someone please explain this part to me

[Gibson486]

Is it me or is this just a xener diode with a breakdown voltage of 1.2 V? The part itself cost $7! However, they market this as a voltage reference. couldn't I just use a xener diode?

 

[PottedMeat]

I dont think there are 1.22V zener diodes. Judging by Digikey's LM113 parts list, it looks like you're paying extra for temperature stability. A LM113 seems to have a 10ppm/degC temp coeff while the next part in line has 75ppm/degC which may be important in a A/D converter, probably others that I cant remember right now.

 

[Born2bwire]

Temperature stability typically 1% over-55°C to 125°C range (LM113), 0°C to 70°C (LM313)

I'd say that'd be a primary reason why this is comparitively expensive. Off the top of my head, compare it to a 1N5221B. That zener diode has a breakdown voltage of 2.4 V, but a temperature dependence of -0.085 %/degree C.


EDIT: Curse you potted meat!

 

[davesaudio]

suspect it takes much more current to get a zener over it's knee?

 

[bobsmith1492]

It's a (kind of) precise voltage reference. You can use them as references for A/Ds and/or instrumentation amps; for example, you'd reference your signal to 1.22 volts so the analog value can vary above and below but stay within range for a 2.5V A/D input.