Hi every body ,

i build this circuit to have voltage gain =40
but i donot know if it is true or not .

http://www.mediafire.com/?ezkjznazhze

 

Rasha.
U need to define the output
Is it multisim you are using?

Next try to print the file to PDF and attach it to ur post

 

ya .. this is multisim program .
and this pdf file for my homework
http://www.mediafire.com/?zt25ikyzzn5

 

Hello,

It would be nicer to have the PDF uploaded to the forum.
This way it will be preserved for later viewers.

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Bertus

 

I copied it and cropped it but I could not remove all the Multisim chicken-pox dots. Then I converted it to a normal PNG file type and attached it here instead of at some other website.

It seems to be a video amplifier using the very old 2N2219 transistors.
The values of its base bias resistors are much too high. The values of its collector and emitter resistors are very low so that its high frequency response is good.

 

I copied it and cropped it but I could not remove all the Multisim chicken-pox dots. Then I converted it to a normal PNG file type and attached it here instead of at some other website.

It seems to be a video amplifier using the very old 2N2219 transistors.
The values of its base bias resistors are much too high. The values of its collector and emitter resistors are very low so that its high frequency response is good.

do you think it is correct?

 

do you think it is correct?

No, it is wrong.
Didn't you read what I said about it? "The values of its base bias resistors are much too high."

Why does it use very old video transistors?
Why are the values of its collector and emitter resistors very low?
Why are the values of its base bias resistors much too high?
Did you learn about how to bias a transistor?

Didn't you simulate the circuit?

 

As you have drawn the schematics. You should be able to simulate it. A simulation will tell you if it work or not. We can not do this for you. But I know many members use the same software as you do. And are free to ask questions regarding how to simulate in this forum

 

A simulation will test only "typical" transistors.
But since the values of the base bias resistors are much too high then the transistor currents will change with the wide range of current gain from individual transistors. Then the circuit might not work. The transistors are almost cutoff anyway.

The values of the base bias resistors should be corrected.

 

brothers i simulat it by oscilloscope but no asuitable signal appear i did that at the midnight yesterday i really was tired . so i will build anther design , really i have alot of homeworks . i try to design QMS system that uses in bank for castumer by using MPLAB program . it take all my time .

thanks alot i try agian ...

 

Hi every body i did my homework chech the attachement to see the the circuit and analysis .
note:
channel A is for output signal, and Channel B is for input signal

 

Congratulation with your achievement

 

The voltage gain is only 12. It that enough?
The output level is very low and since the biasing of the transistors is not correct then the circuit might clip asymetrically with a higher signal level.
Q3 is doing nothing in the circuit and can be removed.

 

The voltage gain is only 12. It that enough?
The output level is very low and since the biasing of the transistors is not correct then the circuit might clip asymetrically with a higher signal level.
Q3 is doing nothing in the circuit and can be removed.

no voltage gain is 37.5

Av=((1.5*500m)/(4*5m))=37.5

stage 3 is the common collecter i use it to reduce the gain from 60 voltage gain to have 40 voltage gain

 

If you take the data at cursor T1 I got a gain equal to about 44.7

 

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Hey Rasha . not bad for a beginner
Congrats

 

Hey Rasha . not bad for a beginner
Congrats

ya.. thanks alot my brother

 

I still think your gain calculation is somewhat off. Because the gain is Vout/Vin or in this case Ch_A/Ch_B So if you at time equal to 409.593 ms have 411.308 mV at Ch_A and 9.192 mV at CH_B your gain will be 44.7. At least according to the simulations. Perhaps the gain value in a real circuit will be somewhere between your I guess calculated 37.5 and the simulated 44.7

 

We are all wrong.
the 'scope trace shows 500mV per division and 4 divisions p-p for the output. Its input is 5mV per division and shows 1.5 divisions.
Then the gain is 200/7.5= 26.7 times.

Transistor Q3 is supposed to be a buffer with no voltage loss, not an attenuator.

Transistor Q2 has an extremely high collector to emitter current (why?) but the current in the R5/R6 divider for its base current is too low.