Choosing transistor quiescent current

[audioguru]

A dynamic microphone has a fairly low impedance of about 600 ohms. The input impedance of the preamp should be about 2k ohms for very low noise. The input impedance of your preamp is too high.

If the supply is 18V then you want a symmetrical output swing so the idle collector voltage of TR-2 should be about +9.5V and the emitter voltage should be about 1V. The collector and emitter currents are (18V - 9.5V)/15k= 567uA. Its base current is listed on its datasheet and is supplied by R2 which also provides collector current to TR-1.
You do the calculations for TR-1.

 

[vuong]

Please help me little :
I want to design 1 schematic have :
INPUT : Microphone about 600ohms
Use transistor C1815

Ecc : 9v

I choose Ucemin = 1v. (1)

I have Uce = Vcc-RcIc-ReIe (2)

(1),(2) > 8 = RcIc + IeRe

= beta*Ib*Rc + (beta+1)Ib*Re

= Ib( beta*Rc +(beta+1)*Re.

And what I should do now ?

Way 1 : choose Rc first

Way2 : choose Re first

Way3: choose Ib first (if choose Ib fist , how to calculate it ?)





I think : when have signal whe have schematic

I think : Zmicro = Zinput impedance :

But I don’t know how to choose beta in : Vo= -Beta*ib*Rc
Please help me calcualate this

 

[audioguru]

I was taught to never ever bias a transistor with a single resistor from the supply to its base because the beta of a transistor is a range of numbers, not a single number.

 

[vuong]

So can you teach me comple this schematic , please fix it for me ,,you can change some thing . this question 2 year ago but upto now i can't build 1 simple schematic , i studying university but no one help me do it

 

[audioguru]

So can you teach me comple this schematic , please fix it for me ,,you can change some thing . this question 2 year ago but upto now i can't build 1 simple schematic , i studying university but no one help me do it

It is a very simple amplifier. Ask your teacher to teach you how to design it.

 

[vuong]

I did, and i go to fourum electric VietNammese but no one help me , can you do it for me

 

[vuong]

Plzz , everyone help me alot , i readlly need your help