[sdiy] 4069 VCO to get started? My answer

[Nicolai Czempin]

Laurie Biddulph wrote:

>Hello Nicolai,
>
>Although the 4069 is fundamentally a logic IC it is actually used in this application as a linear device and utilises the fact that at lower power rails the gates can actually be treated as linear/analogue devices. This, therefore, does make the 4069 a suitable device for your initial requirements.
>  
>
Okay, I'll accept it even if I can't quite follow...
What kind of "analogue devices"? My minimal electronics knowledge has me 
remember that an Integrator is one use for an op-amp. Same with a 
buffer. Not sure yet about the Schmitt-trigger and the modulator. But 
why all that works with just inverters beats me.

So it seems that using an IC which has all these on one chip is a 
sensible optimization, both regarding space and cost. Neither is of the 
highest priority to me right now, while simplicity is.
And of course availability at my home shop (easy access). Well, it 
scores well in that regard:
http://www1.conrad.de/scripts/wgate/zcop_b2c/~flN0YXRlPTcyMDA5ODE0MQ==?~template=PCAT_PRODUCT_DETAILS_DOCUMENT&object_guid=A50D7B3B5FF4615AE10000000A010220&master_guid=&master_desc=&master_group=&master_typ=&master_first_row=&master_last_row=&p_load_area=204220&page=&p_sortopt=&max_tab_items=10
And, wow, just 51 (Euro-) cents a piece! That sounds like an extremely 
good deal.

I'll still take the route of my "dead ends", but I sure know what lies 
ahead in the direction of progress :-)

And regarding the multiple outputs: Looking at the schematics it doesn't 
look very hard to add the sawtooth once you have the "pulse" :-)


BTW to all those people (in the original thread) that are recommending 
that I should buy a scope etc., I repeat what I originally mentioned:
I *have* an oscilloscope, of the two-channel, analogue 30 MHz variety. 
Have a look here:
http://www1.conrad.de/scripts/wgate/zcop_b2c/~flN0YXRlPTI4MDM0MzMzMzA=?~template=pcat_product_details_document&object_guid=3D7F673C9D7BFB15E10000000A010221&p_load_area=1113020&master_guid=&master_typ=&page=1&p_sortopt=ZARTSORT
(Text is in German, couldn't find an English version. It does seem to be 
a "relabeled" version of another one, but I don't know what the original 
is called).
 I will also buy a power supply (just need to find the time), variable 
*of*course*, with *three* outputs.
http://www1.conrad.de/scripts/wgate/zcop_b2c/~flN0YXRlPTI4MDM0MzMzMzA=?~template=pcat_product_details_document&object_guid=1F4FA03CFC813325E10000000A010221&p_load_area=1111015&master_guid=&master_typ=&page=2&p_sortopt=ZARTSORT

Regarding soldering iron, I do have one, but I don't know how good it 
is. I will take a close look exactly what to get once I actually start 
soldering. For the moment I'm just sticking wires and things into a 
breadboard.

>This `non-digital' approach was used in several synth designs including the EDP WASP which I am reviving in my project the Pixie which you can find on my website below along with all the schematics. In this instance the 4069 is used in the LFO as a triangle/sawtooth oscillator.
>  
>