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<span style="font-family: helvetica; font-size: 14pt;">It's probably the caps. Ceramic and mlcc caps are known to be microphonic. NP0 and C0G types supposedly are less so than regular ceramic caps.</span>
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<span style="font-family: helvetica; font-size: 14pt;">I'd just go with thru hole unless there is a size restriction. That way you can test and select the transistor.</span>
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<span style="font-family: helvetica; font-size: 14pt;">Good luck.</span>
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<span style="font-family: helvetica; font-size: 14pt;">Jay S</span>
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On 12/12/2025 9:55 PM PST Mike Beauchamp <<a href="mailto:list@mikebeauchamp.com">list@mikebeauchamp.com</a>> wrote:
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I'm noticing my latest batch of MMBT3904 by ONSEMI are barely creating
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any white noise, requiring about 8000x gain to get up to +/- 5V.
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Previous batches of the MMBT3904 only required about 500x gain to get up
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to +/- 5V. When I was using TH 2N3904, I think the gain required was
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only about 200x.
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This much gain is also making something on the board (ceramic caps, the
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transistor itself?) pretty microphonic and tapping on the board is now
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audible.
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Before I order a few dozen samples of different transistors off digikey
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to test, I'm wondering if anybody had any go-to parts for SMT
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transistors that are still noisy?
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Mike
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