency, whereby its "resistance" (capacitive reactance) decreases as the frequency increases. There's an inverse relationship there. The arrangement as shown in the video is very similar to that of a voltage divider, so the filter can be thought of in those terms. If, for a highpass filter, the capacitor is R1 and other - actual - resistor is R2, then with low frequencies, R1 should be relatively large compared to R2, so that there is a significant voltage drop across R1, so less of the signal makes it across R2. On the other hand, if the frequency is high, R1 should drop, attaining a value way less than R2. In that case, there is more of the signal to be dropped across R2, the actual resistor in this case. So the higher frequencies pass with less attenuation. (Remember that the voltage dropped across a resistor is proportional to the resistance value, as Ohm's law describes.) Certainly, a real-life circuit is not perfect, but hopefully the above provides some intuition. I found it helpful to draw out voltage divider circuits on paper and play around with different case scenarios.

[@pepe6666]

Jason W. Yes. Your word for the day is Impedance.

[@brownmonkeybananayellow]

Great videos. They're so clear! I wonder if you do video narration professionally. I do have a novice question though. I just watched this and the low pass filter video but I don't really understand what you mean by avoiding overloading the microphone with a high resistance.

[@VictorRivarola007]

You did an excellent job in explaining what a high pass filter does. Thank you. Now, that leaves me up with one question unrelated to high pass filters but related to your example, why are you using a high pass filter to remove the 9V DC signal, right after you've added it?

[@jbflores01]

WOW! that's the best clear explanation of these filters iv'e seen or read! thanks!

[@psyolent.]

i had to LOL at the 'shutup you got me for free'. thanks for the explanation

[@KayBeeOG]

I respect your sacrifice in Ravenholm my friend

[@psyolent.]

@@KayBeeOG A shepherd must tend to his flock. Especially when they have grown unruly.

[@tasspus]

Hello! Nice tutorial! Question: with a 2.2k mic and a standard USB sound card (2.2k mic input), what resistor should I use? 2.2 kOhm?

[@mikesamaki5063]

Best speech ever of an Oscilloscope: "Shut up you got me for free!" Great explanation of filters. Thanks a lot

[@RSP13]

mike samaki I think that was a function generator, not an oscilloscope

[@BeatRatio]

Great video! Very clear and well explained :) I'm thinking of building a simple HPF for music recording. Had a look at my mixer manual and it says something like: Source Impedance: 10K ohms or less Input impedance: 100K ohms Does that mean that the resistance I choose for the filter should be 10K or less? Cheers

[@hyperboogie]

Fantastic - very clear expanation I have an additional question - doesn't the resistance of the load itself interact with the capacitor and also affects the cutoff frequency?

[@jimfin12]

Fantastic videos.The best here.Definately.I would like to understand how you come up with a 20 mv p to p with the 9v and the 5000ohm resistor and what exactly constitutes a DC Bias and how is it made in a circuit.Cheers.

[@miketony2069]

awesome tutorial. clear concise and to the point I enjoyed watching your videos

[@jamesbaker5954]

how did you come up with 337pf from your equation. I really injoy , your presentations. I have watched all of them. I use a texas instrument TI-30xs. I get close to your answer, but the decimals end up in the wrong places.

[@jatza07]

Why DC 9V component is needed at the beginning ? small AC couldn't live by itself ? 0.1uF cap will cut DC off anyway. Thank you for explanation :)

[@danhle1032]

i think what's confusing is that it was never explained in the opamp vid that the mic provides AC and DC signals. it assumes we know that and that we want to filter the DC, which i haven't understood why

[@bilaldmx]

be cause the sound is an Ac signal , we just need Ac , so we filter Dc , and if we diden't filter dc we will have noise on the specker's, plus it can domage the specker's cause the dc is emplified with the opam's and can be 10's of Volt (this equal's domaged specker's ) and if we see the ac in the input it was just 0.002v and after omplification can be 1v or 2

[@danhle1032]

+bilal h that makes sense. Thank you

[@bilaldmx]

you welcome

[@bilaldmx]

and if you said so why we have the dc from the first position. then we filter it ?!!, the answer is this type of microphone needs dc voltage to work , then from it's result (generate Ac sound waves + dc offset) we filter dc , there is a microphones called dynamic microphones very used don't need dc so there is no need on it to have high pass filter or dc voltage this type of microphones are directly attached to the opamp.

[@soundsistem-masjid-narela174]

Sir,, I want to ask,,, The high pass filter and low pass filter mean that we can make a permanent without using a high or low signal cutting potential regulator. For example, I want to make at the end of the output the maximum low frequency is 150 Hz and the maximum high frequency is 2 khz 🙏

[@playingidiot7531]

3:34, finally I know why ecg's do that weird pattern when the leads are not connected.

[@hmauroy]

Pretty smooth explanations sir! Keep up the good work!

[@jonnyreh001]

shut up, you got me for free :DDDD

[@haley8004]

These circuit diagrams don't make sense. Where is the load connected? How can swapping the resistor and the capacitor make a difference if in both cases they're connected in series?

[@insylem]

Neat, watched your high and low pass filter videos. Did you make a band pass or band reject filter video?

[@JoshBrownPhotography]

Really great video, easy to listen to and understand.

[@Jnglfvr]

The "reason" the illustrated circuit at 0:48 is a high pass filter has nothing to do with the fact that the voltage across the capacitor cannot change instantaneously. It is because at low frequencies the impedance of the capacitor is much higher than the resistor and thus little voltage is dropped across the resistor. As frequency increases the capacitor impedance decreases, and thus more voltage is dropped across the resistor. The opposite obtains if the output is taken across the capacitor instead namely at low frequencies the high capacitor impedance is reflected in high output voltage and at high frequencies the low capacitor impedance results in low voltage.

[@rong111y]

know anyhow to convert the voice signal from a microphone like the one in your video to Digital? by the way, Love to watch your easy understanding tutorials, good work.

[@massimilianogilli1164]

Can you elaborate more on the 100k resistor you put? You basically want the microphone to see a high impedence? If so how do you define high? Do you calculate the current as 9.2/(100-10^3) and tune it somehow?

[@sandychristablet8255]

in the last example in the op amp, I really do not understand the part in the high pass filter when adding a high resistance 100k in order to not overload the mic for amplifying, thats confusing and what happens if you decrease the resistance and increase the capacitor as long as you get the desired cut off frequency , please help thanks

[@ComboSpartan]

Me too got confused at the same part! Have you got the reason for the same yet!!

[@hyggeligt007]

This may be a late reply, but in my understanding the high value resistor serves as a current limiter. The microphone may not be designed to handle very high current values. More information here : en.wikipedia.org/wiki/Current_limiting

[@bajojohn]

I think it’s the other way. The voltage at the + and - nodes of the op amp will be the same. Since the gain is Vout/Vin, and we know that the gain is 10, the output will be 90V theoretically. Practically, it’s just maxed at 9V. By adding the resistor, it reduces the voltage at the + node, which reduces the voltage at the - node. I suppose we could just lower the microphone voltage, but you would need two power supplies, which is inconvenient. So yes, the frequency cutoff would be the correct value, but the resistor value would not divide the voltage enough so the output wouldn’t distort.

[@jmrt21]

I think the gain in this case is 100,

[@fosheimdet]

I don't understand why this setup should produce a different result than the lowpass filter. Doesn't the same explanations apply in both cases? What difference does the placement of the resistor make?

[@Vtrontv]

Excellent videos! thanks for uploading.. but i have a doubt i want to make a filter for my radio so it will give very good sound quality, so is it possible to make a circuit like this to filter just 88-108 Mhz? help appreciated thanks !

[@kennewickman5086]

I'm pretty sure I just watched another video where the guy put a guitar knob where the resistor is and that makes it so that the frequency is adjustable. Is this correct?

[@yufliu]

I'm confused as to how you got a 20 mV peak to peak signal from the 9V and 5K resistor. How does the math work for that and why do you use a 100K resistor for the HP filter? How does the math work for that? Why not a lower resistor or what is the lowest the R value could be before it overloads the output?

[@distortedmist]

i have the same question :P

[@girishjadhav6286]

@@distortedmist Signal Generator provides the 20 mV sine wave and the DC voltage provides the necessary offset.

[@coolg963]

if your hooking up a highpass filter to a set of tweeters, would the resistance value be the resistance of the sound drivers? because I assume you don't need a extra resistance for one of these circuits right? and also how do you put strain on a source? you mentioned it a couple of times in the video but where would I be able to learn more about that?

[@earlibee]

Hey afrotechmods, I always use just a 2.2uf capacitor(connected in series) to produce a high pass filter to my tweeter. No resistors are used. It worked very well. Are there any disadvantages of doing this?

[@midnitelitecompany]

im using a velleman 7 watt mono amplifier as a guitar amp. im running two 4 ohm speakers in series, and there is some low end thats slightly overdriving the 4" 10 watt speakers. how or what capacitor and resistor valuea should I use? and can I put this filter on the lead of the first positive input on the first speaker in the series? thanks!!! AWESOME information but slightly above my math skills lol!!

[@00Skyfox]

In something like the microphone amplifier circuit at the end, how do you determine what will overload the microphone's output and therefore determine what value of resistor to use?

[@abcddd580]

4:00 why do you even need the 9v DC offset? a microphone itself creates an electric signal from sound right?

[@madhuradharme9131]

No Microphones is just a capacitor whose capacitance change according to vibrations created by sound waves.

[@abcddd580]

@@madhuradharme9131 Ok after reading up on types of mics, the operating principle depends on the microphone. Some microphones operate as sound pressure-dependent variable capacitance as you mention, and others operate on induced voltages in a coil moving along a magnet. I guess he uses the capacitance type of microphone (condenser/electret) instead of the one I was thinking about, in which case it would make sense that he would need to power it with a power supply. Thanks!

[@thisguy8943]

Anybody here can help me? I play bass guitar and I want to make a hpf with a cutoff frequency of 50Hz and another with a cutoff of 90Hz. I'm not great with math so although I understand the equation presented at 1:43, I don't see where he got the resistance value.

[@joegoren2133]

Why do you say the 3dB cutoff point is 29%? I thought -3dB was 50%

[@baqirzaidi8025]

thanks a lot sir .........and love the way you teach!!!

[@MrMember12]

You are the best! This is what I was looking for... Thank you a bunch

[@orbita1]

What i didn't understand is how, when hooked up to your mic, does this remove the offset. i can't visualise it. I thought the high pass filter here is purely for audio preference purposes. I didn't know that the mic's output oscillates over it's V_in, so now i know that we need to remove the offset (and as you have, you've got the signal to oscillate at 0 V). I'm trying to build a circuit similar to this, but i want a high pass filter to remove things like footsteps. Originally i made the cutoff F to be about 160 Hz, but now i'm worried to rethink the schematic, since i may not be accounting for the dc offset removal. Any help would be appreciated. Great videos too, helped me a lot during my degree :)

[@Pilot92438473508]

It works because a cap blocks dc.

[@countrpoint9072]

Thank you for your awesome videos!

[@quirmche]

Boy, that beaver really took a pounding!

[@igrewold]

Cool man, thanks. But how do you make a filter that works on just 300Hz to 3,000Hz (3kHz)? In other words, it filters out anything 3kHz. Such a filter might be useful for listening Human Speech, older recordings & such.

[@TheBaconWizard]

What would be the best way to go about having both high and low pass on a signal to leave you with a middle-range band pass?

[@car87san]

@Afrotechmods Why wasn't the 10kHz signal completely blocked at 2:43? If the circuit was made for a 30kHz cutoff?

[@davidconstantinneacsu6164]

Afrotechmods you are a great teacher , thanks for the lesson , maybe in future you will make a video about preamplifiers .

[@devangec]

Thanks for the video. With a square wave input why does the output of the High Pass filter spike where the Pk-Pk voltage at output is > Pk-Pk at the input?

[@Tordek]

Is there a reason why you use a rheostat in the end, when feeding the output to the speaker, instead of a potentiometer as a voltage divider?

[@deanwsmith1]

Your video on lowpass filters is blocked in Germany. I get this message:.. Unfortunately, this video is not available in your country because it could contain music, for which we could not agree on conditions of use with GEMA. Can you upload it again ??or tell me where I can watch it . Thanks in advance (great tutorials)

[@Kdon15]

dean smith Same for me :/

[@ana-maria62245]

Hello sir! I have a question. What do you mean by: "Having a high resistance value will ensure that I don't overload the microphone's unamplified output"? Isn't a high resistance on an output, an "overload" itself?

[@rlrsk8r1]

Ana-Maria Chiper No, if that resistor weren't there, a lot of current would go from the microphone's output straight to ground. With the resistor there, very little current can flow straight to ground, and must instead flow into the op amp.

[@zynthos9]

+rlrsk8r1 An op amp's inputs take in 0 current, is that not a fundamental rule of op amps?

[@perldition]

I miss you. Hope you're doing well!

Nice tutorial! Do you think it's a good solution in a car to solder this thing right before the mid-range speakers? If it is, what values (C and R) do you think the best for a 100HZ HPF? (Or is there a better solution to filter amplified signal?)

Please answer mee

[@fantuznet]

interesting that you mention the passive/reversed configuration with a schema of RC/CR and DC behaviour

[@fantuznet]

well I will watch even the High pass LC filters

[@215alessio]

what about not using the extra resistor and use the imput resistance of the opamp to calculate the capacitance?

[@balkey312]

you are an incredible person

[@reviathon360]

Can you do a video explaining the highpass filter using the OPAMP?

[@MINHHOANG-hl7gp]

hi ,can you make a tutorial about bandpass filter

[@horimiyarawstyle]

Plz can make another video of HPF but using transistor ? Every active circuits are using opamps but I need explanation with Transistors

[@g00glian0]

How do you determine what is high and what is low? Say I use a 10K resistor and a 10uf(.00001) capacitor with this formula... it comes out to 1.59Hz. That isn't high at all. Or is it all relative? Would this still work? Or would it be low pass instead? So confused...

[@SkyniaSound]

can you advise on how to incorporate a pot to change the value of the cutoff frequency?

[@personal7681]

I understand the 9V DC because that is the supply voltage. But how did we get 20mV peak to peak?

[@zieyadahmed5001]

+Personal voice signal

[@hbayumy]

Excellent tutorial as usual, but i got 1 silly question, how did u get those 20mVs p-p ? i mean, how did u calculate that ? Thank you very much :)

[@stabgod]

+Mahmoud Bayumy The 20mV p-p signal is pretty standard for an electret microphone. Connect an oscilloscope probe to the output of a typical electret microphone and then make loud noises into the mic. The scope will reveal really small signals in the 10 mV to 30 mV p-p range.

[@hbayumy]

stabgod aha, thank you very much.

[@SharkyLV]

you are the best! you really help me with my course. thaankk youuu

[@sajan223]

I have seen your video of "Voltage divider tutorial" I still don't know what kind of resistor is needed for high pass filter.

[@Muck-qy2oo]

What if you have a tank circuit? I mean a tank circuit as a source?

[@tafakadere6018]

I think he means the voltage within the capacitor can't change quickly so anything that is too quick for the capacitor to use just goes through it.

[@silverstream314]

I love these videos. Keep it up!

[@MephistoRolling]

Great videos, if only i knew about how to pick the right resistor! :P

[@kka10001]

Don't that come out to 530pf or am I doing something wrong.

[@alitou001]

I enjoy these videos

[@zynthos9]

An op amp's inputs ideally take in 0 current yes? So where does the current to the load (headphones) come from? Is it supplied by the +/-9V supplies on the Op amp itself? Also how would the amount of current be determined? Simply by whatever the headphones draw, regardless of the resistance of the 10k pot you have? Also how do we know how much current goes from the output through the 100k and 1k resistors (used to set up the gain) to ground (because ideally none can go into the inverting input of the op amp)? Thanks.

[@Afrotechmods]

+Zambia95 The current to the load comes from the power rails. The current will be determined by what the headphones draw plus a small amount of quiescent current that the opamp needs to use internally to operate.

[@zynthos9]

Afrotechmods Thank you. So is the current through the resistors used to set the gain simply wasted power that can't be avoided?

[@Afrotechmods]

***** Yes but it's only going to be a tiny percentage of the total power loss.

[@zynthos9]

Afrotechmods Thank you

[@Nadrealis]

I have a question. Why do you have a 9 volt DC offset if you're only amplifying the 20mV input signal?

[@countryfresh2036]

Thanks for showing how these.work im building my own crossovers for my car audio this helps alot

[@wilsonlih0814]

Excellent video, is super useful. thank you so much. like all your video so much

[@Warndog9]

Would building two of the same feq cutoff filters back to back make the frequency response have a steeper curve?

[@rlrsk8r1]

So I don't have a power supply that can provide +/-9V. Could I crank it up to 18V and use a 50/50 voltage divider, thinking of the "ground" rail as -9V and the "middle" of the voltage divider as "0V?"

[@burgersnchips]

rlrsk8r1 Yes provided your voltage divider uses low enough resistance value to create a stable "virtual ground"

[@burgersnchips]

rlrsk8r1 Also would be a good idea to use a couple of large value capacitors parallel to the resistors in your voltage divider for a more stable virtual ground.

[@___xyz___]

4:37 oh phyeah well ill sho wyou .. hold my beer!

[@xlilsasuke4x]

Why not use a voltage buffer instead of the 9v and 5k resistor?

[@forester_overland_nz]

i envy you for having your own oscilloscope :)

[@16BITMEME]

Your channel is gold

[@lucasmontec]

Why did you put the 9V to the Mic to place the 20mV above a 9V dc and then used the low pass filter to remove it?

[@ecniv5700]

It seems as though a capacitor before the resistor would give you a high pass filter vs a low pass filter which has acapacitor after the resistor. Is this true?

[@ganeshkumarshetty]

Sir, how to get -9V for opamp IC? Can we use GND instead of -9V? Please suggest

[@sharmaneeager1927]

If I use this to a speaker's output while parallel with a sub will it affect the sub ?

[@worldonscreen]

Great explanation 👍

[@sajan223]

Thanks for explaining. 4:22 sek. I still don't get it, how do you know ?? What kind of resistor is needed to the high pass filter. 100K resistor makes 20 mV input on the amplifier?? I don't get it. Please help.

[@RA4FOC]

Nice Job! Nice LTSpice soft.

[@elijahmerrill9045]

I wired three piezo discs in parallel and tried to put a high pass filter and a low pass filter on the output, but no sound came through. Can anybody tell me what components I should use for a 60 hertz cutoff high pass filter and a 12 k low pass filter (for an acoustic guitar application)?

[@RandomSTUFFzors]

If a filter can be made using capacitors and resistors, why is it common to see frequency dividers in speaker enclosures that have capacitors and coils instead of resistors?

[@isrxi]

BTW . Your videos help me alot ant make more of them ;] (sry for english)