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Old 20th Apr 2021, 11:42 pm   #21
Bazz4CQJ
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Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,923
Default Re: Buffer Amplifier for Digital Frequency Counter

This thread reminds me so much of a couple of threads dating back a few years ago to attempts to build hi-impedance RF millivoltmeters (see post #8 above).

Quite a number of designs for such had been published in magazines over a period of some time; I had built a couple and Skywave built quite a few I think, and none worked anywhere near as well as they were claimed to.

When forum members skilled in the use of LT spice, and having a good understanding of the workings of J-FET's got involved, the basic problems with the designs became apparent (the phenomenon of negative resistance in FETs being one factor). Quite how so many flawed designs had been built and tested, and then published, seemed hard to understand.

B
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