#1091

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2 жыл бұрын

Episode 1091
This IC circuit is very similar to the the circuit I show in: • #1091 LM723 voltage re...
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@slordmo2263 2 жыл бұрын

Yep, a classic 'building block' IC..... used to see these in 'ham' 12V supplies all the time, even saw how they used them in 80's Weller temp. controlled irons... that's why they still exist....kinda like the 555 timer.... infinite uses....

@joeteejoetee 2 жыл бұрын

Don't forget that small capacitor on the frequency compensation pin, or else you may make a power VLF frequency generator !

@reidgraham3305 2 жыл бұрын

Thanks, that was the most useful 723 walkthrough I've seen. I recently made a 723 based supply which used some new uA723 chips from Digi and found them to be quite noisy. I dug through my junk box and found an old LM723 which was much much better. I guess they don't make them like they used to!

@gkdresden Жыл бұрын

A nice old versatile current / voltage regulator chip. But there are two other old chips for this purpose. You can also have a current regulation / current limit functionality for your LM317 / LM337 just by adding 1 transistor and 1 resistor. Because it works with a 1.25 V reference you can always have your potentiometer at the same position. Or you can use an L200 which comes in a nice 5 pin TO-220 package and you only need to add 1 resistor for current regulation / current limit. The references for voltage / current are a little bit strange (2.77V / 0.45 V). In both cases you can go to 1.5 A and if you need more you can add an external pass transistor.

@ptronix 2 жыл бұрын

Ah the good old 723, built many power supplies in the past using it. I think the biggest one was 13.8 volt at 25 amps

@PhoenixRevealed 2 жыл бұрын

I've been doing electronics as a hobby or career for nearly 50 years, and last year when I needed to design a low-dropout lead-acid battery trickle charger I turned to the 723 because I knew it had all the features I needed. I still had a couple of 40 year-old specimens in my anti-static foam lined parts drawers, but I figured it wouldn't hurt to order some more in case they ever became hard to find, but for now at least I had no difficulty finding new stock in hobbyist quantities. One thing you glossed over in your description was the zener diode between Vout and Vz. In fact at one point you even covered it up on the schematic with your finger and then never mentioned it again. In all the years since it was originally released in 1967 I have never seen an application note or project in the wild that used it, or even explained what it is for. Vz is not even brought out to a pin on the metal can package and the data sheet says if you need this function with that package (whatever it's for) then you should connect a discrete 6.2V zener to Vout. A couple of years ago I posted questions in all the online electronics forums I could find and not a single person replied with useful information. I suspect it was intended as a level-shifter to allow control of a negative rail pass transistor below chip ground, but I wonder if it has ever actually been used in any real circuit or product.

@ralphj4012 2 жыл бұрын

I believe Vz is used when you require an external transistor for increased current. Search for LM723 with external pass transistor.

@SeanBZA 2 жыл бұрын

Yes, in the app note from TI exactly for that, and keeps the internal opamp from saturating, when attempting to drive the internal pass transistor too close to the negative rail. Keeps the internal circuitry stable, as that opamp cannot pull too close to ground. Ideally you want to keep pin 9 and 4 (DIP package) reasonably close to each other, so the zener is used to give that 6V2 step, by using basically the emitter base junction of a transistor in reverse, along with the base collector junction in forward bias to temperature compensate it. The most critical diffusion in making the wafer, so it is monitored by test structures and probes during manufacture, to make sure it is correct. Forms all the 3 zener diodes in a single step. along with every other transistor base emitter junction. For a 40 plus year old design it is still quite good, with a reasonable performance as well, plus is quite versatile. Still available, and yes, there are better more modern chips, but still being able to handle 40V as input voltage is still an achievement, and I have used them as references before, they are quite good at that, even being good enough to use for power supplies with 0.1% output voltage tolerance. Used them to make suppressed zero meters, making the IC a current sink, that kept a defined reference voltage, so the meter could have a suppressed zero, to make best use of the range and display markings.

@PhoenixRevealed 2 жыл бұрын

@@ralphj4012 Nope, that's not it.

@PhoenixRevealed 2 жыл бұрын

@@SeanBZA Thanks, that makes perfect sense. Do you have a number for the app note?

@ralphj4012 2 жыл бұрын

Search for 0900766b800769ed.pdf (which shows Vz being used in a negative voltage regulator) and lm723-440706.pdf, select the Mouser link (which shows Vz being used in high voltage and a current limited supply)

@tvelektron 2 жыл бұрын

An very interesting and universal component, no question about it. Only would you really use a 723 for a new (DIY) project or would you rather use more modern components 🤔

@tseckwr3783 2 жыл бұрын

I think Astron pretty much supported the LM723 production lines all by itself.

@IMSAIGuy 2 жыл бұрын

even some switchers use the 723

@norbertoreigada6698 13 күн бұрын

Como acionar tradução?

@norbertoreigada6698 13 күн бұрын

Onde tradução?

@norbertoreigada6698 13 күн бұрын

Como acionar tradução?

@educationdz202 2 жыл бұрын

Very interesting indeed .. many thanks

@boonedockjourneyman7979 2 жыл бұрын

Genius

@bayareapianist 4 ай бұрын

I'm wondering if I need a 0-30V power supply, can i connect the lm723's ground to let say -8V? What do i need to get a nice 0-30V out of it?

@IMSAIGuy 4 ай бұрын

I've biased LM317 below ground to get zero volts, I assume you can do something similar to the LM723. be careful not to go past the max voltage for the part

@TomLeg 2 ай бұрын

$12US at Digikey, similar at Mouser, bit cheaper at Rochester

@rtacconi 2 ай бұрын

Do you know an equivalent IC that can work at 55-60v?

@DuroLabs85 Жыл бұрын

Hello, I am new to this IC, I have the old To-100 metal can package IC and this package dosent have the "Vz" pin Which is present on the Dip package can anyone tell is that pin Important or not I want to Make a 0-30V 0-5A power supply using the IC.

@IMSAIGuy Жыл бұрын

Not needed

@DuroLabs85 Жыл бұрын

@@IMSAIGuy Thank You For replying :)

@t1d100 2 жыл бұрын

Great video and introduction to an IC that I did not know about. It seems to be the (mostly) complete front end for a DIY linear power supply. So, why do manufacturers use individual components? Rhetorical; I know the answer is economics. Mouser prices start at $13 = ouch.

@__--JY-Moe--__ 2 жыл бұрын

OMG! just what I was thinking! the new TI stuff is getting so expensive!! but, oh man ! super duper! not trying 2 advertise, but! ''electronic goldmine'' has some super old new stock!! seriously!! throw me that opinion! good luck with it!

@yassirc3681 10 ай бұрын

Are there any variable voltage regulators on the market that you would recommend?

@IMSAIGuy 10 ай бұрын

LM317

@98xjdriver 2 жыл бұрын

My astron rs35 is basically an lm723 with a bunch of pass transistors.

@rusty1187 Жыл бұрын

I compared the RM-35 and the VS-35 schematics to learn how to build different output voltage supplies. add as many pass transistors as to current draw needs!