[sdiy] Complementary transistors and other questions

[Johannes Öberg]

I'm ordering some stuff from an electronics surplus supplier, and
thought I'd stock up on some cheap parts since I'm already paying for
postage.

Now, I would have ordered some genpurp transistors like bc547 and
bc557, but they don't have "matching numbers". What would be the
drawbacks of using say bc548 together with bc307 ? I'm just assuming
they come in complementary pairs for a reason.

Btw, does a 3:1 ratio of NPN vs PNP seems like a good idea? Most stuff
seems to use alot more NPN's.

Another question is about opamps, can I use LP324 in place of LM324? I
know people say the 324 sucks in many places, but is ok for LFO's and
stuff. The LP324 seems to my untrained eye to be only a better specs /
lower power LM324, but theres probably a catch.

Also, non-matched transistor arrays, are they useful for anything? I'm
thinking they would be "sortof" matched, and thermally coupled. Right?

Does DIL20 have the same distance between the rows as DIL18 ? Or is
the row spacing not standardized?

/J