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Old 19th Apr 2021, 8:45 pm   #14
Radio Wrangler
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Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Default Re: Buffer Amplifier for Digital Frequency Counter

Another thing is that the second transistor is biassed from the first transistor's gate characteristic, which is notoriously uncertain from device to device, s oquiescent currents could be all over the shop. Something a bit more RFy than a 2N2222 would also be a good move and an easy swap. These super-simple bias schemes save a few resistors (which are easily visible) but often add the need to use selected transistors (which is invisible right until it doesn't work)

David
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