[sdiy] Newbie question regarding the 4069 VCO

[James Howe]

As I've mentioned before I'm relatively new to both electronics and DIY  
synth work.  I have managed to build a Fatman and get it working and I  
consider that at least a minor accomplishment.  I've been reading books on  
Electronics in an attempt to increase my knowledge about how these things  
work.  I understand them from a high level conceptual view, but I'm still  
trying to understand them from an lower level electronic view.

To that end I've been studying the 4069 VCO found at  
http://www.uni-bonn.de/~uzs159/vco4069.html and reading the various  
e-mails sent to this list concerning how it works.  Overall I understand  
how it works, the integrator generates a ramp, the Schmitt trigger resets  
the ramp generating a sawtooth, etc.  What I don't fully understand is why  
it works the way it does.  I'd also like to understand more about why  
certain components were selected.  Why the particular transitors, why the  
1N4148 diode, etc.  I'm trying to work though these things myself but I  
know it would help me a great deal if people could sort of walk through  
the various design aspects, why certain values/components were selected,  
and in general how it works from a lower level.

Thanks in advance.

-- 
James Howe