[sdiy] CMOS & CD4007 Questions?

[René Schmitz]

Hi Scott and List!

At 11:34 27.11.02 -08:00, you wrote:
>FWIW, I can relate a 4069 experience.  I was building a René Schmitz VCO that
>uses all 6 inverters.  I put the schematic together and had a strange
>problem.  Turns out that René had used different inverters than I had for the
>different functions of the circuit.  When I repinned mine, it worked
>properly.  René was also able to duplicate my problem by repinning his.  6
>inverters.  I'm not sure if the chips we used were of the same maker, I
>believe not.  

I think so too. 

>At least for us, the inverters within that same chip did not
>behave identically.  Ever since then, I've started to note pin numbers on my
>schematics, at least for CMOS.

That was caused (as far as I understand/recall it) by the different layout, 
precisely the different parasitic capacitances. The version which oscillated 
had an amplified waveform sitting next to its input, which was also dependant on 
this input. I.e. a feedback loop, which oscillated on high frequencies.
You have to use the gates in their natural order, i.e. the output drives the 
adjacent input, all other ways do oscillate.

>>Then there is the CD4007 which falls between the analog and digital realm,
>>more than most the other chips. A number of manufactures spec it and
>>application notes use it in the analog domain. So my main question is how
>>consistant is the CD4007? Are there issues with different manufactures chips
>>working different?

You shouldn't use the 4007 as single transistors where you make great demand on 
specific properties. Unless you don't care if you have to select them. 

Cheers,
 René


-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159