Hello!
i have tried for some time to get the right gain of this amplifiertransistor Circuit.
Im now trying to get help or a push in the right direction to let me solved this, there is probably something i have missed but i cant seem to figure it out.
I need to decide the gain of V(out)/V(g).
From the text (Swedish) i got:
hfe=B(ac)=300
(Ohm)
Rg=5k
RL=5k
Rc=2.7k
R1=68k
R2=15k
Re=100
RE=470
Vcc=10V
* i did take 1/hoe out of account because i cant solve for it and its most likely to big to take in account for the 4pole
First i got ICQ from (DC). IC=ICQ
By tumb rules of constructing a DC curcuit i take 45% of the VCC over RC = 45% of 10 = 4.5v
By ohm it gives me about 4.5/2.7k=1.7mA (I have also calculated this the long way and got 1.7mA)  it checks out.
With ICQ i can calculate gM. = Gm=ICQ/VT, i guess VT is aproxx 0.025v
by standars transistors. So:
1.7mA/0.025~=0.067 =gm
Now i can get hie=r(pi) by gm=hfe/hie
300/~0.067=4500 ohm.
To save time i write the final eqvation and how i use them: ( i used 4pol system to get this), also the equation
V(out)/V(g)=((Rin)/(Rin+Rg)) * (hfe*(RC))/(hie+Re(hfe+1)  Is know since before
V(out)/V(g)=((Rin)/(Rin+Rg)) * (hfe*(RC//RL))/(hie+Re(hfe+1).  Added RL (Load) in 4pole equation.
Rin = R1//R2//(hie+Re(hfe+1) this gives: ~9068.3 ohm
so:
V(out)/V(g)=~0.65*~15.2, this give me = ~ 9.88 gain.

Now i use voltage diver to calculate:
*equation shorten
(hfe*Rc//Rl)/(hie+Re(1+hfe)) = ~15.2
The voltage devider to take Rg in calculations
Rg/(Rg+Rx)*Vg=V(out)
Rx=(R1//R2)+Rg = ~ 17300 ohm
this gives: (since gain is absolut value so the negative don´t matter in this case, just for the signal)
Rg/(Rg+Rx)*Vg > ~0.22*vg=V(out)
Set voltage to 1v >
15.2*0.22 = 3.3 > so i remove 3.3 from 15.2 gain = 11.9 gain

The answer by the book is a gain on: 11.3.
If you want me to show more calculations/drawing i can post, but i hope this is enough to maybe help me see my error
i have tried for some time to get the right gain of this amplifiertransistor Circuit.
Im now trying to get help or a push in the right direction to let me solved this, there is probably something i have missed but i cant seem to figure it out.
I need to decide the gain of V(out)/V(g).
From the text (Swedish) i got:
hfe=B(ac)=300
(Ohm)
Rg=5k
RL=5k
Rc=2.7k
R1=68k
R2=15k
Re=100
RE=470
Vcc=10V
* i did take 1/hoe out of account because i cant solve for it and its most likely to big to take in account for the 4pole
First i got ICQ from (DC). IC=ICQ
By tumb rules of constructing a DC curcuit i take 45% of the VCC over RC = 45% of 10 = 4.5v
By ohm it gives me about 4.5/2.7k=1.7mA (I have also calculated this the long way and got 1.7mA)  it checks out.
With ICQ i can calculate gM. = Gm=ICQ/VT, i guess VT is aproxx 0.025v
by standars transistors. So:
1.7mA/0.025~=0.067 =gm
Now i can get hie=r(pi) by gm=hfe/hie
300/~0.067=4500 ohm.
To save time i write the final eqvation and how i use them: ( i used 4pol system to get this), also the equation
V(out)/V(g)=((Rin)/(Rin+Rg)) * (hfe*(RC))/(hie+Re(hfe+1)  Is know since before
V(out)/V(g)=((Rin)/(Rin+Rg)) * (hfe*(RC//RL))/(hie+Re(hfe+1).  Added RL (Load) in 4pole equation.
Rin = R1//R2//(hie+Re(hfe+1) this gives: ~9068.3 ohm
so:
V(out)/V(g)=~0.65*~15.2, this give me = ~ 9.88 gain.

Now i use voltage diver to calculate:
*equation shorten
(hfe*Rc//Rl)/(hie+Re(1+hfe)) = ~15.2
The voltage devider to take Rg in calculations
Rg/(Rg+Rx)*Vg=V(out)
Rx=(R1//R2)+Rg = ~ 17300 ohm
this gives: (since gain is absolut value so the negative don´t matter in this case, just for the signal)
Rg/(Rg+Rx)*Vg > ~0.22*vg=V(out)
Set voltage to 1v >
15.2*0.22 = 3.3 > so i remove 3.3 from 15.2 gain = 11.9 gain

The answer by the book is a gain on: 11.3.
If you want me to show more calculations/drawing i can post, but i hope this is enough to maybe help me see my error
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