I cite my research amp LTspice system.

Probably your curve is correct. I have found this in the datasheet:

Another way you can go about boosting an electret mic with a bipolar transistor; use the grounded base configuration.

Picture the classic textbook common emitter stage, both collector and emitter have a resistor to their respective supply rail, and the base is fed by a potential divider across the rails.

The bit that changes it from common emitter to common base, is simply moving the bypass capacitor from the emitter resistor to the lower resistor in the base divider.

The first thing to do is look up the recommended voltage for the electret capsule - its usually about 2V. The B/E junction will drop about 0.7V, so the voltage divider should be set to feed the base; 2.0V + 0.7V = 2.7V - now; simply replace the emitter resistor with the electret capsule.

If you can get hold of the exact right data sheet for your electret capsule, it should tell you the current for it, if not most are similar so any data sheet will give you somewhere in the right direction. If you can't get the spec for current, replace the collector resistor with a 100k pot and adjust for best operating point.

The common base configuration will give you plenty of voltage gain, but the current gain will be a tiny bit less than 1 - an emitter follower hung on the output will soon sort that out.

Have you ever done it? are you sure? can you post any schematic of all things about your idea?

 

Probably your curve is correct. I have found this in the datasheet:

Have you ever done it? are you sure? can you post any schematic of all things about your idea?

My project that I was working on at the time started off with a common base front end - then I discovered I could get more gain out of a TL431.

Look online for the textbook basic common emitter stage, then follow the steps I described.

 

I wired up this circuit(completely like this) on breadboard today and sounds like it's working very well:

But the output isn't enough loud(I connected a speaker at output and I think it's 8ohm. I'm trying to read the back of the speaker but it's not good clear to me. it's look like this:

).
Is it because of impedance matching?
Can we summarize this circuit? for example replace one resistor instead of R1 and R9 or summarize R2 & R3 and R5.
Can I use 3v3 for supply?

 

You could try to take C4 away and shorted the R9, listen to the quality of sound.

 

I wired up this circuit(completely like this) on breadboard today and sounds like it's working very well:

But the output isn't enough loud(I connected a speaker at output and I think it's 8ohm. I'm trying to read the back of the speaker but it's not good clear to me. it's look like this:

).
Is it because of impedance matching?
Can we summarize this circuit? for example replace one resistor instead of R1 and R9 or summarize R2 & R3 and R5.
Can I use 3v3 for supply?

R3 may be detrimental and should be removed.

When the DC nfb stabilises the operating point; the TL431 will have 2.5V on the in pin - this is close enough to what the electret capsule wants, that you can directly connect the capsule without coupling capacitor or separate bias resistor.

 

You could try to take C4 away and shorted the R9, listen to the quality of sound.

R3 may be detrimental and should be removed.

When the DC nfb stabilises the operating point; the TL431 will have 2.5V on the in pin - this is close enough to what the electret capsule wants, that you can directly connect the capsule without coupling capacitor or separate bias resistor.

Done but still output isn't enough loud.

 

Increase C2 some more and decrease R11, or using a 47Ω + 1K pot to replacing the R11.

 

To Vcc=3.3V.
You can use a low-voltage chip TLV431. Feature it is the same, but the reference voltage is about twice less (Vref~1.24V). Developer chip in datasheet provides the use of the amplifier circuit. It costs about a dollar.
You may need to replace the microphone. Your microphone should work at a voltage of 3.3V.
Also it may have to reduce the load resistor have a microphone (10kOhm). This will lead to a decrease in sensitivity to sound.

 

Increase C2 some more and decrease R11, or using a 47Ω + 1K pot to replacing the R11.

R9 and C4 and R3 is removed from the circuit.
C2 is replaced with a 220nf and R11 with 55Ohm + 1KOhm pot. apparently now the sound is loud but not clear. when I want to get an output(my circuit works), I have to get so close(in other word stick) to mic. maybe the problem is in biasing the mic.
How about to decrease R1?

To Vcc=3.3V.
You can use a low-voltage chip TLV431. Feature it is the same, but the reference voltage is about twice less (Vref~1.24V). Developer chip in datasheet provides the use of the amplifier circuit. It costs about a dollar.
You may need to replace the microphone. Your microphone should work at a voltage of 3.3V.
Also it may have to reduce the load resistor (10kOhm). This will lead to a decrease in sensitivity to sound.

Thanks.

 

...
Also it may have to reduce the load resistor have a microphone (10kOhm). This will lead to a decrease in sensitivity to sound.

Excuse me but this part of your remarks doesn't make sense to me.(I have underlined it)

 

→

R9 and C4 and R3 is removed from the circuit.
C2 is replaced with a 220nf and R11 with 55 Ohm + 1K Ohm pot. apparently now the sound is loud but not clear. when I want to get an output(my circuit works), I have to get so close(in other word stick) to mic. maybe the problem is in biasing the mic.
How about to decrease R1?

Thanks.

This one bjt amp has its limited, If the R11 is too small then it will leave the linear region and the sound will became bad, the resistor for mic to me is ok, but different capacitor mic has different characteristic, so you could try it, another easy thing to do is adding a totem pole, that is only an npn on upper side and a pnp on lower side, and the output of totem pole adding a 10uF to speaker.

You can adjust the R11 to get a good sound and adding the totem pole that it will be louder and the bjts pair you can use 2N2219/2N2905, 2N3053/2N4355 or 2SC1384/2SA684.

 

I just have these transistors in stock:

2N3906,2N3904,BC548,BC547,BC557,BC338,BC327,BC337,BF199

 

booboo said: Excuse me but this part of your remarks doesn't make sense to me.(I have underlined it)

For normal operation, the microphone must be a voltage drop on it not less than 1V. Otherwise, the internal transistor out of the amplifying mode. Microphone is DC current generator. The voltage drop across the resistor R1 is calculated by Ohm's law. The transmission coefficient is proportional to the load of the microphone.
I apologize for my bad English. I need to speak more simple phrases.

 

Try it use what you have.

 

For normal operation, the microphone must be a voltage drop on it not less than 1V. Otherwise, the internal transistor out of the amplifying mode. Microphone is DC current generator. The voltage drop across the resistor R1 is calculated by Ohm's law. The transmission coefficient is proportional to the load of the microphone.
I apologize for my bad English. I need to speak more simple phrases.

Ok, I got it. thanks. don't apologize and please go on. I like your posts.

Try it use what you have.

Then a 2N3904 for upper side and a 2N3906 for lower side should be ok. am I right? Is this ok?

 

Ok, I got it. thanks. don't apologize and please go on. I like your posts.

Then a 2N3904 for upper side and a 2N3906 for lower side should be ok. am I right? Is this ok?

You can try the circuit, but the 0.1uf(the output of 431) and R1 should take it away.
The easy one is to keep the original circuit and only adding 2N3904 and 2N3906 and 10uf ~47uF output capacitor.

 

You could try to take C4 away and shorted the R9, listen to the quality of sound.

All textbook examples for electret capsules show that bias decoupling arrangement - that part of the circuit is hyper-sensitive to noise on the supply rail.

A correctly set up TL431 will have 2.5V stabilised on the IN pin - the electret capsule would be very happy with that.

 

You can try the circuit, but the 0.1uf(the output of 431) and R1 should take it away...

Are you sure about R1? because currently I just have R1 to bias the mic. I have taken away R9 as I said already.

...The easy one is to keep the original circuit and only adding 2N3904 and 2N3906 and 10uf ~47uF output capacitor.

Without the Base biasing resistors of the transistors?

 

Are you sure about R1? because currently I just have R1 to bias the mic. I have taken away R9 as I said already.
Without the Base biasing resistors of the transistors?

Sorry, that is not R1, that is R11.

If you want to adding the circuit you found then the position of R11 will be replaced with R4 and D1.

 

All textbook examples for electret capsules show that bias decoupling arrangement - that part of the circuit is hyper-sensitive to noise on the supply rail.

A correctly set up TL431 will have 2.5V stabilised on the IN pin - the electret capsule would be very happy with that.

That's the TS want to reducing the parts, so if he care about the quality then he should keep that, sometimes the numbers of parts and quality of sound that you can't have both, when you change any components of TL431 then it could be affecting the output voltage, that's why I don't want to change the components of TL431, only adding some parts through the capacitor, so you can see the easy way I suggested.