Forward Voltage of Schottky vs Temperature

[jaylar41]

Hello,

I've been looking for a Schottky diode which experiences an increase in forward voltage through the normal operating temperature range (-40C - 125C). I've only seen diodes in which the forward voltage decreases as temperature increases.

If such a device existed, I could use it for a temperature sensing application. I've researched plenty of thermistors and temp sensing ICs, but they don't have the right fit to what I'm looking for.

The reason I say Schottky is because I need the voltage to be under .7V (may be able to budge a little).

If someone knows of a part like this, I would appreciate a heads up. Thanks for any advice.

 

[ScottyUK]

Silicon carbide Schottky diodes have a positive tempco.

Sounds an unusual application - can you explain a little more?


----------------------------------

Sometimes I only open my mouth to swap feet...

 

[IRstuff]

why not just use an LM94022:

http://www.national.com/pf/LM/LM94022.html,

which runs off 1.5V

http://cache.national.com/ds/LM/LM94022.pdf

TTFN

Eng-Tips Policies FAQ731-376

 

[itsmoked]

How about a thermistor? Run it off anything u want.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jaylar41]

Thanks for the advice.

I'll look into the silicon carbide diodes. Hopefully there will be something with a low enough value to work with.

The reason I don't use temp sensing ICs is because it's an AC application and I do not want to build a voltage regulation circuit that will supply the Vcc. There very well could be something out there that has a Vcc max of +20V, but it would take a bit of searching.

The thermistor approach is what I'm working on right now, but I'm having trouble finding exactly what I'm looking for. If there was one that ranged from 20? to 200? in the temp range of 25C - 80C, that would be ideal.

The original schottky question was going to be a shot in the dark with my circuit. It's all speculation on an existing circuit (that's why I can't be adding too many components). Also, I'm not sure I'm at liberty to fully explain what I am doing. That's too bad for me I know, because that's the only way you can really help.

I've got some design ideas to try in the meantime. Any more advice would be great. Thanks again.

 

[IRstuff]

Without a well-regulated DC reference, a Schottky diode won't work, either. Not even sure you can get a thermistor solution to work well without a regulated DC reference.

TTFN

Eng-Tips Policies FAQ731-376

 

[sreid]

You might check this out for thermistor vendors.

http://www.temperatures.com/thermivendors.html