Timeline for Pull-up resistor over a microphone
Current License: CC BY-SA 3.0
12 events
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| Jul 9, 2018 at 21:32 | comment | added | endolith | This is incorrect. The bias voltage is not applied to the microphone diaphragm at all ("electret" means the diaphragm has a permanent electric charge). The bias voltage is used to power a built-in FET impedance converter, so this whole discussion about resistor values is irrelevant. | |
| Apr 6, 2012 at 9:28 | comment | added | Connor Wolf | Note: An electret microphone almost universally has a FET inside to amplify the change in voltage created by the movement of the plates. Electrets mics have a static charge applied to the plates, it's not a function of the bias voltage either. See the wikipedia page on electret microphones | |
| Apr 6, 2012 at 8:56 | comment | added | jippie | In this application you want current to be very small. This type of mic requires a charge on its plates and it gives the best results when this charge does not change over time. In that case the voltage across the microphone follows the movement of the plate. If you manage to keep the charge 'number of electrons in the plates' equal, then the voltage across the device varies with distance between the plates. | |
| Apr 6, 2012 at 8:52 | comment | added | clabacchio | The signal is basically a current because dQ=I, so to have big voltage given that V=RI you need big R | |
| Apr 6, 2012 at 8:46 | comment | added | user16307 | this is the point i dont get. if the resistor is 0.0001 ohm why signal is astronomically small? shouldnt it be opposite according to ohms law I=V/R. so i was thinking less resistance will cause higher current. where am i wrong? | |
| Apr 6, 2012 at 8:43 | comment | added | jippie | theoretically ... yes, but the signal you get from it will be astronomically small. In practice I'd go for 10k or 100k maybe even more. | |
| Apr 6, 2012 at 8:36 | comment | added | user16307 | so we can also use 1 ohm? same principle isnt it? no reason why 1 kilo ohm rather than 0.001 ohm? | |
| Apr 6, 2012 at 8:32 | comment | added | jippie | 1k is not very high, it is rather low. The idea is that the capacity of the mic does not discharge while its plates are moving. If you manage to keep the charge on its plates constant, then the output voltage follows the recorded sound in detail. The 1k resistor allows the capacitor to discharge rather fast, which will influence frequency response and output signal swing. The lower the series resistor, the lower the response for low frequencies. | |
| Apr 6, 2012 at 8:26 | history | edited | jippie | CC BY-SA 3.0 |
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| Apr 6, 2012 at 8:25 | comment | added | user16307 | thanks for ur answer but why it is too high like 1 kilo ohm | |
| Apr 6, 2012 at 8:21 | history | edited | jippie | CC BY-SA 3.0 |
added 37 characters in body
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| Apr 6, 2012 at 8:15 | history | answered | jippie | CC BY-SA 3.0 |