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common emitter amplifier

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marinara27

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hi everyone..

can someone explain to me about common emitter amplifier..


 

The important things that you should know in common emitter amplifier is:

*input wave=output wave

*Vce(voltage between common and emitter)= 2 Vcc

*The frequency response are two : for low freq and high freq
for low freq the formula is Gain=Rc/RE

for high freq the formula is Gain=Rc/(RE+re)
Rc(resistance in common)
RE(resistance in emitter)
re(resistance in Emmit on transistor)

*Capacitor value in emitter make a shift in frequency response in to the right
Higher its value, so the frequency cut off higher to
Its happen because capacitor slide over the high frequency so the high frequency doesn't through the RE.

I things that's enough

Andi
:D
 

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    marinara27

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andi21 said:
The important things that you should know in common emitter amplifier is:

*input wave=output wave

*Vce(voltage between common and emitter)= 2 Vcc
Click to expand...

Input wave = -output wave; the amplifier inverts.

Vce cannot be 2 Vcc. You probably meant Vcc/2. However, Vce depends on other parameters and is not something you would try to fix at a proportion of Vcc.

Keith
 

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    marinara27

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thank you so much IanP,andi21 and keith...
your information really help me...

can anyone explain to me about the circuit that i post just now..i get it from book.. it circuit of power amplifier class B.. i also include the waveform..
can any1 explain to me why is it it not amplify?
huhu..sorry..really need help in this power amplifier term..help me please..

 

andi21 said:
The important things that you should know in common emitter amplifier is:

*input wave=output wave

*Vce(voltage between common and emitter)= 2 Vcc

*The frequency response are two : for low freq and high freq
for low freq the formula is Gain=Rc/RE

for high freq the formula is Gain=Rc/(RE+re)
Rc(resistance in common)
RE(resistance in emitter)
re(resistance in Emmit on transistor)

*Capacitor value in emitter make a shift in frequency response in to the right
Higher its value, so the frequency cut off higher to
Its happen because capacitor slide over the high frequency so the high frequency doesn't through the RE.

I things that's enough

Andi
:D
Click to expand...

Ohh Andi.....
I am afraid you have to improve your understanding of transistor stages.
Practically, everything you wrote is not correct! Neither VCE nor the gain nor the role of the capacitor.
Please, answer similar questions only if you are really sure to be right.
 

Someone else must be reading the same book! That same circuit has been the subject of a discussion on here over the last few days.

Keith
 

i think the tutorial than IanP link to me already enough for me to gain my understanding of common emitter..really appreciate for your correction LvW and keith.... :)
 

Someone else must be reading the same book!
Click to expand...
But the poster apparently doesn't read other threads.:cry:

Oh, I see, it's simply a cross post.
 

thanxs for your concern FvM.. really appreciate it..
 

I see, that you understood it as invitation to start another cross posting thread...

However, I revisited your above push-pull-circuit and found, that it's working acceptable, if you actually connect the bias network.
I also increased the bias resistors by a factor of ten to reduce the bias current to a reasonable amount, but it doesn't affect the
waveform considerably. Please notice, that PSPICE is able of producing correct sine waveforms, if you adjust the transient analysis timestep.

As mentioned before, the voltage gain is below unity, but only by small percentage.
 

However, I revisited your above push-pull-circuit and found, that it's working acceptable, if you actually connect the bias network.


i do not understand the meaning "connect the bias network".. can u explain to me..so sorry...
 

Look sharp to see what is missing.

91_1270063073.gif
 

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