HELP Single Stage BJT Common Emitter Amplifier resistor calc
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HELP Single Stage BJT Common Emitter Amplifier resistor calc

 
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NiCeBoY



Joined: 02 Sep 2008
Posts: 6
Posted: Tue Sep 02, 2008 10:54 am    Post subject: HELP Single Stage BJT Common Emitter Amplifier resistor calc Reply with quote
Hello.. can anyone help me out to calculate the value of resistors R1, R2, Rc and RE please?

The values should be such as the out gain is between 10dB to 20dB

The transistor used in this circuit is bc547 and the load resistor is a fixed one of 10k.
Below is the circuit:



Thanks

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neon



Joined: 25 Feb 2006
Posts: 611
Posted: Thu Sep 04, 2008 11:41 am    Post subject: Reply with quote
Well you cannot ever get a gain of 10 out your circuit. why not make work with a a LM124 family of amplifiers. then you may adjust gain with a potentiometer to what you want.. anyhow your collector R is to small and the emiter is too large. also input is .5v x1.41=.75v peak x A=10 it will saturate at anyhow.
solution you must first define the input and the output otherwise it becomes wishfull idea. for now try R1=20KR2=20K RE=100 RE=1K. BUT STILL WILL SATURATE AT HI INPUT.POINT 3 GETS + POINT 6 GETS + ON THE CAPS
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NiCeBoY



Joined: 02 Sep 2008
Posts: 6
Posted: Fri Sep 05, 2008 3:40 am    Post subject: Reply with quote
Its a project man...
i should use the transistor bc547B..
and Vcc should be 15V
and the load resistor Rl should be 10k..

These values are fixed.. i should only adjust the resistors..

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neon



Joined: 25 Feb 2006
Posts: 611
Posted: Sat Sep 06, 2008 4:04 pm    Post subject: Reply with quote
Man i don't do school works.You must solve it.There is if you ever want to learn at all.
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NiCeBoY



Joined: 02 Sep 2008
Posts: 6
Posted: Sun Sep 07, 2008 5:32 am    Post subject: Reply with quote
Hello,
Finally i calculated these values for R1 & R2 & Rc & RE...

Now the problem i am getting is that my calculated values and measured values is not the same..
Here is my circuit :



Using Beta = 110 as on the datasheet :
and also using approximate analysis..
My calculated values are as follows:

Vb=1.597V
Vce= 5.13V
Ic~=IE=0.897mA
Vc=6.03V
Ib=8.08 micro.Amps
Input inpedance = 4791.96 Ohms
Output impedance = 5000 Ohms
Vo=4.44V

Can anyone check my circuit and let me know if its in good working condition?

Thanks in advance...
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neon



Joined: 25 Feb 2006
Posts: 611
Posted: Sun Sep 07, 2008 7:15 am    Post subject: Reply with quote
You finaly got the hang of it. 1.597 vdc ok as bias means ~1ma on emitter or 1v /1k=1ma 1ma on rc=10vor 5vce max gain `3.5 have fun.
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neon



Joined: 25 Feb 2006
Posts: 611
Posted: Sun Sep 07, 2008 7:16 am    Post subject: Reply with quote
neon wrote:
I MUST DO SOLVE IT? Not realy You finaly got the hang of it. 1.597 vdc ok as bias means ~1ma on emitter or 1v /1k=1ma 1ma on rc=10vor 5vce max gain `3.5 have fun.
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