I’m using the diodes ?am as this is text book protection for opamps ? Can’t speak to FET’s or a >10M input impedance?
Best Regards,
Jules Ryckebusch?
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On Oct 5, 2024, at 16:04, Richard Lee via groups.io <ricardo_lee@...> wrote:
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Dunno about piezo amps @ about 10M but for a LN condensor mike over 1G, the diodes must have VERY low leakage.
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1n4148 far too leaky and noisy.? Guru Scott Wurcer liked a smoke alarm FET used as a diode.? Another 'diode' for this is the BE junction of an old fashioned LN BJT like BC214 or 2n5087.
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Schottkys have very poor leakage which gets worse with time.? The latest THAT 1510/12 datasheets for microphone preamps recommend cheapo 1n4003GP (Glass Passivated).? I've personal experience of Schottky protection diodes going noisy in several MOTU Travelers withing 12 mths and indeed all da MOTU designs cured by replacing with 1n4003
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Dunno if 1n4003 will protect Jule's piezo amps.
