I don't think the phrase "Half a bee's dick" has gotten NEARLY as much use as it deserves

Brilliant, Dave. Wish you did more of this content. Bring back fundamentals Friday!

@EEVblog Hey Dave, I LOVE your videos! Hands-down... the best in electronics on KZfaq! I benched this circuit IDENTICALLY as shown including values for components. (I even used a mini breadboard) to DUPLICATE “EXACTLY” what you used in the video. I used a Switch Mode Power Supply configured for 5v. (Just as you showed in the video). However, I couldn’t replicate your ripple results. COMPONENTS: Switch Mode Power Supply Volts: 5.00 (5.001v Actual Output) - Measured using: Keysight 3458A - 30min+ warm-up Keysight U1271A R1 (Base Resistor) = 1k - 1/2watt - 1% (996.83 Actual) - Measured using: Siglent SDM3055 - recently calibrated - 30min+ warm-up Keysight 3458A - 30min+ warm-up C1 = 470uF 35v (486uF Actual) - Measured using: Siglent SDM3055 - recently calibrated - 30min+ warm-up Keysight U1271A RL (Load Resistor) = 270 - 1/2watt - 1% (269.94 Actual) - Measured using: Siglent SDM3055 - recently calibrated - 30min+ warm-up Keysight U1271A Q1 = BD137 - (not a BD137G) ------------------------------------------------------------------------------------------------------------------------- BD137: R1 Voltage = 57.593mV = 0.057593v (Verified with the above 3 Multimeters) RL Voltage = 4.2747v (Verified with the above 3 Multimeters) I1 = 57.78uA = .00005778A IL = 15.83mA = .01583574A hFE: 274.069574 Of course, it smoothed out the ripple nicely. However, my ripple numbers are considerably higher than yours. I used a Keysight DSOX2012A to take the measurements. (Essentially the same O-Scope you used in your video). - I wish we had the ability to attach photos here on KZfaq. One thing I would like to point out that when I measured, I used a ‘M’ BNC Oscilloscope Probe Adapter & a “Pomona” ‘F’ BNC to Banana-to-Hook Test Leads on the Oscilloscope Probe. This is the best possible connection to give the “FAIREST” test possible so that external Transients were not introduced and won’t skew the measurements. This is why I didn’t use the supplied Oscilloscope Probe “Ground Wire” to Alligator clip. Ripple PRIOR: (Raw Power Supply output) Pk-Pk: 40.92mV Ripple w / “Capacitance Multiplier”: Base Resistor R1 = 1k (996.83 Actual) Pk-Pk: 17.64mV Base Resistor R1 = 10k (10080 Actual) Pk-Pk: 36.17mV (Pk-Pk went up, (by DOUBLE) NOT Down) Using the EXACTLY the same parts & essentially the same oscilloscope to take the measurements, how were you able to reduce the Ripple down to: ~ 2.5mV Pk-Pk? Something doesn’t add-up here. BTW, I agree with you, I don't like the term "Capacitance Multiplier" either. It's really just an RC Filter.

Thanks, Dave, for all your efforts. I retired in 2013 after 34 years on the road in the US and Canada as a Biomedical Field Service Engineer. Like many old guys, I have a pretty decent wood shop, but I got to looking at my pile of electronics stuff, collecting drifts of sawdust, and decided to get back into it. Your videos are a great help, renewing what I used to know, and learning new stuff as well. A great help in keeping the old brain cells moving.

Wow, this video just saved my ass... I had 350mv ripple on a crappy power supply at work and it was messing with some of my testing and this circuit got rid of it all! Thanks so much Dave! You're a real life saver!

Nice explanation, Dave. There is a trap for young players here. If the input voltage ripple amplitude exceeds Vbe-Vce~=0.6V, this circuit doesn't work properly anymore, because the collector voltage drops too close or even below the emitter voltage. At that point, only the base current makes it to the output and there is no current gain anymore. An additional resistor across the capacitor can be used as a voltage divider to solve this issue. This will lower the base voltage, which lowers the emitter voltage, and allows the input voltage to drop lower before there is no current flowing from the collector to the emitter. I ran into this problem with a low power, high voltage boost converter that had more than a volt of ripple.

we usually just hire an intern to watch the scope with one hand on the regulator's Vout control. They've gotta have good reflexes though. And coffee.

This type of video, where one "building block" is explained in detail is my favorite.

Dave is a knowledgeable teacher. This is one of his more direct and precise tutorials. Informative and enjoyable.

In the '90s Technics (then Matsushita Electric, today Panasonic) called a variant of this topology "Virtual Battery", claiming a supply to analog stages almost as clean as a battery. They used a big cap and a mosfet, and there was a switch in place of the resistor. It was used in their HiFi components.A very simple idea, but it does in fact work fine.

That's the best and most visual explanation of the Capacitance Multiplier i have seen so far.

So good you could do one for each day of the week. Methodical Monday, Tuition Tuesday, Whiteboard Wednesday, Theory Thursday, Fundamentals Friday, Strap in Saturday and Sod off it's Sunday. Thanks for all the great content.

For years I have been using 3 different names for this circuit among my colleagues. 1. Capacitor Clipper 2. Ripple Clipper and my personal favourite: 3. Ripple Cripple (May not pass PC 'certification')

Hi Dave,great video. I used to service electronic engine analysers many, many years ago. One brand of analyser, proudly made in Sydney, use the capacitor multiplier in its pos and neg supplies to the scope display. They used a 15inch TV B/W picture tube with magnetic deflection. The scope did not run at TV scan frequencies but swept at 10Hz up to over 1kHz. So the load caused by the deflection circuitry, apart from being quite large, was also not of constant frequency. The multiplier circuit work a treat and was made up of 4700uF and good old 2N3055 and MJ2955.

I became a cropper trying to use a linear regulator to remove the ripple on a DCDC converter, only to find that the PSRR for the reg wasn't as high at the frequencies of the DCDC switching. This circuit might just be a solution! Cheers Dave!

that "I only give Negative feedback" on your T-shirt is epic

12:30 - This circuit also provides a soft-start as C charges on power-up

s. 578 in The Art of Electronics :) And if the ripple is in the MHz range, you can add a ferrite bead to the base lead of the transistor.

I used these (BJT implementation) for the power supply rails feeding VCOs in PLL synthesizer applications many years ago to reduce oscillator modulation due to power supply rail ripple/noise, thus improving phase noise in the design situation.

Very interesting circut, have spent 40 years in electronics engineering and this is new to me. Thanks!

In telephony, this circuit ( Rb, C, Darlington Q, and Re) are used as an "electronic inductor." (Re is the load resistor - RL in Dave's circuit). If you measure *AC* impedance from V+ to ground, (or do the math for this circuit) you'll find that at low frequencies, this impedance is Re - which is typically small. At high frequencies, the impedance is Rb, which is larger. In-between, the impedance goes up at 20db/decade - the same slope as an inductor. This assumes you are below the frequency where Miller capacitance is a problem - above that frequency, the impedance will start dropping again. This circuit was used to replace the inductance of the ringer coil when newer phones came out. The phone lines were specified to require a certain amount of inductance across the leads when on-hook. When big mechanical ringers were replaced with electronic ones, they still had to keep that inductance in the circuit - hence the "electronic inductor" circuit came to be. The effective inductance of this circuit only needed to appear in the audio band. When using this circuit for ripple reduction, I've heard it referred to as a "rip-red," i.e. short for "ripple reducer." In that case, Re is replaced with the load you're reducing the ripple to.

It's 4:30 in the morning.. I was wasting hours of searching through many of powerful linear regulators.. But all too expensive and space consuming... I also really needed a soft start feature too. I was close to alcoholism, but then a saw this video, now I'm in love with you!

Dave I have the early stages of dementia and you should have lost me in the first 5-10 minutes of the video, but had me right up to the end m8. That speaks volumes about the effectiveness of your teaching. This was nothing short of fascinating, and as it happens it's a small piece of the puzzle I'm trying to figure out and put together in a correct way so that it actually works. Liked and Subscribed sir. Thank you.

At home with The Virus and going back through some of these videos, they are excellent. Thank you Dave.

I once did the opposite: an active capacitance cancellation circuit. I used it to cancel the capacitance of a photodiode so that it could run faster as a data receiver. Without the circuit, the bandwidth was limited to 200Hz. With the circuit, I could get the required 32kHz. It was a long range infrared remote control receiver.

Hands down the most informative long-term active channel with both great insight in complicated stuff but also content for a beginner like me.

Finally an electronics presenter who speaks my language. "Down to bugger all values". Now an Aussie like me can understand that. 👍

Man, I wish I had professors like this in school. It was like being taught by the Crocodile Hunter. But instead of learning about crocodiles, we are learning about the anatomical size of bee genitalia. All the fun aside, this is a great video. Thanks.

Glad you're still doing these. They're fantastic.

The fundamental content videos are always nice, thanks for showing!

Not only very good teacher, also you are very very very very gooood teacher.... Thanks all of your works!!

All that was handy, I'm just staring at my scope watching a 7660 bouncing my supply lines and Dave pops up with this! Cool.

Great description Dave! In the "old days" we called that a ripple stripper, not a capacitor multiplier.

Smashing video dave :-D I've seen this configuration a lot in basic linear power supplys, but never thought too deep about the filter magnifier effect. A handy ripple reducer as long as you don't mind a bit of voltage loss :-).

You forgot to mention that the output of the emmiter follower will be at least 1 x vbe lower or 2 x vbe for a darlington. You may need a diode to protect the gate and discharge the capacitor when the supply is turned off

An emitter follower with large bypass capacitance at its base and emitter (presumably this circuit would have bypass cap at its output) can be prone to RF oscillation due to stray series inductance if not laid out very carefully. It wouldn't hurt to add an extra SMALL resistor (like 10 ohms) in series with the base to suppress such oscillation.

I can’t thank you enough! Sharing your knowledge is such a big a gift to the EE community.

Thanks Dave! Even after getting my BS, your fundamentals videos continue to educate. School can't cover everything :)

Great video Dave! Your building block circuit tutorials have been a tremendous help to me.

Every time I watch one of your educational videos its like the sun shines on my brain and the fog clears immediately. Thanks so much

EEVblog one of the best on youtube, excelent !!!

This was a very interesting video that I really enjoyed. Thank you for sharing. Personally, it would have been nice to see the MOSFET in action as well!

That's reassuring. When you called it a capacitance multiplier my first thought was "that can't multiply capacitance!" I'm glad to see the name is a misnomer :-)

AWSOME tutorial. Love this content. Practical, easy to test at home and above all genuinely useful for so many applications.

its a really smart way of making your SMPS "linear". Probably a nice solution for compact audio amps and lab psus.

I can't find the link of the full demonstration video of regulator voltage you mentioned I love all your videos !!

Great info as always, and Dave's colloquialisms always give me a chuckle.

You are a very good teacher taking all aspects as examples, why things not always goes together. Excellent!

Brilliant, thanks Dave..... Love these fundamentals..... Useful circuit.....

Actually it should be called a load multiplier. The effective load value that appears parallel with the capacitor is beta×output load. That is why it is very effective as a ripple filter. I actually used something like this in a car audio application to filter alternator ripple to a car audio power amp. You could hear the alternator ripple comming through the speakers as you reved the engine; additional to the capacitor I used a 12V zener in parallel. Generally the alternator ripple is riding above 12V.

I love these video lectures he gives from time to time.

I've been using these in designs requiring ultra low noise supply rails for 30 years. They are superb if you get your calculations right.

26:00, the Op Amp also has its own power supply rejection ratio, if its positive supply is the same ripple injected power supply going into the multiplier, then the ripple rejection will only be as good as the op amp's PSRR.

You're a very good teacher. :-)

I love extrapolation of different topologies and calculating transfer characteristics. Good video Dave.

Just from 10 your videos, I have learned way more about electronics than I did in my entire lifetime, including the university. Thank you.

60fps, a real whiteboard, good old Dave. More this :)

Excellent tutorial Dave... Been a while since you did one.... We need more.

Another super video from Dave ! Thank you for your contributions to our understanding of electronic circuitry.

I'm so happy you just stream right to my bench to drop off new practices with that clever shirt. Right as I'm designing power supplies. What a day to live. Its no Free Energy but I'll take it! Thanks Dave

NPN transistors for the win!

I really missed these videos! And well... that was (maybe?) new to me, naming is indeed as you said tricky... It makes sense though, plus the transistor as a primarily a current source has a really high noise rejection by itself... Yeah! Cool stuff! BTW... I really don´t get why it would work with a MOSFET, you have to run it in the non linear region and it would be rather messy.

I noted this circuit some time ago and only recently had a change to test it on a simple linear supply to reduce the 100Hz ripple. To cut a long story short, I found that it wouldn't work when I made an RC filter with just the reservoir capacitor - it had to be used on a 2nd capacitor (actually, an RC filter) placed after (i.e. downstream from) the reservoir capacitor. If the values of R and C are chosen well, it works like a charm. The ripple voltage reduced from 4V at 100mA with no filtering, down to 150mV. This was while using just a single 2N2222, just to try out the concept. I'm sure I could get better with a Darlington pair setup. In retrospect, I should have realised that without a reservoir cap feeding this super-filter, there is no source of stable supply voltage to feed it. Anyway, that's my simple-minded rationale. Thanks again, Dave - I absolutely love this "fundamentals" series because I learn so much. I'll never get enough of them.

How interesting! I wondered what the world you were doing for the first few minutes until it clicked. I’m going to try this with a power FET...

Ok. I gave it a try and it worked, but there was a significant voltage loss with a 1k R. Using a smaller R raised the voltage back, but the ripple also returned. Any suggestions?

Basically good facts all along. You even showed that the breakpoint frequency did not change as expected. But your move from passive to boosted solution left a bit of a gap in cost/benefit respect. Too bad, the low drop-out regulator is the one that has miserable input ripple rejection. But guess what - the current booster is no better if the voltage head is lost. As you talked about the 300 mV drop on the regulator case, you did not emphasize that single emitter follower has some 0.6 to 0.7 V drop, depending on load. A Darlington tends to have 1.4 V drop. A “Fetlington”, i.e 2N7000 has about the same threshold voltage and big MOS FETs 4 to 8 V. You could do better with depletion mode FETs, but that is already pushing the state of the art. Traditional voltage regulators when given enough head voltage do a decent job in reducing ripple. But if the input is for example 8 V peak and 7 V ripple bottom, even the traditional 5 V output regulators are at the spec limit. The 2 V head requirement is counted from the ripple bottom...

Great video. When you were discussing the transistor/ Darlington current amplifier, my first thought was, why not use an op amp. I am happy that you discussed this at the end. Bob

One of the best instructors I have seen..!! You keep it interesting and moving at a good clip..!! Great stuff..!!

Dave , you're the man 👍

What power does a fet or bjt dissipate in this circuit ? Just the ripple voltage x current or are there more factors than internal resistance / wiring.

Thank you Dave. Just what I've been looking for after days of internet searches including looking at expensive bulky Pi filters.

I like your description of the circuit in terms of blocks.

Nice! Could we use LC filter instead of RC?

"Half a bees dick" LMFAO! That great! Another great engineering lesson.

I'm not at this level yet, so I don't really understand what you're saying, but this video is still great to watch! You're so stoked about this!

Great explanation Dave! These video's I enjoy the most next to your teardown vids.

"Active low pass filter" sounds better than "capacitance multiplier"

The Sziklai pair is pronounced like "sick lie"... Sziklai, not slikai. And its benefit is, you're only dealing with a single Vbe drop (and the Vce drop, much lower at saturation, of the other device). Also, it generally performs better than the Darlington in most applications, but it's more expensive to produce monolithically (lateral PNPs in a standard cheap bipolar process is pretty much a no-no, so you need a much more expensive complementary process), hence why you don't see NPN/PNP-type Sziklai pair devices floating around Digikey.

Thanks for covering this, first time hearing of this topology, really cool!

Fundamentals videos like this are what drew me to the channel and caused me to subscribe. They are very helpful for the hobbyist.

You could always add a zener diode in parallel with the capacitor, then you will have basic voltage regulation, sure it's not the best but for most cases it works well enough.

Can you go over charge pumps next?

its like watching Horowitz and Hill the movie, my all time favourite electronics manual in video form. Love this stuff Dave.

That was super useful, thanks Dave. I was just messing about with a similar circuit and the ripple from the input was getting magnified by the output. Now I have a way of figuring out how to filter that mess.

The only thing is that voltage drop is really high, which compromises the efficiency of DCDC converter

but how does it perform under a LOAD?

Dave for president! Your video's are a great contribution for the community. Your cheerful tone is a nice gift for every one.

Awesome! Love your circuit demos! I learn a lot with them.

What even works better is a RCRC network because you actively make a 2nd order filter (Q=0.5). Another method is forming a 2nd order sallen-key with a transistor.

How the hell youtube know Im dealing with that right now ?

Thank you so much, I spent 10 hrs trying to "cure" my ripple problem........ gave up and found this, built the circuit and it worked perfect the first time........ THANK-YOU....... and it happend to be a Friday! LOL

Excellent Dave, the name you're looking for is APF or active power filter.

You can make it into a voltage regulator at the same time by adding a zener diode from base to ground.

so why not use an inductor instead of the resistor... ?

Learned something new today! I have some sensitive things I'm trying to drive with a DC-DC converter and hi-freq ripple is killing me. This made my day!

Linear regulators have very efficient ‘outboard’ transistors built in. They also have loop compensation and thermal regulation along with current limiting and ripple regulation. Saying that they are inadequate is simplifying PSU IC choice. Look at Linear, TI etc. They are typically better than the solution you present. Some even have the pins for doing outboard current sharing.

I wouldn't exactly call ~35dB (4:24) a _"horrible"_ (4:45) reduction.

The capacitance is multiplied, but the resistance is divided, having no net effect on frequency response

Nice tip, great demonstrations and awesome explanations! I was also missing these basic electronics videos ;). Excited to try it this weekend :D

I enjoy your tutorial videos very much and hope you decide to get back into those. You are a gifted teacher