[sdiy] Temperature Compensated VCO attempt - help?

[ASSI]

On Thursday 30 January 2003 14:12, Scott Bernardi wrote:
[...]
> > > http://home.attbi.com/~sbernardi/elec/og2/tempcomp_vco_theory.htm

You mention EN#113 and two extra current mirrors not in the data sheet 
for the LM13700. I've just drawn the CA3080, CA3280 and LM13700 
schematics with just the current mirrors, differential pairs and 
linearizing transistors (tied as diodes) for reference and I'd like to 
include the extra mirrors. I'd think that there should be a npn->pnp 
sink to source configuration (slightly simpler than the one in the 
CA3280), but maybe EN#113 had more specifics?

A note on bandgaps: the PTAT characteristic is a (pretty good) linear 
approximation. Hence the compensation is perfect for only one or two 
temperatures after trimming, depending on where you put the trim 
point(s). You can of course try to remove the curvature by including 
the quadratic term or piecewise linear approximation.


Achim.
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