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Temperature Coefficient Zener Diode

Hi All.

 

The attached circuit has two zener diodes, one 3V3 and the other 6V2.

 

Both diodes (BZX384) show a linear negative temperature coefficient

between 20 and 180 degrees Centigrade, whereas the 3V3 should be

-2.4mV/degree C and the 6V2 diode +2.3mV/degree C.

 

I have not changed the models. I hope someone can tell me I am an

idiot or I will have lost faith in the temperature modelling.

 

Thanks,

 

Keith 

 

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Hi Keith,

 

Thank you for your post.

 

Please may I ask what you are trying to do? Also, please may I ask for more details on your setup.

 

Kind regards,

YD

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Hi Yusuf.

 

I wanted to create a constant voltage, similar in action to a zener diode,

with near to zero temperature drift. To create this I was going to use the

combination of a zener diode and bipolar transistor. I have looked at using

shunt voltage references, but they all rely on a low impedance ground

because of the circuitry contained within. They are not suited to being

operated in series with a resistor in the anode and cathode.

 

Whilst pursing this task, the circuit I designed did not have the thermal

characteristics I was expected. Following on from this, I swept the

temperature of a BZX384 6V2 to find it's temperature coefficient

was negative rather than positive. The same negative coefficient

applied to the 3V3 diode. The circuit I presented was my test

circuit which need not be any more complicated for this purpose.

However, I should have only placed one probe on circuit so the resulting

graph had a much limited range of about 100mV.   

 

Basically, I should have just asked the community where the 

temperature coefficient  was stored the the BZX384 model, and, if not

included, what should it be. 

 

 

Thank you,

 

Keith

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Message 3 of 4
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Hi Yusuf.

 

I wanted to create a constant voltage, similar in action to a zener diode,

with near to zero temperature drift. To create this I was going to use the

combination of a zener diode and bipolar transistor. I have looked at using

shunt voltage references, but they all rely on a low impedance ground

because of the circuitry contained within. They are not suited to being

operated in series with a resistor in the anode and cathode.

 

Whilst pursing this task, the circuit I designed did not have the thermal

characteristics I was expected. Following on from this, I swept the

temperature of a BZX384 6V2 to find it's temperature coefficient

was negative rather than positive. The same negative coefficient

applied to the 3V3 diode. The circuit I presented was my test

circuit which need not be any more complicated for this purpose.

However, I should have only placed one probe on circuit so the resulting

graph had a much limited range of about 100mV.   

 

Basically, I should have just asked the community where the 

temperature coefficient  was stored the the BZX384 model, and, if not

included, what should it be. 

 

 

Thank you,

 

Keith

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Message 4 of 4
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