[sdiy] 4069 VCO to get started? My answer

[Nicolai Czempin]

Hi,

I've been asked whether I think the 4069 VCO is simple enough for my 
tastes. While it looks interesting, and I'll surely build it one of 
these days. It is still not what I was looking for. I do have enough 
other designs to try out in the meantime, so you don't have to think up 
any new ones :-)
Let me explain briefly why I won't be using the 4069-based design for now.

As I've mentioned before, I come from a software background. When we had 
electronics at school, I was most at home once things started to cross 
over into the digital world. Combining gates of all kinds, or even just 
NAND, seemed so natural to me. Even if it was all just done on paper.
My aim, however, is to learn the fundamentals, so for quite a while I 
want to stay analogue (BTW is spelling this word with or without the 
"ue" a British vs. American thing or are there other factors involved?).
So, while it is probably an interesting approach (and apparently quite 
successful, since so many people seem to be recommending it), the mere 
fact that it is a CMOS-gates-based design makes it a step up from the 
basic analog stuff. Take any introductory electronics book, and they 
will start, with the basic components, with both CMOS and digital issues 
being found in the late chapters if at all. And with CMOS there's always 
a warning that you really have to watch that static electricity or 
you'll damage the compontents. Although a friend of mine tells me in all 
the years he's worked with CMOS stuff, he's never used an antistatic 
band, and he's never damaged a CMOS component.
Note that I'm not saying that it really is harder to understand, after 
all, abstraction is meant to make complicated things easier to 
understand (a gate vs. all the components that are "inside". But I want 
to learn this stuff "the traditional way".

Now, it may seem that I'm contradicting myself, by using op-amp-based 
designs. Perfectly correct, and I *will* want to build a VCO using 
discrete components. I guess I'm drawing an arbitrary line at the 
analogue vs. digital border for now.

That's why I called the circuit "impure" BTW (tongue-in-cheek, of 
course), in case you hadn't realized.

I'll report my progress in my weblog as soon as I have sufficient 
internet access.

mfg Nicolai