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Bat Detector

Posted: Mon May 30, 2011 8:04 am
by jimmy101
Very interesting article, one that I might give a try.

Two points / questions though. In Figure 5 (Board Layout) it looks like there should be a cut in the Vero board trace underneath capacitor C4. Also, there is no connection to the battery negative. There should be a connection between the trace in the lower left corner and the trace to it's left?

Re: Bat Detector

Posted: Thu Jun 02, 2011 1:19 pm
by Michael Kaudze
This was sent to the author. Awaiting response..

Re: Bat Detector

Posted: Sat Jun 23, 2012 12:04 pm
by jimmy101
A few more comments on the circuit.

1. The quoted opamp gains are way off. At say 50KHz the maximium gain for the particular opamp is only 20x since the Gain Bandwidth product for that opamp is 1MHz. For the pair of opamps the maximum gain is therefore ~400. At DC the gain is unity.

2. The feedback circuits for both opamps probably should be designed specially for the ~30KHz-100KHz range. As drawn the maximum gain for the amp occurs at about 11KHz which would seem to be too low. I would think it would be better to redesign the two-pole filter to put a maximum gain at 40KHz-50KHz range and another up at 90KHz or so.

3. A nearly identical version of the circuit was published in "Everyday Practical Electronics" March 2004. ... vertor.pdf

See also my comments at ... 650#p79650
on possible simple extensions to use the same basic circuit to do both heterodyne and digital detection.