how to calculate temp coeff of band gap reference..

[abhaykochhar2]

hii..
how to calculate temp coeff of non linear expression as in case of band gap reference... we get non linear graph of a voltage reference... then i took differentiation of it with respect to temperature with the help of synopsys calculator... now hw to proceed for calculating it temp coeff... do i hv to take average of dV/dT or take a particular instant of dV/dT and divide it by V at that particular instant...
help me out..

 

[allan_ecker]

A nonlinear graph means you have a circuit with a nonlinear temperature coefficient. If this is for a lab and you're expecting a straight line, then you probably need to fiddle with something in your setup (device scaling perhaps?)

However, if you're just trying to evaluate the "quality" of this bandgap (even well-designed bandgaps will move away from ideal), I'd almost recommend another measure: total excursion over likely thermal operation. For that, just measure top and bottom of the curve you get observing it over the likely range.

If you want to predict the bandgap's value at a given temperature I'd go beyond temperature coefficient to lookup tables or something. Assuming you don't mind having custom lookup tables!