[time-nuts] KD2BD WWVB receiver/decoder in QEX
Charles Steinmetz
csteinmetz at yandex.com
Mon Nov 23 12:16:57 EST 2015
Paul wrote:
>post down conversion to 10 Khz I was scratching my head as to why not
>the TL08X series.
Input voltage noise. Unless you need the low input current of the
FET part, there is no need to take the noise hit. If you *do* need
the low input current, there are 4 or 5 generations of FET-input
opamps that are all far superior to the TL0xx parts. Take a look at
the OPA134/2134/4134, for example. (I haven't used TL0xx opamps
since the '70s.)
BTW: I suggested using NE5532s instead of LM387s and said they were
better in every way. Comparing the LM387 to the NE5532, one might
notice that the bandwidth spec of the 5532 is lower (10MHz) than that
of the 387 (15MHz). But what is important for most applications is
not the small-signal BW, it is the power BW (full-output BW), which
depends on the slew rate, not on the SSBW. The 5532's 9v/uS slew
rate supports a PBW of 140kHz, while the 387's PBW is only 75kHz (S/R
is not stated). (This tells us two things -- first, that the 387's
slew rate must be <5v/uS; and second, that the 387 has less phase
margin than the 5532.)
Best regards,
Charles
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