#1177

[@RexxSchneider]

If you re-check the "Voltage Follower Pulse Response" for the LM324 (at 9:06 ), you noted that it swung around 2.5V in 5μs, so you could have worked out that its slew rate is 0.5V/μs. That's pretty standard for these old op amps. It means the TLC274 is around 10 times faster.

[@fredmitchel1236]

Yup love the LM324 predictable nice and slow...used in AGC ...nice analog build performance..no balance 0.5 V per uS tops?...I guessed...then looked it up...good to see a match and my memory not all lost.. Malvino - my old primary electronics text among some others at Gateway Community -there were his handy formulas...maybe all one needed was some algebra... Fmax=Sr/2piVp... Like power bandwith of an op amp..before distortion .. So the LM324...if we wanted or needed 20 Vp-p.... Then max frequently ....slew rate limited would be less than 8 kHZ... Another great lesson Imsai guy...devils in the details and nice contrast between slower and faster chip... I will look up IMSAI Guy esposide when you reviewed books... He was that desigher of how to make something that worked and was his designs were the most part stable...i can see his face and remembered his messy work bench...he once worked at LT.. Smarter than a John Titus. I like the MASAI Guy for you summarize well cut to the chaise without long math proof have lots of nice WORKING test equipment to demo verify your predictions and show proof...and if it arrives in need of repair...that gets done too.. I can see how you can be on teams obtaining the +60 patients that was like a byproduct of your job... One of our bought out and acquired company morphed into something large...but yet broken within- everyone tried -so did I.....we had folks who thought of all day of more to patent ...There was $$ incentive too for patent granted. Not all or by far were some such patents ever used or implemented but were certainly new...IBM had a nice sort of balanced program...that is a token amount for your idea...it was appreciated...and if that item was used in production then you get a tiny cut more... Once upon seeing our competitors product...managed and funded with money were & were organized used and could apply it ...I saw it...& was amazed... the writing was on the wall - and was wrote in my mind. They executed...and blew us out of the water....I think the writing or their design launched in 1993....I think our last gasp came in 2007 then dissolved.... Also new management came from electronics....but were not necessarily good at building machinery... For instance some came from Tektronics...who did well there...created a fifth arroew..but not necessary well as a leader in that machinery sector. Couple that with yes men... No doubt smart. Howdy Rick Hill. How come I was never invited to Maui? Lol...its all good. One of my favorite magazines 1975 say to 1990.?...was EDN....esp. the section where readers submitted their novel circuits...and they show a little application usually using the newer chip available I looked in World Radiio or I am looking for EDN archives....X wife tossed out lots...and I wasn't there to stop her... Most of my Nuts and Volts avoided the round file....it is hard to part to with them. I have been whittling down the pile. Fred you said you wouldn't babble

[@copernicofelinis]

One thing I have noticed is that the fake op amps, that are a kind of Chinese 358 or 324, are faster that the actual 358 - 324. I got on average 1.8 - 2.2 V per us.

[@TerryClarkAccordioncrazy]

The 324 is great so long as you're not working in the 100s of kilohertz. Used it in inverter and PSU designs, no issue

[@Edisson.]

How simple and instructive, one example will say more than a thousand words. 👍 I encountered this problem when I was making a TDR, the prototype worked at a frequency of about 6kHz, the final product built into a large BNC connector 2.8 kHz same voltage, values and types of components just another IC of the same type. It works the same, the shape of the curve is the same, only the frequency has changed, the tolerances of the components are responsible for something, but I tried to choose the same values. Nice day 🙂 Tom

[@andymouse]

I'm glad I found you as your always clear, concise and easy to digest !...cheers.

[@stamasd8500]

2.5V per 5us is 0.5V/us; that's about 10 times slower than around 5V/us for the TLC274.

[@t1d100]

I love chip-of-the-day. Thank you. Great explanation of the 324's slew rate problems. As others point out, this chip is h-i-g-h-l-y faked. If it is what you want, only buy it from a known OEM distributor.

[@chriswalford4161]

👍🏻👍🏻

[@SS-mj2mq]

Or stripping from a really old audio board or mixer if you can find one 😂 And of course I'm sure you can find them in other things they were widely used but very popular for audio use.

[@pauldougherty8049]

I think you misspoke at 7:05 or so. You say "slew rate of the oscilloscope" when you meant slew rate of the opamp. It's right after the touchscreen oscilloscope woke up, drawing attention to itself.

[@d614gakadoug9]

ANY op amp can be used with a single supply or dual supplies. The questions are how close to the supply rails the output can swing and what the input common mode voltage range is. Op amps generally are slow when used as comparators. Two things come into play. Saturation of the output transistors, which are relatively large, means it takes time for excess carries in their bases to be removed or recombine so that turn-off can start. The other thing is that when the amp is driven to "large signal" operation, as they are when used as comparators, the internal frequency compensation capacitor(s) accumulate charge they would not in small signal operation. That excess charge needs to be removed to get signals to move. Amps without internal frequency compensation are generally faster but they are something of a rarity these days. If you want a good comparator, use a device intended to be a comparator. One advantage to an op amp as a comparator is that you can select an amp with ultra-low input offset voltage, such as a chopper-stabilized or "commutating auto-zero" amp. There are also a lot more choices if you need really low input bias current.

[@brianharper9798]

Am I right, looking at the circuit there, if you vary the voltage on the inverting input of the last op amp you shoult be able to vary the pulse width of your square wave.

[@RexxSchneider]

Well, it's really the duty cycle you would vary as the sum of the high pulse width and low pulse width is bound to stay constant.

[@colonelbarker]

Oddly enough Element 14 posted a video about Op Amps covering slew rate about the same time. As others have said, your chip of the day videos are amazing. Any chance you could cover some pic16s at some stage? Info on KZbin is a bit scarse. Well, clear and to the point.

[@davidsotomayor8713]

Very low slew rate op amps are actually sought after for guitar overdrive/distortion pedals. You get a nice natural roll off of the higher frequencies.

[@johnb7805]

Thanks for the video! But could you please go into more detail by what you mean by stiffen the 6 volts. How do calculate the return path current? Coming off of your 12 volt divider why use the op-amp follower and not just come off of the top of the resistor for the 6 volts? If you have the time, could you go into more detail, that would be great! If not, we'll still thanks for the video! John

[@IMSAIGuy]

most of the time you don't need a buffer on the 6V, a nice capacitor is good to lower the noise. I just wanted to show one as many circuits have current that returns to ground, or in this case it returns to 6V and so if you have 100mA of return then yes you need a buffer

[@RexxSchneider]

In detail, using 10K + 10K as a resistive divider to generate a 6V rail from a 12V rail is equivalent to a 6V supply with an internal resistance of 5K (the parallel combination of 10K and 10K). So if you tried to draw 1mA, for example, from that 6V rail, its voltage would drop by 5k * 1mA = 5V. That really isn't going to work if the +6V rail is now at just +1V. However, if you buffer that resistive divider by using an opamp as a non-inverting amp with a gain of 1 (i.e. a "voltage follower") as shown in the video, then you can probably draw 50mA or more without any significant change in the 6V output.

[@michaelmolter8828]

Just used a LM324 because I needed the large voltage range for a +\- 12 VAC output. Modern op amps don’t have that kind of voltage range. For everything else non-demanding I use the LM”V”324 or the MCP6002.

[@michaelmolter8828]

Yikes. Didn’t notice it was that bad! Your at roughly 6.5 kHz, so I’m probably okay in my application at 500-1,500 Hz.

[@W1RMD]

Excellent info! Great channel you've got here. 73's!

[@AlessandroAllegretti]

Thank you very much! I've tried slew rate tests for single opamps, but I was unsure that I was using the right setup for. I'll retry it with your schematic. Just a question: is it true that some opamps are designed exclusively as comparators? Can you explain the differences among opamp and this exclusive comparator in a next video of your? P. S. Nice those radios on your bench! 😊 73 de IU8PWV 👋

[@IMSAIGuy]

kzbin.info/www/bejne/o5-1gGSFgJuVp7s

[@SS-mj2mq]

@@IMSAIGuy The fender Rumble 15 bass amplifier has a really nice circuit diagram that is also compatible with this IC LM324. And you can also use a TLO74 or a TLO84 pinouts are compatible 😁💯 💖 Please considering checking it out online you can download the schematic and share it! 😊 The schematic is more than 10 years old so you can not get in trouble for using it in a tutorial. So you could build it and share it if you wanted to. I think you will be impressed with the quality sound that it will produce. I plan to use it in one of my amplifier builds as the main preamp. I called fender tech engineers and they told me I could do whatever I want with it lol they've made their money. JBL and Peavey have also told me the same thing. I have given them quite a bit of business so i have got in good with them had long conversations on the phone with some and made friends. Wonderful people to work with👍💖💯 LOL they've actually sent me free stuff such as parts and components on the house. They are allowed to do that if they want. There motto is keep the customer happy and they'll come back and word of mouth is everything. And they love it when you fix their products because it makes them look good as a professional audio amplifier distributor or maker. So they don't mind helping you get the job done. Back to the schematic that I was talking about one thing I definitely like about the schematic is they used two zener diodes D1 and D2 on the input and you add +12 and negative 12 volts to them it keeps you from overloading the op amp input additional protection against both high voltage and negative voltage in a single component!👍👍 And note you can use this preamp in any amplifier design you want and you don't have to use the TDA chip amplifier or the LM chip or the JFET that is in the schematic if you don't want to. 👍 I know I was all over the place but I had a lot on my mind to share😁

[@AlessandroAllegretti]

@@IMSAIGuy Ooohh, many many thanks, Sir! That is what I was looking for!❤️👍

[@RexxSchneider]

You usually test slew rate with the opamp configured as a non-inverting buffer with something like a few tens of pF as a load.

[@SS-mj2mq]

Yes some op-amps are specially designed just for sound reinforcement of course for amplifiers! That's why you pay more for those op-amps. Some op-amps do not have quality sound because they are used for like in computers to run certain functions on the motherboard or maybe in a TV or maybe you know in a car computer or to run machines or even used in a microcontrollers to link the analog world or even for a power supply. So they purposely do not make all op-amps super clean because there's no need for it It's just used to control things or as a controller. That's why it's important to look at the data sheet to see what the op-amp is designed for and for it's general purpose and what it is best suited for in a application. But not to say that I have not seen high quality op amps designed for sound reinforcement in a power supply or in a TV or even in a microcontroller and more. Because they do sometimes use them. Yes I know my comment seems a little redundant 🤭 And the jrc-4558d op amp is very universal and popular too. You can use two together to build a quad op amp. Just thought I'd throw that out there. There's a lot of other factors but this is a few examples of the difference between op amps. I hope this will help you and have a great day 🤗

[@francescobattaglia5322]

Wow!! great explanation!

[@Enigma758]

Do you think it would be a "bad" design to build a circuit that takes advantage of a low slew rate part such as the LM324? For example, if your goal is to build a sine wave generator and you use the LM324, then you could get away with less filtering (and possibly reduce a stage, thus simplifying your circuit).

[@andye2005]

Bad - Your design would then become less reproducible - slew rates vary quite a a bit

[@copernicofelinis]

One advantage of slow Op Amps is that they tend to be more stable than their faster counterparts. Sometimes too high a SR can be detrimental.

[@Enigma758]

@@andye2005 Good point, thanks for your comment!

[@marka1986]

Look up the circuit for the lm324 esr meter. This is an excellent example of getting the most out of a low bandwidth op amp.

[@Enigma758]

@@marka1986 Thanks, I found the schematic, but from looking just looking at it, it's hard to know what the bandwidth implications are.

[@aduedc]

Here are general purpose opamps that I like TL071H, TL072H, and TL074H. You guys know other general purpose opamps, please share. Also, if you guys know of very fast opamp, at reasonable price range in the market, please share.

[@RexxSchneider]

TI make a range of video amplifier opamps which will probably be the fastest cheap opamps. Mouser prices the SN10501 (100-MHz bandwidth, 900-V/µs slew rate) at £1. For a fast general purpose opamp. I've used LM318 for many years. It's a bit old in design these days, but still performs well.

[@aduedc]

@@RexxSchneider Thanks I will check it out.

[@Batmule]

Good content. Thanks!

[@kabandajamir9844]

So nice

[@michaelschwager786]

Thanks, imsai guy! I always learn a lot from your videos.

[@bobdoritique7347]

Merci.