I found a discarded Keithley meter with a burnt board. It had one of these voltage references (labeled SL40057, crossed to LM399) and some OP177 precision op-amps elsewhere on the board too (Similar to LT1001). So I pulled them off the board and built the 10V portable calibrator shown on the LM399 datasheet. Works perfectly, cost me nothing to make. Thanks for showing the guts of the device, quite interesting!
Great video! I appreciate you walking us through all the math associated with the data sheet and explaining the PPM and temperature drift factors. Definitely learning a lot on your channel! Thanks!
In my travels I found its baby brother, LM3999, in a TO92 plastic package. The zener and heater circuits both share a pin for V- which knocks accuracy down a bit, and boy does that thing run HOT!
Correct maybe, but there is a diode from pin 4 to pin 2 , heater resistor to zener diode ground inside the chip. I connect all vref voltage ouput ground direct, as short as possible, to pin 2 at LM399.
I have been using this chip and its lower cost variants a lot. This one is extremely useful in circuits requiring top stability. One important thing to remember when using these stable parts. Never use any trim pots for fine adjusting them. Trimmers are not stable at all having several instability mechanisms. Use instead digipots.
Nice video again. Can you check stability with heater off, also with the "topless" component if it still works? Perhaps blow cold air in it? I am very interrested in the results.
Well, the datasheet did say it was all on a monolithic substrate :) But before seeing it assumed it was a separate heater too. In fact I wonder if a separate heater would be better. Monolithic should have a steeper temperature gradient, no? ...and I could never bring myself so sell these beauties!
I'm going to have to go read the data sheet, mainly because I want to see how they built that opamp circuit to be stable enough to be a worthwhile buffer. Curse you, sir, for making me go do some research! 😀
Is anybody knows, why are the zener diodes in that kind of precision component not bypassed by capacitors in the internal schematic? wouldn't that reduce the output noise?
made with Elf magic! @ Keebler! but in California, it's Parts Per Macintosh! did I learn something today? yes? I'm developing intelligence just watching U'r show's! good luck!
I found a discarded Keithley meter with a burnt board. It had one of these voltage references (labeled SL40057, crossed to LM399) and some OP177 precision op-amps elsewhere on the board too (Similar to LT1001). So I pulled them off the board and built the 10V portable calibrator shown on the LM399 datasheet. Works perfectly, cost me nothing to make. Thanks for showing the guts of the device, quite interesting!
Great video! I appreciate you walking us through all the math associated with the data sheet and explaining the PPM and temperature drift factors. Definitely learning a lot on your channel! Thanks!
Having palpitations here watching you sacrifice one of those rare old classics. Good video as always though
In my travels I found its baby brother, LM3999, in a TO92 plastic package. The zener and heater circuits both share a pin for V- which knocks accuracy down a bit, and boy does that thing run HOT!
I found one inside a TTi-1906 5.5 Digit bench DMM too, weird little thing, turns out newer revisions of the same meter use LM399s.
Correct maybe, but there is a diode from pin 4 to pin 2 , heater resistor to zener diode ground inside the chip. I connect all vref voltage ouput ground direct, as short as possible, to pin 2 at LM399.
I have been using this chip and its lower cost variants a lot. This one is extremely useful in circuits requiring top stability.
One important thing to remember when using these stable parts. Never use any trim pots for fine adjusting them. Trimmers are not stable at all having several instability mechanisms. Use instead digipots.
wow! I thought that was going to be a very boring design too, wasn't expecting that. Though anything with a heater is still really interesting.
Nice video again. Can you check stability with heater off, also with the "topless" component if it still works? Perhaps blow cold air in it? I am very interrested in the results.
These things are unbelievably good for their price, I stocked up on a bunch
Ian Johnston might want them for his PDVS2mini
He's using the AH spec part, and I would say buying new from manufacturer. You can't be using "inherited" reference parts for a $300 calibrator.
I have a set of about 8 of these, given to me by Jim Williams of National Semiconductor and later Linear Techhnology (LTC).
Nice video! I like it when you explain those datasheet 'concepts'.
"It's a very very good part", and a very very good video too!
Well, the datasheet did say it was all on a monolithic substrate :)
But before seeing it assumed it was a separate heater too. In fact I wonder if a separate heater would be better. Monolithic should have a steeper temperature gradient, no?
...and I could never bring myself so sell these beauties!
Monolithic more stable, as there is little temperature drift across the device, and faster response as well.
I'm going to have to go read the data sheet, mainly because I want to see how they built that opamp circuit to be stable enough to be a worthwhile buffer.
Curse you, sir, for making me go do some research! 😀
The trick is to also use an expensive chopper opamp! Opamp's are also known to be extremely stable under temperature change which helps.
Is anybody knows, why are the zener diodes in that kind of precision component not bypassed by capacitors in the internal schematic? wouldn't that reduce the output noise?
made with Elf magic! @ Keebler! but in California, it's Parts Per Macintosh! did I learn something today? yes? I'm developing intelligence
just watching U'r show's! good luck!
Isn't that sacrilege ?
Get out your oven mitts.
Eh, I would like to get one