[sdiy] couple of (beginner) questions

[Nils Pipenbrinck]

Ok, after just reading the list for a couple of weeks I now want to start to
build something..


For the start I decided to do a vco.. I took a look at the asm1 circuit, and
it looks quite easy to do a pcb for, and I heard, that this vco is a good
choice. However, I still have a couple of questions:

The original(?) circuit I have here uses a MAT-02 transistor-pair as the
exp-converter.. Can I simply change that one with a 2SC1538? (I'm not able
to get the MAT-02 here in germany, but 2SC1538 are cheap and easy to get).
Another choice would be to use the LM394, which is available but expensive..
Which one to choose? (also: It would be very nice if someone could send me
the 2SC1438 datasheet... I haven't found it anywhere..)


And now for a real bloody beginner question:

I know that I need a tempco to get rid of the ambient temperature drift.
However, the only temperature sensitive resistors I am aware of are NTC and
PTC resistors.. I searched my favorite web-shops for a thing called "tempco"
but found nothing. (as I'm typing this I strongly feel like I'm starting a
new variant of the famous "I searched for the any key, but didn't found it
on my keyboard" joke right now..).

Where can I get a tempco? Or is it just a synonym for PTC? (don't think so
because PTC's and NTC's are not linear)

Ok, that's it for now,
        Nils Pipenbrinck