L
Lily Bepant
Guest
Hello,
I have been up to a question like this:
"Design a common emitter amplifier with an output impedance of 4.7Kohm
and a gain of -10 using 2N3904 powered by 12V DC power supply."
I got the pencil and paper started to design the thing. (I'm not an
electronics major)
I have jumped through many equations to find that: (I'm novice, so
don't assume that these are correct, please correct wherever possible)
Rc+Re=Vbb/Ic(max)
Ic(max).. I looked up 2N3904 manual and found that Ic(max) is 200 mA
for it. With 12V Vbb, it means Rc+Re= 60 Ohms. We want a gain of 10,
thus Rc/Re should be 10, which yields to the result that Re = 60/11 =
5.4 ohms Rc = 55 ohms (rounded these).
These values seem to be weird to me. What am I doing wrong?
Also, what would I take B (beta) of this thing? This is a design
question, therefore I understand that I should design something
independent of the B (beta) value. But how, when
R1+R2 = [(Vbb)]/[(10Ic)/B]
or not?
I'm interested in electronics but don't have enough knowledge on it.
Thanks for your guidance.
Best Regards,
Lily
I have been up to a question like this:
"Design a common emitter amplifier with an output impedance of 4.7Kohm
and a gain of -10 using 2N3904 powered by 12V DC power supply."
I got the pencil and paper started to design the thing. (I'm not an
electronics major)
I have jumped through many equations to find that: (I'm novice, so
don't assume that these are correct, please correct wherever possible)
Rc+Re=Vbb/Ic(max)
Ic(max).. I looked up 2N3904 manual and found that Ic(max) is 200 mA
for it. With 12V Vbb, it means Rc+Re= 60 Ohms. We want a gain of 10,
thus Rc/Re should be 10, which yields to the result that Re = 60/11 =
5.4 ohms Rc = 55 ohms (rounded these).
These values seem to be weird to me. What am I doing wrong?
Also, what would I take B (beta) of this thing? This is a design
question, therefore I understand that I should design something
independent of the B (beta) value. But how, when
R1+R2 = [(Vbb)]/[(10Ic)/B]
or not?
I'm interested in electronics but don't have enough knowledge on it.
Thanks for your guidance.
Best Regards,
Lily