-=> Roy J. Tellason said to Greg Mayman
 -=> about "BAG OF CHIPS" on 01-14-04  04:06.....

 RJT> This wasn't my doing,  though.  Reminds me somewhat of assortments of
 RJT> stuff I've seen at some hamfests.  It was similar to the bags of
 RJT> resistors I had enountered a while back,  too.  And it's close to being
 RJT> a fairly generic assortment of parts,  too,  except for that 565 chip. 

Yes, that's the puzzler if that package was intended for one
particular project.

 RJT> And those zener diodes. Why 5.1v when there's no logic anywhere
 RJT> around? 

Why not? With a lot of jobs you need some kind of stable
reference. If you have TTL logic somewhere in the system, 5v is a
already there so you use it. If you want the same design in
another project that doesn't use TTL anywhere, using the same
voltage means you don't have to redesign.

 RJT> Yeah.  I still have a "709" or two around,  and maybe an
811 (which
 RJT> I'm sure nobody has ever heard of),  stuff like that.  They were
 RJT> actually considered superior to the 741 for some uses,  though I can't
 RJT> recall which uses those were offhand.

The big advantage with the 741 was that it was internally
compensated down to unity gain. The big DIS-advantage was that
this compensation limited the slew-rate to something like 0.5
volts per microsecond typical.

So if you wanted to swing the output to near full rail voltage,
that's a 30v swing on a +/-15 supply, you would run into
slew-rate limiting from about 8KHz up, maybe lower in chips with
worst case specs.

With the 709, all the compensation was external, so you would add
just enough to make it stable at whatever gain you were designing
the circuit for. So the slew rate could be typically ten times as
high for a gain of ten, and still keep it stable.

At least that's how I remember it.

 RJT> 500KHz?  Hm.  Not that much,  really,  though with all the tricks that
 RJT> get wrapped around PLL circuits that doesn't mean that it's not useful.

There aren't many integrated PLLs that work a lot higher. The
4046 only goes to 0.7MHz typically.

 RJT> What would you do with one of these?  :-)

One use is PLL synchronous detection from the 455KHz IF in an AM
receiver.

I haven't tried it myself, but they say the distortion can be at
least as low as that of an FM receiver.

And you get ZERO adjacent channel interference, which has always
been the bugbear of AM receivers.

From Greg Mayman, in beautiful Adelaide, South Australia
   "Queen City of The South"    34:55 S  138:36 E

... Having the fewest wants, I am nearest to the gods.
___ Blue Wave/386 v2.30

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