[sdiy] Some more electronics history

[ChristianH]

Hi,

all this historical talk about the 3900 and its first use in synths made
me wonder - do any members of the O.F.F. (aka Old Fart Fraction :-)
remember introduction years for some key technologies, like operational
amplifiers, OTAs, 4000 CMOS logic, or - gulp - BBDs? 
When did e.g. the state variable circuit pop up for the first time? Or
something simple as LED technology, and there's probably some more that
we take for granted now, but that simply hasn't been around only a few
decades ago...

Do those inventions date back to the 60s, or did it all happen in the
early 70s?

Christian