 The great church doctor by did you key nature fruit? Thank you so much. Did you key every single lady to use their powers? For good to help you find things on the did you key site? And that's happening a lot because people are starting to notice there's no chips. That's right We have a chip shorts going on so here's two tweets. These are tweets from some synth folks Who are talking about how there are shortages of chips, and it's true the sami 21? There's there's delays on it, but also I noticed two people were chatting about how the TL o 74 was not available I was like wow, that's pretty amazing TL o 74 is a it's a classic chip, and I'm it's used a lot by synthesizer folks, and that's actually kind of wondering why so I checked in With guest who was the co-designer of the zoxox synthesizer that we worked on I said like you you know op amps and synthesizers what what's so great about the TL o 74 And I do want to I want to say it because it's actually kind of neat and it will also help us in the great search What we're gonna look got so guest says the o 74 is pretty much the Toyota curl of op amps It's not the best at anything in particular, but pretty good at everything It's the second cheapest op amp out there comes in dip and so I see it has relatively low current consumption Low distortion and reasonable bandwidth and slew rate the noise is okay It's low, but the thing that really makes it all outperformer is the low bias current j-fit inputs j-fit inputs It's down in the pico amp range, which means you can use it for a sample and holds or vco's vcs They require range of currents down to the nano amp ears a lot of people use the LM 358 because it is the cheapest op amp, but it has high bias current the o 74 can also handle high voltage rails Which helps for the signal noise ratio It was designed for audio use and was the first one of the first real mass market op amps back in the late 70s If I recall correctly the 741 was the first still people use the 741 way popular op amp And this was meant as an improvement over that the o 74 and the o 8 4 Were made at the same time in the o 74s were selected for no lower noise third distortion and lower offset voltage and then marketed at the audio market the o 84 was sold to everyone else so This is a good hint again, you know, there's op amps are very very peculiar You know once you find the specs for one it's hard to say like this is an absolute alternative, right? There's no There's it's not easy to say like this is it other than the exact part number Each one has slightly different specifications and there's so many specifications So I will say that I don't guarantee this is going to be a drop in a placement for the TL o 74 but for synthesizer uses it sounds like the JFET inputs in the low bias input current and Pretty good slew rate and Pretty good Voltage range so you may be more than five volts like they you know plus or minus 12 volts It's pretty common for many synthesizers. So let's go to digiki and let's actually look up the TL o 74 I will say the TL o 74 is is there are some in stock like you're not totally Out of luck if you want some It may not be available in every You know particular flavor and package size, but there are some in stock. So it's not it's not the end of the world You can get some But let's look at some of the specifications that guest mentioned So the slew rate is 13 volts per microsecond three megahertz gain band with product input bias current 64 pico amperes input offset 3 millivolts About a milliamp and a half per channel of supply and then yeah plus or minus five volts Or 10 volts to 30 volts that is something interesting. So you do need to have a fairly high voltage It looks like you can't really looks like there might be versions like here the TL o 74 HIDR There are some that can run as low as 4.5 volts single supply, but it looks like 10 volts is pretty common So that said let's take a look at Similar op amps has got the JFET input. That's what kind of defines the the low input bias Let's look for another quad low input bias op-amp that could be an alternative to the TL o 74 So let's go back to buffer amps and Let's look for active and let's look for in stock because we're we're we're on a we're not specking up a New board here what we're doing is trying to find an alternative to a part that we know in love I'm not related to it. Yeah, I guess for whatever reason like a hundred plus people showed up in twitch Okay, hi, and so they thought it wasn't live and now they're being taught how to search and use electronics Yes, I don't think that was their intention who doesn't love synthesizers I think this is some type of raid or something But you're just gonna learn you're just gonna learn stuff and you're gonna learn about mechanical keyboards and how to specify op amps for synthesizer You know statistically 3% of them make synthesizer do music you wonder like how is how are this come back every Sunday and learn some Electronics folks. Okay. Okay. There's no we're not doing any hot tubs here, though Okay, so we want a quad op-amp because we're gonna go 74 that four stands for quad 72 is dual, but we want quad So let's let's apply Okay Next up I don't really care about the current for channel But again, I do care about the input bias in this case. I'm going to use this min max box Well, hold on Hey, we're gonna use the min max box. There's actually a little bit of different styling by the way I think they updated the search styling the CSS updated So let's look that remember the l 74 was 65 Pico Ampere's let's let's put in like I don't know like 80 right up to from 0 to 80 Pico amps Okay, great. So we've got a whole bunch of those and let's look at Slew rate. So we want a pretty good slew rate and some of these are like pretty Slow like, you know less than a volt per microsecond. I think what was the 75? It was like 13 or something let's Let's find something that's at least five. Oh five volts from millisecond. We want for a microsecond So let's do five volts or greater per Microsecond and watch out because it looks like the milliseconds are mixed in with the microseconds Okay, great So looking good. I've got about 400 options. Okay Next let's look at the we want surface mount so let's let's pick that and I'll cut us down to 300 pieces Okay, so what else do we want to do? So the input offset? Let me look again at what the input offset was for the TL 070 whoops 73 one thing that's nice by the way about op amps is that op amps do have Almost all op amps have the exact same pinout like thankfully So if you have a quad op amp that's in a 14 T sop It's gonna be the same as every other op amp in a 14 T sops. You don't have to worry about like You know, it's like it's like what we talked about in some previous Tutorials about you know, oh this reset actuator uses like a slightly different pinout depending on the package It doesn't that doesn't fly here Okay, so the TL 74 So we're looking at the slew rate 13 volts for microsecond gain bed with project of three megahertz Really good input offset about three millivolts. So let's do three millivolts or less This is in microvolts So it looks like you know, there's There's actually like the input offset isn't too bad. There's only like one that's like half a volt ridiculous Okay, um So let's take a look at what's available. So one thing about the TL of 74 is of course, it's really cheap So let's let's sort by price let's put in price at 1,000 and Sort by price, okay So not surprisingly the TL 84 comes up first So, you know, like guest mentioned if you're looking for a quick replacement for the 074 the 084 It's gonna be really really really close. It's a little bit noisier. I got a little bit more distortion But it's it's really close so comparing, you know, this is 084 and 074 If we compare them, you know, the input bias is a little bit Lower on this 084 the voltage offset's the same The voltage supply is the same, you know, you can look in detail in the specs, but it's pretty much the same thing So if we well, let's say we're like, okay, you can't get 084 or 074 is like more completely Whatever so the first chip that's not from that family Another thing that's interesting is you notice both TI and ST both make TL 0708 X's so, you know, you do have two source suppliers. It's really nice but the next non TL whatever series that's available is the LF 347 which was like not available in TESOP, but had a pretty good specs. It has a slightly better slew rate It has a much better input bias 20 pico amperes It's got 40 milliamps output for challenge. It's kind of nice a little bit better gain with Game bandwidth products that basically means like, you know as you increase your gain the amount of bandwidth the frequencies You can pass reduced if you're dealing with audio. You're probably dealing with more than like 44 kilohertz or whatever so Keep that in mind depending on how much game you want if you're doing microphones or whatever It looks like the supply can be plus or minus 22 volts. It's looking detail. Maybe at the datasheet to look at the supply It's a high slew rate J-FIT input again get that standard quad Package Pretty simple design here. Let's look at if it has a minimum power supply Gonna like hunt for it Where's the Maybe they don't have it in the datasheet. That's kind of weird plus or minus 12 volts maybe Output voltage swing. I mean, I guess you could try running it at like plus or minus 6 volts I don't think you need to the absolute value is 18. They don't seem to really have the Vcc here Probably like six volts or so. It's probably the same as the 084 Okay, cool. So Your options are basically find it 074 that might have not the exact same specs you want but It's close enough because there's a lot of them in different families If you don't mind re-spending your boards we spin the board to use SOIC if that's available instead of SOP And then, you know, there are a couple other chips that are in a similar price range like the LF 347 if we you know if we go much farther in the pricing There are more chips, but they start getting more expensive like, you know, you're basically paying like 40 cents per chip instead of 20 cents There's like the BU 784 from Rome. So there's a couple options. So I think you know You're not totally out of luck But you know, like I said, you're gonna have trouble finding something that's as Cheap and as all-around good. So you might have to give up one thing whether it's price or You know noise or distortion or slew or input bias or whatever But it's probably gonna be priced because like like they mentioned it is like one of the cheapest op-amps you can get So there's not options available. So if you're making synthesizers, do not despair We there are options available for you Other o74s o84s or the LF 347 Yes