Hi, I'm wondering how this circuit works. I understand that this is an electret microphone and the electret capsule (think J-fet) is what is amplifying the signal. What I don't understand is why there is a 0.1uF cap between the drain of the j-fet (or MC1) and the source ...or MICE (MICrophone Earth...I'm guessing....which is the LNA ground....I think). Wouldn't this provide a very low impedance to ground, filtering out the very signal we are trying to generate??? See PDF attached.

Cheers.

 

apx. ::

 

Hi ci139. Thanks for your reply. I'm interesetd in the role of C10 0.1uF. It's the same value as the dc blocking capacitor of the MIC signal C3. So C10 is by-passing the generated audio signal straight to ground (MICE being the ground of the pre-amp). When you say linearizer/ integrator what do you mean? Couldn't integrate my way out of a wet paper bag in high school. To me it seems to attenuate the signal in a big way. Why would we want to do that??

I got to wonder if the value for C3 (0.1uF) is correct. It makes a high pass filter with R4 (2K2) with a cut off frequency of 750Hz. That seems to be too high for voice. ? Perhaps Its a typo and is actually 1uF??

 

I got to wonder if the value for C3 (0.1uF) is correct. It makes a high pass filter with R4 (2K2) with a cut off frequency of 750Hz. That seems to be too high for voice. ? Perhaps Its a typo and is actually 1uF??

Wrong direction. As the shunt element of a filter, a smaller capacitor will extend the audio passband to lower frequencies. 0.1 nF makes more sense.

ak

 

When you say linearizer/ integrator what do you mean?

the integrator for this particular case means that it acts as "integrating op amp" -or- the testPoint in an " InputSignal--R--TestPoint--C--GND "
/// the integral is defined as a sum← ← of differential values -- if you see ← ←this as an ongoing process in time .. and the electrons as the "values" then the "SUM" -- a charge at C -- is added up/down by in coming / out going electrons . . . about Section 4.6 Numerical Integration The Trapezoidal Rule @ www.yumpu.com

the linearizer means that fast spikes and transitions get somewhat shunted+smoothed -- so the "fractal"/"rough" signal gets more linear/continuous