Tempco EN article

[Tim Cockram]

Hi

Using such a low impeadance scheme could cause a problem with drift due to self heating of 
the tempco resistor:  eg 15V across a 1K resistor  produces a power disipation of 0.225 
Watts.  I don't have too much experience with tempco resistors, however I am inclinded to 
believe that this will cause the temperature of the resistor to rise significantly and hence 
change the resistance.

There is a solution though:- maintaining the exponential transistors at a fixed temperature 
in an "oven"(as per Rick Jansens schematic).  This technique was used for years to produce 
accurate crystal oscillators.  Has any one tried this? and if so with what results?
 
Regards

Tim


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Tim Cockram
E-mail: tim at redragon.demon.co.uk 

Phone:-UK-1222-384041
Fax:-    UK-1222-390326

"Sociology is the study of those who don't need studtying by those who do."
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