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Q&A How does JFET biasing work in a 2-terminal electret condenser microphone?

I’m trying to understand the biasing of a 2-terminal electret condenser microphone.  The inner workings of a 2-terminal electret microphone are always drawn without a resistor at the JFET source.  ...

2 answers  ·  posted 7d ago by misk94555‭  ·  last activity 6d ago by Andy aka‭

Question JFET microphone bias
#2: Post edited by user avatar Nick Alexeev‭ · 2024-10-25T15:44:17Z (7 days ago)
new tags added
  • I’m trying to understand the biasing of a 2-terminal electret condenser microphone.  The inner workings of a 2-terminal electret microphone are always drawn without a resistor at the JFET source.  Is it supposed to be biased like a JFET in a self-bias configuration?  If so, how would that work without a source resistor?  Or, is there a source resistor and it’s omitted from diagrams for brevity?
  • ![2-terminal electret condenser microphone](https://electrical.codidact.com/uploads/j6hqggir6v0mw3u9y87nnxio0v2x) (from [here](https://diymics.com/how-to-use-electret-condenser-microphones/#the-basic-ecm-operating-circuit) )
  • ![JFET in a self-biased configuration](https://electrical.codidact.com/uploads/m5c4mcctr4kkkmboh2uuajfpf5o9) (adapted from [here](https://eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Semiconductor_Devices_-_Theory_and_Application_(Fiore)/10%3A_Junction_Field_Effect_Transistors_(JFETs)/10.4%3A_JFET_Biasing), same in [pdf](https://batch.libretexts.org/print/url=https://eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Semiconductor_Devices_-_Theory_and_Application_(Fiore)/10%3A_Junction_Field_Effect_Transistors_(JFETs)/10.4%3A_JFET_Biasing.pdf))
  • For context, the microphone which I’d like to use is Knowles EK-23133-C36.  It’s a 3-terminal electret mic.  I’d like to wire it in a 2-terminal (common-source) configuration, because I read that 2-terminal configuration is more sensitive at low sound pressure level.
  • ![table entry with EK-23133-C36 parameters](https://electrical.codidact.com/uploads/3msl9mk2yc6bmo059dwgr0g9aun9)(table on page 9 [here](https://media.digikey.com/pdf/Data%20Sheets/Knowles%20Acoustics%20PDFs/Acoustic%20Design%20Guide%202010.pdf#page=9) )
  • I’m trying to understand the biasing of a 2-terminal electret condenser microphone.  The inner workings of a 2-terminal electret microphone are always drawn without a resistor at the JFET source.  Is it supposed to be biased like a JFET in a self-bias configuration?  If so, how would that work without a source resistor?  Or, is there a source resistor and it’s omitted from diagrams for brevity?
  • ![2-terminal electret condenser microphone](https://electrical.codidact.com/uploads/j6hqggir6v0mw3u9y87nnxio0v2x) (from [here](https://diymics.com/how-to-use-electret-condenser-microphones/#the-basic-ecm-operating-circuit) )
  • general scheme for a JFET in a self-biased configuration (adapted from [here](https://eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Semiconductor_Devices_-_Theory_and_Application_(Fiore)/10%3A_Junction_Field_Effect_Transistors_(JFETs)/10.4%3A_JFET_Biasing), same in [pdf](https://batch.libretexts.org/print/url=https://eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Semiconductor_Devices_-_Theory_and_Application_(Fiore)/10%3A_Junction_Field_Effect_Transistors_(JFETs)/10.4%3A_JFET_Biasing.pdf)):
  • ![JFET in a self-biased configuration](https://electrical.codidact.com/uploads/m5c4mcctr4kkkmboh2uuajfpf5o9)
  • For context, the microphone which I’d like to use is Knowles EK-23133-C36.  It’s a 3-terminal electret mic.  I’d like to wire it in a 2-terminal (common-source) configuration, because I've read that 2-terminal configuration is more sensitive at low sound pressure level.
  • ![table entry with EK-23133-C36 parameters](https://electrical.codidact.com/uploads/3msl9mk2yc6bmo059dwgr0g9aun9)(table on page 9 [here](https://media.digikey.com/pdf/Data%20Sheets/Knowles%20Acoustics%20PDFs/Acoustic%20Design%20Guide%202010.pdf#page=9) )
#1: Initial revision by user avatar misk94555‭ · 2024-10-24T19:29:36Z (7 days ago)
How does JFET biasing work in a 2-terminal electret condenser microphone?
I’m trying to understand the biasing of a 2-terminal electret condenser microphone.  The inner workings of a 2-terminal electret microphone are always drawn without a resistor at the JFET source.  Is it supposed to be biased like a JFET in a self-bias configuration?  If so, how would that work without a source resistor?  Or, is there a source resistor and it’s omitted from diagrams for brevity?

![2-terminal electret condenser microphone](https://electrical.codidact.com/uploads/j6hqggir6v0mw3u9y87nnxio0v2x) (from [here](https://diymics.com/how-to-use-electret-condenser-microphones/#the-basic-ecm-operating-circuit) )

![JFET in a self-biased configuration](https://electrical.codidact.com/uploads/m5c4mcctr4kkkmboh2uuajfpf5o9) (adapted from [here](https://eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Semiconductor_Devices_-_Theory_and_Application_(Fiore)/10%3A_Junction_Field_Effect_Transistors_(JFETs)/10.4%3A_JFET_Biasing), same in [pdf](https://batch.libretexts.org/print/url=https://eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Semiconductor_Devices_-_Theory_and_Application_(Fiore)/10%3A_Junction_Field_Effect_Transistors_(JFETs)/10.4%3A_JFET_Biasing.pdf))

For context, the microphone which I’d like to use is Knowles EK-23133-C36.  It’s a 3-terminal electret mic.  I’d like to wire it in a 2-terminal (common-source) configuration, because I read that 2-terminal configuration is more sensitive at low sound pressure level.

![table entry with EK-23133-C36 parameters](https://electrical.codidact.com/uploads/3msl9mk2yc6bmo059dwgr0g9aun9)(table on page 9 [here](https://media.digikey.com/pdf/Data%20Sheets/Knowles%20Acoustics%20PDFs/Acoustic%20Design%20Guide%202010.pdf#page=9) )