SMT replacements for CEM

[Paul Schreiber]

Here are issues associated with what you are asking for.

1) size. You can't fit a 3340 equivalent in the same small size. I would
guess that
a double-sided hybrid that is like a 3340 would have to be about 1.5 x 1.5
inches.

This may or may not work synth-to-synth, due to mechanical interference of
surrounding parts
(electrolytic caps, etc).

2) cost. NOT going to be cheaper! On the most optimistic side, I'd say about
$45ea in 1000pcs.
OK that's $45,000 outlay.

3) performance. Curtis uses a patented gain gell OTA in all of the chips.
Love em' or hate 'em.
it's in there. The 3340s track so well because of the on-die thermal
matching of the transistors.
You CANNOT DUPLICATE this in discrete parts. You can do it "the
old-fashioned way" with either
heater circuits (blah!) or tempco techniques.

4) the 3310 VCADSR, #2 on the desired list, would need even a *larger* pcb.
The circuitry is not as
"critical" as in the VCO, but there are about 2.5X the number of parts
inside (the 3340 is a small
component count, much smaller than you think).

The "average" CEM chip has about 120 transistors and 40 resistors. Even
using 0805 resistors and
SOT-23 transistors, you have to allow for interconnect and transistor
matching. Pain in the ***.

Like I've said many times in the past: it is actually cheaper to pay OnChip
the $38,000 to remask/refab
the parts, because you end up with $2 CEMchips!!

Paul S.