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# Precision low reference voltage

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#### flote21

Hello guys,

Im my current desing I have the next 2V reference voltage

However I need to exchange it by a 0.5V reference voltage. I was checking in Digikey and I did not found any commercial part with such a low value. Could use a Zener to get this low value? I am afraid the zener is not giving me the enough accuracy: +-1%...

Note: It would be great to find a part with the package: SOT-23.

Greetings.

#### KlausST

##### Super Moderator
Staff member
Hi,

How much thermal drift can you accept?

2mV/°C?
Then a usual diode (1N4148) may produce around 0.65V, A schottky diode (BAT54) around 430mV.
Mind: cathode to GND.

Klaus

### flote21

Points: 2

#### FvM

##### Super Moderator
Staff member
An obvious solution is comprised of reference, voltage divider, OP buffer. Buffer may be avertable depending on the load impedance.

#### flote21

2mV/ºC is good for my application. Thanks for the advice
The proposed solution of FvM is goof bu I will need to redesign my PCB....I will try with the normal deiodes.
Thanks,

#### FvM

##### Super Moderator
Staff member
There are obvious reasons why precise shunt references below about 1V aren't feasible. You need to switch either to series reference or divide a higher reference voltage.

200 mV and 400 mV references here -

.5V Vref -

Regards, Dana.

Last edited:

#### BigBoss

Divide the Reference Voltage by Precision Resistors then use an OP_AMP as a Voltage Follower( Low Drift $V_{offset}$Model).

#### d123

Hi,

2mV/ºC is good for my application. Thanks for the advice
The proposed solution of FvM is goof bu I will need to redesign my PCB....I will try with the normal deiodes.
Thanks,

Due diligence is to check datasheet electrical specifications and relevant graph for forward current versus forward voltage, then check electrical specifications and relevant graph for forward voltage versus temperature - the variation with current is large and with temperature is also quite large, over a small temperature range it might be tolerable, from 0°C to 85°C it becomes undesirable, IMO.

Staff member

### flote21

Points: 2

#### Easy peasy

plain resistive divider off the 2V ref will be fine - buffered by an op-amp if required ....

#### flote21

do you think a simple divided resistor with 0.1% of tolerance and 15ppm will be enough to keep 0.5Vref at 50ºC? According to the theroy the error is minimum...but I don't know if maybe a diode will provide a better performance...

#### FvM

##### Super Moderator
Staff member
You can know. A silicon diode has a forward voltage T.C. of -1.9 mV/K, or about -3000 ppm.

d123

Points: 2