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)
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:
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!