# Can voltage division be a applied to an electret microphone signal (around 40mV)?

#### abdulwahab.hajar

Joined Jun 14, 2016
93
I was designing a transistor amplifier to amplify the signal of an electret microphone, throughout my simulations though I assumed my input voltage would be around 10mV rms as that is what research had told me about the output of an electret microphone...
However, while testing I found out that the microphone outputs a signal in the range of 40mV rms......
and my amplification gets distorted....

Attached is both the distorted and un-distorted outputs...
I tried re-configuring the resistances but to no avail, even when I decrease the gain when the input is 40mV rms, I still get some distortion...
So I was thinking of dividing the input signal by series resistances, is it possible?
if not any suggestions would be gladly welcomed..

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#### ericgibbs

Joined Jan 29, 2010
16,389
hi ah,
What are the collector and emitter DC voltages, ie: without any input signal.?
E

EDIT:

this is one simple option.

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#### abdulwahab.hajar

Joined Jun 14, 2016
93
hi ah,
What are the collector and emitter DC voltages, ie: without any input signal.?
E
Yeah, Vce was 3.788V... thanks for noticing, I configured the biasing resistors to get a Vce of 6.16V to place it nearer to the center of biasing region... although it's better I still get distortion at an input of 40mV... any ideas?
I tried using your addition to the design, funny thing is... Multisim still shows me distortion.. are you using a 40mV input source?

Last edited:

#### ericgibbs

Joined Jan 29, 2010
16,389
hi,
This is the frequency response.
E

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#### abdulwahab.hajar

Joined Jun 14, 2016
93
hi,
This is the frequency response.
E
I'll try implementing it on circuit and see what happens... Thank you...
But regarding the basic question... does voltage division work?

#### ericgibbs

Joined Jan 29, 2010
16,389
hi,
You could use voltage division, to half the signal, but check the effect it may have on the overall frequency response.
E

#### abdulwahab.hajar

Joined Jun 14, 2016
93
hi,
You could use voltage division, to half the signal, but check the effect it may have on the overall frequency response.
E
Thank you

#### Bordodynov

Joined May 20, 2015
3,012
See

And it's even better to take a low-noise operational amplifier.

#### crutschow

Joined Mar 14, 2008
30,801
are you using a 40mV input source?
Eric used a 40mV peak signal or 28mVrms in his simulation.

#### ericgibbs

Joined Jan 29, 2010
16,389
hi Cark,
I did also precheck the circuit with a 60mVpk signal.
Eric

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#### KeithWalker

Joined Jul 10, 2017
2,522
I was designing a transistor amplifier to amplify the signal of an electret microphone, throughout my simulations though I assumed my input voltage would be around 10mV rms as that is what research had told me about the output of an electret microphone...
However, while testing I found out that the microphone outputs a signal in the range of 40mV rms......
and my amplification gets distorted....

Attached is both the distorted and un-distorted outputs...
I tried re-configuring the resistances but to no avail, even when I decrease the gain when the input is 40mV rms, I still get some distortion...
So I was thinking of dividing the input signal by series resistances, is it possible?
if not any suggestions would be gladly welcomed..
Change the collector load from 9 Kohms to 4 Kohms. That will change the no-signal collector voltage from 4.8 volts to 7 volts allowing the output at the collector to go + and - 5 volts without clipping.