Hey Dave! I don't know if you check comments on old videos but I wanted to mention some things from my experience at work building amplifiers for signals in the 50nV range. Based on Jim Williams' work, I started using steel cans for my testing. I put my little amplifiers into Altoids mint cans with a voltage divider built-in so I can inject a signal and I have no problems with 60Hz (USA) mains frequency showing up in my measurements. A 9v battery and the amp fit nicely, and I can solder directly to the tin for a solid ground. I have found that die cast and aluminum boxes don't work as well as steel mint or and cookie tins. Ferrous material really helps with shielding! I have been able to show a 100nV signal on the DSA at work with no trouble! Also, I use an HP DSA for spot checks but final plots are done with an RME audio interface and Matlab, which easily beats the HP signal-noise specs. Thanks, and keep up the good work!
Two years ago I watched your OpAmps tutorial video as a 2nd year B.Sc. student preparing for his Electronics class exam. Now I'm working on my B.Sc. thesis and again hats off to your great explanation sir!
Hey Dave, I've been sick for the last few days and I think I might have spent about 90% of my waking time watching your videos, please keep them up they're brilliant :)
Excellent post. Many of the terms used in datasheets aren't obvious and I appreciate you taking the time to make some sense of the more obscure ones that I may incorrectly gloss over when selecting components.
Thank you so much for these op-amp tutorials. I have been building circuits using op amps my entire life, and I never had a true ( thorough) understanding of how they work and how to design circuits with them- until now, seeing your videos. Thanks again.
This video is excellent Dave. Don't be fooled by the apparent little interest of the people who don't get it yet. We want the followup :-) Thanks a lot.
This video couldn't have come at a better time for me Dave! Thanks. FWIW, last year researchers used layered graphene to determine that "1/f noise becomes dominated by the volume noise when the thickness of the films exceeds ∼7 atomic layers (which corresponds to ∼2.5 nm). The 1/f noise is the pure surface phenomenon below this thickness." [arXiv:1211.5155]
So...,I'm closed at home because of coronavirus in Spain at the order from our goverment. But, with gems to learn like your videos, i hope not to be bored much next two weeks. Thanks for this videos Dave!.
Great old video Dave, after watching one of your videos years ago about the HP DSA I was able to find one at some government auction, GLAD I did ! Wish you would do some more vids using these ol boat anchors.
I am surprised because Dave produces a very clear audio. I recommend to use headphones. It helps me sometimes. Not that I ever needed them on one of the EEVBlogs.
Great video. You answered so many questions I had about my HP3562A analyzer. I would love to see you make video about dropping in the high performance modern lower noise parts in it. And then see you go through calibration. It would be a great video mate!
Speaking as a physicist (to be, at least), I have the urge to add another clarification to the video. Namely: physics ALWAYS makes sense - it is, however, sometimes counterintuitive. There's a huge difference. Great video though, thanks Dave
It generally takes well under an hour. I can literally watch the counter increment on every page refresh. And it usually takes less than a minute after release for someone to comment!
Even though I don't suppose I'll ever use this information, I find it highly interesting. You have quite a nice way of explaining things. Speaking of noise, perhaps an upcoming video could explain the different types of noise you mentioned at 13:00. Something of a comparison of each type, how they are generated, and how different components (resistor vs. cap vs. inductor vs. transistor etc.) are affected by the different noise profiles. Maybe even techniques to deal with the different types.
Really nice video and good old intrument there.. One thing you could have shown was the effect of the cable+box without any opamp active. That could give better base level for testing the opamps instead of direct 50ohms termnation.
Actually it possible to measure the noise of an op amp with only 10nv/rtHz if your op-amp have some gain. For example, if your op-amp have a gain of 10, at the ouput, the noise will be arroud 100nv/rtHz ! Because this is the noise defined to the input of the op-amp and it will be amplified by the op-amp.
I'm really looking forward to see the "optimizing the 35660A with modern input opamps"-video! I hope i''m not alone! =) btw... i really liked the whole tutorial, it gave me much new knowledge about op's! Thank you!
That was such a fun vid! I learned a lot, and I loved that you used the DSA we had fun watching you troubleshoot and repair. You'd make a fun character if there was ever going to be another Mad Max film (one of my favorite movie franchises, btw).
There are many sources to consider if you want to do this properly, I just wanted to do a quick test to see if I could show the difference between opamps. This is ballpark stuff.
I would never take it to the bank! I recon I make some sort of mistake or slip of the tounge in most videos. I did in this one, hence a few annotations. The off-the-cuff nature and the difficultly of checking ones own work during editing means mistakes will always slip through.
The reason I love this channel, is that you can take everything that comes out of Dave's mouth to the bank. Too many people try to bullshit their way through a video like this. Great video!
In case anyone else goes looking, the component Dave used at the end is the NE5534, not "NA5534". I have a hard time distinguishing his As from his Es. I first heard Dave on the AMP Hour podcast, and for quite some time I thought he wrote the AAV Blog.
Very good explanation! It was a good help ;). I need to amplify the output voltage of a 1kHz notch filter, uVs... to measure a SINAD in an audio Amplifier. But I'm having troubles with the noise. Now I'll try reduce the resistors values and chose an op-amp with a reduced noise, now the ne5532... Many thanks! My Channel is in Portuguese sorry... Regards, Hugo.
Excellent presentation! I do have a couple of questions, however (warning: long post): why doesn't the DSA use its own calibration data to remove its average noise contribution from the display? Much like 'taring' a scale? The math is straightforward enough as demonstrated by your own calculations at the cursor frequency and SO shouldn't be all that taxing to the analyser's CPU, so why doesn't the DSA do that for you at all the points? That would be very convenient, yes? My second question is: why does the displayed 1/f frequency curve taper-off at the lowest frequencies instead of increasing with decreasing frequency as all 1/f curves do? Surely this is an artifact? Even with _two_ data points it should sweep much higher than seen on this video (as at f = 0 Hz it is theoretically _infinite_ [but would take an infinite time to measure] :). Is the DSA bandwidth-limited at that end even with DC coupling, and even though it is spec'd from _DC_ to ~100 kHz? And just a note: coax shields are generally pretty good as _electrostatic_ shields, but not so great where _near field inductive_ coupling is concerned, where there's a measurable AC _magnetic_ field gradient penetrating the shield into the space between shield and the centre conductor? Same for die-cast aluminium boxes. Possibly a good mu-metal enclosure (at least for the DUT and wiring), may reduce that 50 Hz peak somewhat? Give it a try and see if it makes a difference. Mains frequencies (and harmonics) are the bane of my applications, VLF/ULF/ELF radio receivers. The one I'm designing at the moment has a passband beginning well inside that 1/f curve, with the upper stopband beginning at around 40 Hz. Even so, 50 & 60 Hz mains frequencies can be strong enough to swamp the preamp and it is nearly impossible, it seems, to get away from it - short of moving to _Antarctica._ :( As far as 1/f specs go, in your experience which COTS high GBP, low-noise op-amps would you recommend for the best 1/f performance? Currently I'm using the LT1028, mainly because I have some left over from an earlier, higher frequency (tho
Theophilus Stark 1. That does not work well as the DSA cannot measure it's own noise and the Input noise at the same time. Using a former reading is very inaccurate. Also the reliability is just low. So as Dave said, use a low noise preamp and everything is fine. This Instrument is not intended for such low noise Levels.2. It is just vague to pull that off from a single Point. You need to narrow the bandwidth more and get more Points then you will see how it is real. Also Dave has drawn the 1/f curve wrong.3. right, however you still have also capacitive coupling. Shielding is only a reduction not a removal of capacitive coupling of external noise. You can improve by using a guard + shielding (triax). You can also shield magnetic fields. In addition you can reduce Impact of magnetic fields to circuit by circuit design/layout.4. If you really wanna get rid off, just improve the circuit. You can also improve the filter and there is in addition the option to use a sharp band rejection filter.5. The LT1028 is the best integrated opamp for low noise if and only IF you have a low source impedance. From what you write I assume you have a high source impedance and then the LT1028 is dead wrong! I can't tell what is best without knowing your source impedance. And you do NOT need high GBP for a lousy 5-40 Hz low frequency signal.In General: You can get your Project right. Just specify what you want (gain / max noise / max. 50 Hz Impact) and then design your project accordingly. If you use other designs you will get something which might not fit to your Needs. Neither physical Limits nor the power grid is blocking this, only Money and time could. I wish you best luck!
I'm not going to spend several hours extra per video to add subtitles for the few people that would make use of it. That could be more time than I spend shooting or editing. For someone else you would have to find someone technically competent that knows the lingo, plus the aussie slang etc. And is it worth spending the money on that for a few people that might use it anyway? Sorry, but I don't think so. Same goes for other languages.
The drawing on the board is incorrect, the noise result is not 316 nV RMS but 48 nV rms and 316 nVpp. The datasheet figures are full noise voltage density not RMS density. Noise current flows out of the opamp not in and causes additional noise voltage on Input resistance on each pin (V- and V+). And some more issues, so be careful...
Dave put the HP signal analyser in V/rtHz and not the option below for rmsV/rtHz too I noticed. Even though he said all the figures on the whiteboard were in RMS.
"Input referred" is actually rather important. Without saying referred you could be saying the op-amp puts that noise on the input signal, instead of the real meaning, which is noise at the output multiplied by the gain in between input and output.
Dear Dave, what about transistor noise? I have opened BC547 datasheet and see Noise Figure in dB. How to match it to Volts? P.S. I think I found the answer. Decibels express ratio between "real" noise of transistor, OA or anyone else to ideal thermal noise of a resistor. Am I right? Anyone answer me please!
Hello! I have a question and I cannot find the answer anywhere in the internet. My professor uses a complicated approach regarding the calculation of an output rms noise in a OpAmp. He says we must calculate the transfer function of the circuit several times applying a voltage noise as a voltage generator at the OpAmp + terminal and applying 2 current generator at + and - terminals. After this we must integrate the squared modulus of the transfer function multiplied by the power spectral density (PSD), which is usually a known quantity. Then we must calculate the result of this integral, but crazy things happen! He starts considering the loop gain, the ideal gain and the real closed loop gain and after making some consideration about that, he finds some bandwidth where the noise is relevant and multiplies it by a pi/2 factor. Do you have an idea about how this is done? And which consideration I have to do about all these gains to find the rms noise? Or any reference (like books) I can look at?
Can't you use the opamp itself to amplify the referred input noise for measurement, at least to the correct order? You alluded to the fact that this is possible in the video, I think it should work for measuring the amp too, shouldn't it?
So, the elephant in the room. What happens to the noise values at DC? I want to build a low noise instrument to measure DC to 10Hz. How do I know the noise value at DC?
When changing the vertical axis, Dave used the non RMS option (with the RMS option being one option lower). On the whiteboard he said it was all RMS like the 316nV result. Is one of these two things a mistake? Someone else said 316nV was the p-p figure. Can anyone else confirm/explain, pls?
Great videos very helpful and informative what op-amp would you recommend for a stereo low THD audio differential amp circuit for converting balanced audio into unbalanced. i need an entry differential amp for a TDA2822 based headphone amp i am building
Shouldn't the noise density translate to something like e=u/sqB, where e=10nV/sqHz, which comes down to u=e*sqB, instead of the rather confusing explanation you gave. (u is noise, B is bandwidth)
What's the oscilloscope volts hrts faze wave with the least resistance to nitrogen triple bond at 14.7 psi in a double tesla coil with tazor tips electric field?
Trying to figure out how nV/RootHz was derived. Seems like it came from spectral energy density maybe? V^2/Hz .. Ok, turns out I was right. Some explanation here: electronics.stackexchange.com/questions/32257/noise-and-what-does-v-%E2%88%9Ahz-actually-mean .
Cool Stuff this time, Dave...! Noise is very complicated stuff, a whole lecture of my EE-studies only covered the noise. What i still do not understand is, why nearly all "HiFi" companies still using crap&cheap carbon film resistors with respect to the noise...;)
Just a wild guess here but could that be for true resistance over frequency? Some resistors may act like inductors or capacitors at certain frequencies...
Im just getting started with this subject. Im confused, how does 10nV*(sqrt(10,000)) equal 318nV Im sure Im missing something in the material....Thanks for any help...awesome videos by the way..love them all
Hey Dave! I don't know if you check comments on old videos but I wanted to mention some things from my experience at work building amplifiers for signals in the 50nV range. Based on Jim Williams' work, I started using steel cans for my testing. I put my little amplifiers into Altoids mint cans with a voltage divider built-in so I can inject a signal and I have no problems with 60Hz (USA) mains frequency showing up in my measurements. A 9v battery and the amp fit nicely, and I can solder directly to the tin for a solid ground. I have found that die cast and aluminum boxes don't work as well as steel mint or and cookie tins. Ferrous material really helps with shielding! I have been able to show a 100nV signal on the DSA at work with no trouble! Also, I use an HP DSA for spot checks but final plots are done with an RME audio interface and Matlab, which easily beats the HP signal-noise specs. Thanks, and keep up the good work!
Two years ago I watched your OpAmps tutorial video as a 2nd year B.Sc. student preparing for his Electronics class exam. Now I'm working on my B.Sc. thesis and again hats off to your great explanation sir!
Hey Dave, I've been sick for the last few days and I think I might have spent about 90% of my waking time watching your videos, please keep them up they're brilliant :)
Excellent post. Many of the terms used in datasheets aren't obvious and I appreciate you taking the time to make some sense of the more obscure ones that I may incorrectly gloss over when selecting components.
Thank you so much for these op-amp tutorials. I have been building circuits using op amps my entire life, and I never had a true ( thorough) understanding of how they work and how to design circuits with them- until now, seeing your videos. Thanks again.
I was thinking of a follow up video that would take into account the gain resistor noise and input current noise as well. But nothing beyond that.
This video is excellent Dave. Don't be fooled by the apparent little interest of the people who don't get it yet. We want the followup :-)
Thanks a lot.
This video couldn't have come at a better time for me Dave! Thanks. FWIW, last year researchers used layered graphene to determine that "1/f noise becomes dominated by the volume noise when the thickness of the films exceeds ∼7 atomic layers (which corresponds to ∼2.5 nm). The 1/f noise is the pure surface phenomenon below this thickness." [arXiv:1211.5155]
Using the division sign for multiplication is the most engineer thing I've ever seen.
thank you for your work, dave. you have truly made me more interesteed
I suggest you to watch the whole EEVblog video saga, after listening to the 527 videos you'll understand him perfectly ;)
I'd love to see the old 741 here. :)
So...,I'm closed at home because of coronavirus in Spain at the order from our goverment. But, with gems to learn like your videos, i hope not to be bored much next two weeks. Thanks for this videos Dave!.
Great old video Dave, after watching one of your videos years ago about the HP DSA I was able to find one at some government auction, GLAD I did ! Wish you would do some more vids using these ol boat anchors.
These videos make the subject much easier to understand by combining theory with experiments. Thank you !
I am surprised because Dave produces a very clear audio. I recommend to use headphones. It helps me sometimes. Not that I ever needed them on one of the EEVBlogs.
Loved how you dropped in the 5534 in the end. Millions of those and millions of TLO72/3/4 in audio products over the decades.
Great video. You answered so many questions I had about my HP3562A analyzer. I would love to see you make video about dropping in the high performance modern lower noise parts in it. And then see you go through calibration. It would be a great video mate!
I used to have an Ono Sokki. Don't recall the exact model though, but it wasn't that one, much older.
I'd like to see that opamp upgrade video.
Speaking as a physicist (to be, at least), I have the urge to add another clarification to the video. Namely: physics ALWAYS makes sense - it is, however, sometimes counterintuitive. There's a huge difference. Great video though, thanks Dave
Love fundamental Fridays, I always learn something new. The subjects are practical and your explanations are always very understandable. Thanks!
Thanks a lot....we're learning this in our masters and your explanation is better!!
It generally takes well under an hour. I can literally watch the counter increment on every page refresh. And it usually takes less than a minute after release for someone to comment!
Even though I don't suppose I'll ever use this information, I find it highly interesting. You have quite a nice way of explaining things.
Speaking of noise, perhaps an upcoming video could explain the different types of noise you mentioned at 13:00. Something of a comparison of each type, how they are generated, and how different components (resistor vs. cap vs. inductor vs. transistor etc.) are affected by the different noise profiles. Maybe even techniques to deal with the different types.
Good video. I love the fundamentals videos. Please don't stop doing them, there's not enough educational content on the you toobs.
The video is already uploaded, but it's just me taking the lid off and looking at the devices.
Another superb video. I can't wait for the 35660A upgrade video.
Really nice video and good old intrument there.. One thing you could have shown was the effect of the cable+box without any opamp active. That could give better base level for testing the opamps instead of direct 50ohms termnation.
Very informative indeed. I've learnt a few things. Thanks.
Excellent refresher. Thanks Dave.
Thanks Dave. I learned a lot. Another great video.
You are our favorite teacher!
Actually it possible to measure the noise of an op amp with only 10nv/rtHz if your op-amp have some gain. For example, if your op-amp have a gain of 10, at the ouput, the noise will be arroud 100nv/rtHz ! Because this is the noise defined to the input of the op-amp and it will be amplified by the op-amp.
I'm really looking forward to see the "optimizing the 35660A with modern input opamps"-video! I hope i''m not alone! =) btw... i really liked the whole tutorial, it gave me much new knowledge about op's! Thank you!
That was such a fun vid! I learned a lot, and I loved that you used the DSA we had fun watching you troubleshoot and repair. You'd make a fun character if there was ever going to be another Mad Max film (one of my favorite movie franchises, btw).
Would like that. Some practical real world advice for low noise audio. Where using a metal film resistor makes a difference and why, etc.
Loved the video ! Thank you for this.
Excellent. Clarified many questions on Op Amp noise.
Thanks.
There are many sources to consider if you want to do this properly, I just wanted to do a quick test to see if I could show the difference between opamps. This is ballpark stuff.
nice to see you using lab instruments like the DSA
I would never take it to the bank! I recon I make some sort of mistake or slip of the tounge in most videos. I did in this one, hence a few annotations. The off-the-cuff nature and the difficultly of checking ones own work during editing means mistakes will always slip through.
Awesome video Dave. Great timing too, as I was reading up on this earlier!
The reason I love this channel, is that you can take everything that comes out of Dave's mouth to the bank. Too many people try to bullshit their way through a video like this. Great video!
The answer is correct.
Excellent tutorial.
You're the best. Hats down Dave, really.
Great video Dave.
Do you mean inverting and non-inverting configurations? If so, the answer is no, it's the same. You don't use positive feedback for amplifiers.
I was hoping you would show the difference with the lid off the box.
Thanks
In case anyone else goes looking, the component Dave used at the end is the NE5534, not "NA5534". I have a hard time distinguishing his As from his Es. I first heard Dave on the AMP Hour podcast, and for quite some time I thought he wrote the AAV Blog.
But you could probably use "any 5534" :-)
Superb video Dave - I learned something new about op-amps.
Try the automatic subtitling (right lower corner of videoplayer frame). Works!
Very good explanation! It was a good help ;). I need to amplify the output voltage of a 1kHz notch filter, uVs... to measure a SINAD in an audio Amplifier. But I'm having troubles with the noise. Now I'll try reduce the resistors values and chose an op-amp with a reduced noise, now the ne5532... Many thanks! My Channel is in Portuguese sorry... Regards, Hugo.
Excellent presentation!
I do have a couple of questions, however (warning: long post): why doesn't the DSA use its own calibration data to remove its average noise contribution from the display? Much like 'taring' a scale? The math is straightforward enough as demonstrated by your own calculations at the cursor frequency and SO shouldn't be all that taxing to the analyser's CPU, so why doesn't the DSA do that for you at all the points? That would be very convenient, yes?
My second question is: why does the displayed 1/f frequency curve taper-off at the lowest frequencies instead of increasing with decreasing frequency as all 1/f curves do? Surely this is an artifact? Even with _two_ data points it should sweep much higher than seen on this video (as at f = 0 Hz it is theoretically _infinite_ [but would take an infinite time to measure] :). Is the DSA bandwidth-limited at that end even with DC coupling, and even though it is spec'd from _DC_ to ~100 kHz?
And just a note: coax shields are generally pretty good as _electrostatic_ shields, but not so great where _near field inductive_ coupling is concerned, where there's a measurable AC _magnetic_ field gradient penetrating the shield into the space between shield and the centre conductor? Same for die-cast aluminium boxes. Possibly a good mu-metal enclosure (at least for the DUT and wiring), may reduce that 50 Hz peak somewhat? Give it a try and see if it makes a difference.
Mains frequencies (and harmonics) are the bane of my applications, VLF/ULF/ELF radio receivers. The one I'm designing at the moment has a passband beginning well inside that 1/f curve, with the upper stopband beginning at around 40 Hz. Even so, 50 & 60 Hz mains frequencies can be strong enough to swamp the preamp and it is nearly impossible, it seems, to get away from it - short of moving to _Antarctica._ :(
As far as 1/f specs go, in your experience which COTS high GBP, low-noise op-amps would you recommend for the best 1/f performance? Currently I'm using the LT1028, mainly because I have some left over from an earlier, higher frequency (tho
Theophilus Stark 1. That does not work well as the DSA cannot measure it's own noise and the Input noise at the same time. Using a former reading is very inaccurate. Also the reliability is just low. So as Dave said, use a low noise preamp and everything is fine. This Instrument is not intended for such low noise Levels.2. It is just vague to pull that off from a single Point. You need to narrow the bandwidth more and get more Points then you will see how it is real. Also Dave has drawn the 1/f curve wrong.3. right, however you still have also capacitive coupling. Shielding is only a reduction not a removal of capacitive coupling of external noise. You can improve by using a guard + shielding (triax). You can also shield magnetic fields. In addition you can reduce Impact of magnetic fields to circuit by circuit design/layout.4. If you really wanna get rid off, just improve the circuit. You can also improve the filter and there is in addition the option to use a sharp band rejection filter.5. The LT1028 is the best integrated opamp for low noise if and only IF you have a low source impedance. From what you write I assume you have a high source impedance and then the LT1028 is dead wrong! I can't tell what is best without knowing your source impedance. And you do NOT need high GBP for a lousy 5-40 Hz low frequency signal.In General: You can get your Project right. Just specify what you want (gain / max noise / max. 50 Hz Impact) and then design your project accordingly. If you use other designs you will get something which might not fit to your Needs. Neither physical Limits nor the power grid is blocking this, only Money and time could. I wish you best luck!
I'm not going to spend several hours extra per video to add subtitles for the few people that would make use of it. That could be more time than I spend shooting or editing. For someone else you would have to find someone technically competent that knows the lingo, plus the aussie slang etc. And is it worth spending the money on that for a few people that might use it anyway? Sorry, but I don't think so. Same goes for other languages.
The drawing on the board is incorrect, the noise result is not 316 nV RMS but 48 nV rms and 316 nVpp. The datasheet figures are full noise voltage density not RMS density. Noise current flows out of the opamp not in and causes additional noise voltage on Input resistance on each pin (V- and V+). And some more issues, so be careful...
Dave put the HP signal analyser in V/rtHz and not the option below for rmsV/rtHz too I noticed. Even though he said all the figures on the whiteboard were in RMS.
2 mins in and I'm completely lost.
Sounds like a really good video though ;)
More Fundamentals like this! Less Fundamental, more intermediate.
Great video, thanks Dave
"Input referred" is actually rather important. Without saying referred you could be saying the op-amp puts that noise on the input signal, instead of the real meaning, which is noise at the output multiplied by the gain in between input and output.
Are you sure that the dsa is calibrated?
In feature you'll do a teardown of the unit or pheraps, if needed, a calibration of the unit?
Brilliant video Dave.Thx a lot
The thought never crossed my mind! :->
Love your videos. Very helpful
Agreed, still waiting for the FPGA tutorial..Thumbs up anyway Thanks.
Fantastic episode as usual Dave. Thanks! :)
How do you reduce it? I have a noisy SE1000A Mic producing allot of white noise Hummm. Any ideas? Can I install a trim pott to balance the rails?]
Nearly to the 301+ threshold in under an hour. You're pretty popular Dave!
Dear Dave, what about transistor noise? I have opened BC547 datasheet and see Noise Figure in dB. How to match it to Volts? P.S. I think I found the answer. Decibels express ratio between "real" noise of transistor, OA or anyone else to ideal thermal noise of a resistor. Am I right? Anyone answer me please!
god damnit Dave its 4:35am here and you always have to upload a video to keep me awake until the sun rises
Can we say that nV/sqrt(Hz) is basically the power spectral density. If we sqr() this we get W/Hz over 1ohm resistor.
that signal analyzer what a beaty!
Why don't we use 100Mohm resistors on our Opamp voltage dividers? I always see things like 47kohm.
Hello! I have a question and I cannot find the answer anywhere in the internet. My professor uses a complicated approach regarding the calculation of an output rms noise in a OpAmp. He says we must calculate the transfer function of the circuit several times applying a voltage noise as a voltage generator at the OpAmp + terminal and applying 2 current generator at + and - terminals. After this we must integrate the squared modulus of the transfer function multiplied by the power spectral density (PSD), which is usually a known quantity. Then we must calculate the result of this integral, but crazy things happen! He starts considering the loop gain, the ideal gain and the real closed loop gain and after making some consideration about that, he finds some bandwidth where the noise is relevant and multiplies it by a pi/2 factor. Do you have an idea about how this is done? And which consideration I have to do about all these gains to find the rms noise? Or any reference (like books) I can look at?
Why is input noise divide by the gain rather than multiplied?
The more I learn about precision electronics, the less I am able to sleep at night after completing a project.
It wouldn't be huge, you are still stuck with the small dynamic range.
Why is the 50Hz noise if it is totally shielded?
Can't you use the opamp itself to amplify the referred input noise for measurement, at least to the correct order? You alluded to the fact that this is possible in the video, I think it should work for measuring the amp too, shouldn't it?
So, the elephant in the room. What happens to the noise values at DC? I want to build a low noise instrument to measure DC to 10Hz. How do I know the noise value at DC?
When changing the vertical axis, Dave used the non RMS option (with the RMS option being one option lower).
On the whiteboard he said it was all RMS like the 316nV result.
Is one of these two things a mistake? Someone else said 316nV was the p-p figure. Can anyone else confirm/explain, pls?
Great videos very helpful and informative
what op-amp would you recommend for a stereo low THD audio differential amp circuit for converting balanced audio into unbalanced. i need an entry differential amp for a TDA2822 based headphone amp i am building
Is the current input noise related to the voltage input noise?
Muy buen vídeo, saludos desde Colombia!!!
Uncle Bob would put in screws to lock the box. 😎
Thanks, man! It was great
Interesting!
Shouldn't the noise density translate to something like e=u/sqB, where e=10nV/sqHz, which comes down to u=e*sqB, instead of the rather confusing explanation you gave. (u is noise, B is bandwidth)
So it's better to use AC if you wanna amplify the microvolts from a thermocouple?
+bergweg No you need opamp to do sense circuit. It copies the dc and outpus 0-X Volts range.
Nice job!
What's the oscilloscope volts hrts faze wave with the least resistance to nitrogen triple bond at 14.7 psi in a double tesla coil with tazor tips electric field?
Trying to figure out how nV/RootHz was derived. Seems like it came from spectral energy density maybe? V^2/Hz ..
Ok, turns out I was right. Some explanation here: electronics.stackexchange.com/questions/32257/noise-and-what-does-v-%E2%88%9Ahz-actually-mean .
Now I think I see why the DSA had all that shielding.
Cool Stuff this time, Dave...!
Noise is very complicated stuff, a whole lecture of my EE-studies only covered the noise.
What i still do not understand is, why nearly all "HiFi" companies still using crap&cheap carbon film resistors with respect to the noise...;)
Just a wild guess here but could that be for true resistance over frequency? Some resistors may act like inductors or capacitors at certain frequencies...
Sorry, but they are incredibly time intensive to produce, or very expensive to have someone do for me.
nice tutorial, but where are fpga tutorials?? :)
50Hz pick up is usually from the AC mains !
And 100hz. 60 and 120 if you are in the US. 100/120 hz hum is nearly always due to leaky capacitors across the bridge rectifier.
Dave, make another power supply video :)
great vid. thanks
Im just getting started with this subject. Im confused, how does 10nV*(sqrt(10,000)) equal 318nV
Im sure Im missing something in the material....Thanks for any help...awesome videos by the way..love them all
1,000Hz, not 10,000 Hz