is there electronics drawing app that integrates well with kde (4 or 3) ?

is there electronic components library for qelectrotech ? (stuff like opamps and gates and resistors) ?

The only one I know that would directly meet your needs is xfig which is not a KDE program and you may find it off-putting because the interface is very old (the program was begun for Unix in 1984) but it exports in pretty well every format, though SVG is a little flaky, and so you can output to any KDE program. It might be worth trying xfig for the electronic components and then see if exporting via SVG to Karbon works. (If Karbon accepts PS or EPS input, you may get better results).

There is something called ktechlab (which is more than circuit drawing app though). The KDE 3 version seems to be quite nice. There is an outgoing effort to port it to KDE 4 but looks like the KDE 4 version is not really ready yet.

You can check their development mailing list: ktechlab-devel [at] lists.sourceforge.net