temperature coefficient ? - Electronic Circuits Projects Diagrams Free

Screech · 30th May 2005, 05:59 AM

Temperature coefficient . what does that mean?

I'm guessing that if the teperatures in the zener rises, the reference voltage will not ?

instruite · 30th May 2005, 08:07 AM

Temperature coefficient is a factor with which the parameter (regulated voltage in this case) changes with the change in temperature

Dean Huster · 30th May 2005, 02:47 PM

Temperature coefficient (tempco) is associated with nearly anything in physics. In electronics, it's the driving parameter for thermistors which may have a negative tempco (most common) where the resistance decreases as the temperature increases or a positive tempco where the resistance increases as the temperature increases.

Wire has a tempco, a parameter represented by the Greek letter "alpha" and may be either positive or negative, depending upon the material of which the wire is made.

Capacitors have a tempco, non-NP0 ceramic types often having severe tempcos that make them totally inappropriate for frequency-sensitive circuits such as oscillators and filters. The NP0 (that's en-pee-zero, not en-pee-oh) ceramics have a zero tempco and change very little (nothing's perfect) with a change in temperature.

Transistors and diodes change their characteristics as their junction temperatures change which is why circuit designs must be such that thermal runaway is not a possibility. Thermal runaway is when a junction heats up, it conducts more, heats up more, conducts more, etc. until the junction is destroyed.

Carbon resistors have a tempco, usually positive where the resistance increases as temperature increases. For most applications, this isn't a problem. If the resistors are used in precision voltage dividers such as for instrumentation (voltmeters, ammeters, attenuators, etc.), then precision metal film resistors are used, both for better initial and long-term accuracy and for a severely-reduced tempco.

Dean

Screech · 31st May 2005, 01:08 AM

WOW.
I didn't know all that.
Thanks

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30th May 2005, 08:07 AM	(permalink)
instruite	Temperature coefficient is a factor with which the parameter (regulated voltage in this case) changes with the change in temperature __________________ Instruite http://www.icesociety.org ===================== Ideas that work, Concepts that sell. =====================

30th May 2005, 02:47 PM	(permalink)
Dean Huster	Temperature coefficient (tempco) is associated with nearly anything in physics. In electronics, it's the driving parameter for thermistors which may have a negative tempco (most common) where the resistance decreases as the temperature increases or a positive tempco where the resistance increases as the temperature increases. Wire has a tempco, a parameter represented by the Greek letter "alpha" and may be either positive or negative, depending upon the material of which the wire is made. Capacitors have a tempco, non-NP0 ceramic types often having severe tempcos that make them totally inappropriate for frequency-sensitive circuits such as oscillators and filters. The NP0 (that's en-pee-zero, not en-pee-oh) ceramics have a zero tempco and change very little (nothing's perfect) with a change in temperature. Transistors and diodes change their characteristics as their junction temperatures change which is why circuit designs must be such that thermal runaway is not a possibility. Thermal runaway is when a junction heats up, it conducts more, heats up more, conducts more, etc. until the junction is destroyed. Carbon resistors have a tempco, usually positive where the resistance increases as temperature increases. For most applications, this isn't a problem. If the resistors are used in precision voltage dividers such as for instrumentation (voltmeters, ammeters, attenuators, etc.), then precision metal film resistors are used, both for better initial and long-term accuracy and for a severely-reduced tempco. Dean __________________ Dean Huster, Electronics Curmudgeon Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines). R.I.P.

31st May 2005, 01:08 AM	(permalink)
Screech	WOW. I didn't know all that. Thanks