Swiss Army Knife vs Can Opener?

In my last entry I described a feature and option-laden filter/preamp board, comparing it to a Swiss Army Knife.  Great, but sometimes you just want a can opener…

After some serious discussion about how such a design would be used, and the typical requirements, I’ve decided that a major simplification is in order.  (And, of course, a new feature)

Filter-Preamp-simple v1

The consensus was that there was no need for bypassable filters, so the stages are now:

  • 18 dB shelf filter (-9 dB @ 6 MHz)
  • 17 dB preamp
  • 30 MHz elliptic low-pass filter (or 60 MHz as a different assembly)

This board is powered by an external +12V DC supply, and draws about 20 mA.  There is an active-filter stage that should clean up most supply noise.  The new feature is simple low-loss reverse-polarity protection for the power input.

Here is the (simulated) gain of this unit:

simpleAnd the schematic:

Simple Schematic

Actually, the two filters can be bypassed at assembly time as a load-option.  Perhaps this will let this board also be used as an amplifier-only design.

I have sent this design out for PCB fabrication and ordered the components — I can’t wait to see how it all comes together!


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