Filament LED bulbs use very narrow strips containing the LED,
which look similar to filaments of an old incandescent bulb.

Here's a good picture:
http://www.aruana-led.de/

How are these filaments build?
I could imagine the it's "pretty normal" LEDs, but lots of them,
directly bonded to something? (There are references to COB)

And how does the driver look like?

*Update*:  

Found  [some really detailed images at alibaba.com](http://www.alibaba.com/product-detail/China-professional-LED-lamp-3-6W_1627675449.html)