My 'Video Response' to Dave's Op-Amp Video  +  other recent projects - Page 1
Forum section: electronics / projects

author: Post_Apocalyptic_Inventor
author_rank: Contributor
timestamp: April 07, 2014, 09:38:25 pm
content: Hey there!I watched Dave's tutorial video about op-amps yesterday. I spontaneously got the idea to make an additional tutorial video about op-amps myself. I think of it as a 'video response' to Dave's tutorial. Since Youtube's 'video response function' isn't available anymore, I though that I would just post it on the forum.My video is not repeating the content of Dave's video. I simply thought that I could cover what Dave simply couldn't be bothered to talk about: Some mathematical background for the stuff he explained in his video. Since he started with the inverting amplifier and made a pretty good job in explaining its working principle, I now made a video of how the amplification factor ( or better yet „the transfer function“ ) of the inverting amplifier can be derived mathematically.The method I demonstrate in the video though can be used for an unlimited amount of different op-amp circuits other than the inverting amplifier as well. Therefore it is quiet a useful tool to have.Since I'm already posting this video, I might as well show You some of my other recent videos:Therefore You find 4 links for totally different videos in this post.1.) My first tutorial video about op-amps "Transfer Functions"2.) Part one of my tutorial-series on Switched Mode Power Supplies3.) A video about how I generate electrical energy with my exercise bike.4.) A just for fun video of me cleaning my „Horror Basement“(My advice: If you don't like the „theoretical style“ of the op-amp-video, then try some of the others, they are different in style)

author: 128er
author_rank: Regular Contributor
timestamp: April 07, 2014, 10:20:10 pm
content: What should i say? GroßartigI think its a good addition to Daves video. Also for people without big mathematical knowledge (Me), it is comprehensible. I like your calm style!I will have to look it more than one time, search for examples in circuit diagrams and do some calculations for my own.Thanks for your work!

author: EEVblog
author_rank: Unknown
timestamp: April 07, 2014, 10:35:39 pm
content: Quote from: Post_Apocalyptic_Inventor on April 07, 2014, 09:38:25 pmYeah, what's up with that, stupid.I knew they gave the stats for how many people actually use it (or don't use it), but what does it cost to keep it in place?

author: EEVblog
author_rank: Unknown
timestamp: April 07, 2014, 10:37:30 pm
content: Great work on the video, very nice.

author: Post_Apocalyptic_Inventor
author_rank: Contributor
timestamp: April 08, 2014, 04:38:43 am
content: Thank You very muchNice to know You guys like it !About the "video responses": When I read about the cancellation of the video response function by Youtube some month ago I was very disappointed. I was planning on responding to several videos of different people back then and I never understood what made Youtube do that. It's stupid. But then again it fits perfectly in the long series of bad decisions, which are sold as "improvements" to the Youtube users.To "128er": I like to hear that it is easily understood. I'll try to upload part 2 as fast as possible. It will help to see how the method works. Other than that: it's just a matter of "training". When I tried to calculate such a function for the first time, it took me a long time too.

author: Zad
author_rank: Super Contributor
timestamp: April 08, 2014, 05:24:27 am
content: Quote from: EEVblog on April 07, 2014, 10:35:39 pmIt was abused, mostly by teenage girls in very low-cut tops after the click-through revenue, albeit with genuine sounding titles, and other generic spam. Some of the bigger YouTube publishers (gaming related channels often publish several a day, getting hundreds of thousands of views) were just getting hundreds of these video responses clogging their pages. To get them banned required a tortuous complaint process, and people able to monitor your channels for spam 24 hours a day. In truth, this was where the problem lay, and as we know, YouTube would rather do anything than have an efficient, open and transparent complaints system!

author: Post_Apocalyptic_Inventor
author_rank: Contributor
timestamp: April 08, 2014, 10:25:57 am
content: Yeah, it sounds reasonable that video responses would have been abused by some people to profit from the popularity of others. I can only imagine how annoying it must have been for the people who run those major channels to file all those complaints. But then again, I don't know if Youtube as a company really cared about that...I just have the impression that the people who manage Youtube are masters of 'improving things for the worse".

author: dannyf
author_rank: Super Contributor
timestamp: April 08, 2014, 10:45:34 am
content: QuoteThanks for that. Maybe in the future you can talk about opamp noise - some "engineers" could benefit from that.

author: TMM
author_rank: Frequent Contributor
timestamp: April 08, 2014, 12:07:20 pm
content: Quote from: EEVblog on April 07, 2014, 10:35:39 pmProbably the jobs of the people who gather such statistics and make (pointless/stupid) changes to the site to justify their existance

author: EEVblog
author_rank: Unknown
timestamp: April 08, 2014, 12:21:19 pm
content: Quote from: Zad on April 08, 2014, 05:24:27 amBut there was always the option to have to approve video responses before they went on your page, so this would have only been the case if you were dumb enough to auto-approve them.

author: EEVblog
author_rank: Unknown
timestamp: April 08, 2014, 12:22:12 pm
content: Quote from: dannyf on April 08, 2014, 10:45:34 amI've done that:

author: GK
author_rank: Super Contributor
timestamp: April 08, 2014, 12:52:29 pm
content: Quote from: EEVblog on April 08, 2014, 12:22:12 pmYou don't need a DSA with a particularly low noise floor to measure even the lowest noise op-amps. Instead of configuring the op-amp as a unity gain follower, you can configure it with gain with the non-inverting input grounded, such that the op-amp is just amplifying it own input voltage noise to a level comfortably above the analyzers noise floor. The measured result is divided by the gain to arrive at the actual input noise. You just have to scale the feedback resistors such that their own noise contribution is negligible in comparison to the op-amps input noise. Fortunately low value feedback resistances can be used here because the output of the op-amp wont be driving them to any significant levels.The only thing to be aware of is the limitation of gain bandwidth product. For example, if you are measuring a 3MHz op-amp and have configured the closed loop gain Av=100, the closed loop bandwidth will drop to 30kHz, and that will cause the measured noise to start rolling off even before the top of the audio frequency spectrum.

author: Post_Apocalyptic_Inventor
author_rank: Contributor
timestamp: April 08, 2014, 08:04:28 pm
content: Well if you haven't got super sensitive equipment at hand that would be a reasonable method to measure the op amp noise. You would however need resistors with somewhat precise resistive values so that you could be certain about the value of voltage amplification. But that of course is still much easier to obtain than some expensive DSA...But other than that: Do you guys have some old score to settle, that I don't know about ?

author: GK
author_rank: Super Contributor
timestamp: April 08, 2014, 11:34:40 pm
content: I just use 1% resistors and scale the values so that the resistance presented is one tenth the equivalent noise resistance of the DUT, which gives accurate enough results for me.