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common emitter amplifier circuit using feedback biasing

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denian

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i don't have the basic of analog, but i tried to look for it in the books. unfortunately, the books are using voltage divider biasing instead of feedback biasing.

i have a circuit like this:

BJTampfeedbackbiase.jpg


would anyone tell me the flow of the current in the circuit, and made gain possible?
 

seadolphine2000

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In DC analysis, both (C1,C2) will be open circuited, thus the current passes through (Rc) will be divided into (Rb) and the transistor.

In AC analysis, the capacitors will be shout circuited, thus you can place the AC-model and decompose (Rb) by miller theorem.

The Voltage gain(Av) = -{Gm(Ro||RL||Rc||Rmi)}/{(Rmi||Rpi)/(Rmi||Rpi)+Rs}

Where: Rmi => miller input resistance.
Rmo => miller output resistance.
Ro => transistor output resistance.
Rpi => transistor resistance between base and emitter.

Hope this helps
 

denian

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tq, but your formula is hard for me to understand. i have no idea on what miller theorem is.

anyway, i've tried to do it in a conventional way.

Solution.JPG


but i realise it is wrong.
can anyone help clarify the method to count the gain?
 

tyassin

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Hi

You have one error. When calculating Vce. The corrrect expression is Vce=Vcc-Ic*Rc.

Regards
 

denian

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:cry:

actually im very confused.
this is actually a part of my pspice project.

in pspice, this is the graph i obtained.

gaingraph.jpg


how do you calculate it in using a conventional method to get gain value of 165?
can someone show me the calculations.
V1 will produce 1V a.c. voltage
 

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