[SOLVED] LM334 general opinions

[d123]

Hi,

Using page 11 circuit of the LM334 datasheet for a 1.2V reference this afternoon to get a 1V reference (blow on it to raise Vout, fan it by hand to lower Vout...), I got to wondering:

Do people actually use this IC for anything serious?

When is it used in mass production?

What are other members' opinions and experiences of this component?

Could you say it was good for its time, i.e. better than a vacuum tube or a Philbrick op amp?

I've never enjoyed prototyping with it as it has poor tempco (54 mV to 74 mV across temperature range from a nominal 64 mV) so always want to use it but know/believe it degrades any circuit it is used in, temperature-compensated or not. Maybe I'm wrong.

 

[KlausST]

Hi,

My datasheet page#11 shows just " 5 Package Information"

https://www.st.com/resource/en/datasheet/lm234.pdf

I can't answer your question ... but you are free to use any other voltage reference (or other IC) you prefer.

Klaus

 

[danadakk]

The short answer is what are the specs you are shooting for ? This is a part ~40 years old.

Its tempco is 1 % for every 3 C rise, yes, its not todays state of the art. You can get
processors today with onchip Vref good for +/- .1% with 30 ppm drift.


Regards, Dana.

 

[d123]

Hi Klaus,

Hi,

My datasheet page#11 shows just " 5 Package Information"

https://www.st.com/resource/en/datasheet/lm234.pdf

I can't answer your question ... but you are free to use any other voltage reference (or other IC) you prefer.

Klaus

Okay, fair enough: I have the TI LM134/LM234/LM334 datasheet, https://www.ti.com/lit/ds/symlink/lm134.pdf, and it was page 13 (not 11) for the 1.2V reference, figure 25. It would be nice to know how Vout is calculated, approximately at least, I am having difficulty understanding the output from the input. I'll play a bit more later with the breadboard version I did to see if I can understand it, it seems to be something to do with a voltage divider and also possibly Vin value matters.

Regarding the questions about who and why they use it, I'm just curious as it's an active part (only two versions are NRND in the TI datasheet) and is clearly used/sold a lot.

Anyway, thanks.

--- Updated Sep 25, 2020 ---

Hi Dana,

The short answer is what are the specs you are shooting for ? This is a part ~40 years old.

Its tempco is 1 % for every 3 C rise, yes, its not todays state of the art. You can get
processors today with onchip Vref good for +/- .1% with 30 ppm drift.


Regards, Dana.

As I just said above, I'm just curious about who uses it and in what kind of professional circuits - presumably those not needing tight regulation - because it's an active part so must be used a lot, despite being a very old IC and far less stable across temperature than other ICs like e.g. the REF200.

I was trying to see if I could replace the LM4041 1.225V voltage reference with a 1V reference so I can get a little more headroom in another circuit. The LM334 voltage reference circuit might suffice as I only need loose regulation for a constant current op amp/NMOS circuit. It's not a vital circuit, 1.225V is do-able, I'm just looking at home-brew alternatives in case I can throw together a decently stable 1V or even 0.5V - 0.8V reference without needing to buy anything, just using what I already have.

Wasn't being rude about venerable LM134/234/334, BTW, in context and in its day it must have been a great part, just as the 555 was/is.

Thanks.

 

[KlausST]

Hi,

your schematic output has a 1.2V output has a series resistance of 3.6kOhms.
Connecting a 18k from (3k6) output to GND will cause the output to become 1.0V - without any degrading of the performance (on a first sight).
.. in my eyes the simplest solution.

Klaus

 

[danadakk]

Over here quite a few offerings for 1.2V Vref

PMIC - Voltage Reference | Electronic Components Distributor DigiKey

PMIC - Voltage Reference are in stock at DigiKey. Order Now! Integrated Circuits (ICs) ship same day

www.digikey.com

You could always use a Vdac with an onboard Vref as well.....


Regards, Dana.

 

[FvM]

Why are you using a temperature sensor (PTAT current source) as voltage reference? There are so many temperature independent voltage references on the market.

 

[d123]

Hi,

Why are you using a temperature sensor (PTAT current source) as voltage reference? There are so many temperature independent voltage references on the market.

I just couldn't resist trying, even knowing what to expect from the part. In the end, I'll divide down the LM4041 1.223V with a 22k/100k divider to get around 990mV.

 

[shredder929]

At first glance I would think its popular for hobbyist tinkering or educational uses, but these are stocked at the tens of thousands.

My guess is that it's used in boards from decades ago still in production that can't or won't be updated but are still in use. Maybe it's used in extreme cheap electronics like toys being sold in developing countries that are expected to fail in under a year anyway.

 

[danadakk]

Its great for long cable run T sensing as its a T dependent current
source. A tradeoff from doing it wirelessly, both have advantages.
In case of wireless one needs a remote power source/battery/solar
cell kind of approach, whereas a LM334 is powered from cable source.

I have used both in a property management system, ultimately the LM334
was lower cost, more reliable than the wireless approach.. However required
2 wire cable run/installation is a cost factor. LM334 in this application, to
improve accuracy, was caled in an ice bath, eg. out of the box its not very
absolute accurate. Its G curve is accurate, just not its initial offset.

Regards,. Dana.

 

[d123]

Hi,

In case anyone is interested in this article and hasn't read it before:

**broken link removed** by Paul Rako. He discusses the device a little and his experiences with it a bit.