thanks. So it works with a 1M input impedance.
How high input impedance can you do this before diode leakage
starts messing with the fet bias or lowering the input impedance?
BTW I have built the circuit I linked to and it works ok, but I'm
not sure if it sounds quite as good as without the diodes, nor how
much ESD protection I'm actually getting.
Which schottky diodes did you use? what current capability and
reverse voltage?
there's no point in protecting the fet only to blow the diode
which I fear could happen with the tiny 1N4148.
On 05/10/2024 21:01, Jules Ryckebusch
wrote:
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Yes!!! I just did this with my piezo buffer for my hydrophones.
You need Shottkey diodes. See this?
Best Regards,
Jules Ryckebusch?
?I hope this is OK to ask here as it isn't
exclusively a mic question but a general electronic question
that might be applicable to some mics.
Consider a fet input with a high impedance, that is
connected to a exposed bare wire or RCA type plug, because
it needs to be unplugged from the source.
This could be for a piezo pickup with an input impedance
of 5-10M or it could be for a condenser mic with an
impedance of 1G
Do I need to protect that bare fet gate from ESD it
might encounter in the world?
here's a schem to illustrate:
I have naively added diodes but I'm not sure if they
will actually lower the input impedance which obv I don't
want. The real-life behaviour of diodes at high impedances
is beyond my current level of understanding.
I'm also not sure if 1N4148 are big enough to offer much
protection.
Nor am I sure if R1 offers any protection.
Could any of the experts here talk me through what would
be wrong with the attempts at ESD protection in this
schematic?
