[sdiy] Compensating PTC and NTC resistors

[Paul Perry]

There is no point obsessing over this.

Given the range of specifications for the PTC resistor, if you want
precision, you will have to tweak the final unit, while raising and lowering
the temperature of the circuit. Not easy at all.

Using a metal film resistor to tweak the coefficient of the PTC, will get
you closer to the ideal world. Whether its own coeff is +100 or -100.

If you want to do better, then you can use a thermostatically controlled
oven - or you can make a micro sized oven, using the transistors on a chip
system invented by Jim Williams.

Note that a PERFECT synth, would be as stable as a digital one - I'm not
sure everyone would want that ;D

Paul perry Melbourne Australia