[sdiy] starter components -- one of everything?

[James Patchell]

In general, you can use TL072/TL082/TL052 pretty much to do all of the 
opamp duties.  Very rarely do I ever have to use anything 
else.  Personally, I tend to shy away from the quad opamps.  The main 
reason is that they complicate PC board layouts because of the position of 
the power pins.

The offset null inputs of single opamps allow you to trim the offset 
voltage of the opamp...in general, this is of very little utility.  It has 
been quite some time since I have used this feature.

For OTA's, I like to keep all three of the major types in stock.  At the 
low end of the spectrum is the CA3080E, which is the classic OTA.  Sure, it 
has fairly low performance, but it has its uses.  In the middle, there is 
the LM13600/LM13700/NE5517 type OTA.  I like these in those cases where I 
need a pair of temperature tracking OTA's for a design.  And of course, 
they do a good job at the usual OTA jobs as well.  And on the high end, 
there is the CA3280E.  This part has the lowest feedthrough, lowest noise, 
and the <sigh> highest cost.

For transistors...2n3904/2n3906 do most of the jobs.  You will also need 
some JFETs like the 2n4391....

At 02:54 AM 2/28/2005 +0100, Johannes Öberg wrote:
>I found a cheap surplus supplier, and now I'm wondering what OP-amps
>and OTA's are best to get for general purpose use. I see some op-amps
>feature "offset nulling". What is that?
>
>What I'm mostly considering building are a couple of compressors,
>filters, distortions and stuff like that, and various control stuff to
>make stuff MIDI-controlled. Are those packs of 4-opamps-in-a-DIL14 a
>good idea too keep things at equal temperatures or something?
>
>What's the difference between the different OTA:s? Can you safely
>replace one type with another in circuits, even if you don't really
>know what your doing? :-)
>
>Also, what transistors? Are arrays generally a good idea?
>
>(FYI, I don't know much about electronics so I'm mostly in the
>'build-other-peoples-circuits'-stage of my sdiy career, I'm on a
>poor-student budget and I'm not exactly and audiophile. I guess I'm
>looking for best bang/buck)
>
> > 2N3904 and 2N3906 transistors, > TL072 op amps
>
>Are these the cheapest, the best or both? :-) That is, why 2n3904 etc?
>(if there is a why)

         -Jim
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