#1091 LM723 voltage regulator

Comments · 40

• JO

  @joeteejoetee · 4 years ago (edited)

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

  7

• SL

  @slordmo2263 · 4 years ago

  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....

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• PT

  @ptronix · 4 years ago

  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

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• GK

  @gkdresden · 3 years ago (edited)

  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.

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• RE

  @reidgraham3305 · 4 years ago

  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!

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• TI

  @Tinytotreaders · 1 year ago (edited)

  Tomorrow is my exam! Thanks for the video

• BO

  @boonedockjourneyman7979 · 4 years ago

  Genius

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• TS

  @tsec_kwr_37 · 4 years ago

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

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• PH

  @PhoenixRevealed · 4 years ago (edited)

  I&apos;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&apos;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.<br>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&apos;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.<br>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.

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• ED

  @educationdz202 · 4 years ago

  Very interesting indeed .. many thanks

• TV

  @tvelektron · 4 years ago

  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 🤔

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• TO

  @TomLeg · 2 years ago

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