# transistor amplifier with the common emitter configuration

Discussion in 'Electronics Homework Help' started by malyrudy, Apr 15, 2014.

1. ### malyrudy

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0
Apr 15, 2014
Please help me people. In school we were given homework, suggest a scheme of "amplifier common emitter configuration" and I do not know how. The scheme I have found, I even tried to calculate, but the amplifier does not amplify. Please, if someone would not be willing to help me with this, suggest resistors R1, R2, Rc, Re. I measure the input gain and output gain. If the text was a problem, I apologize for my bad English.

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2. ### KrisBlueNZSadly passed away in 2015

8,393
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Nov 28, 2011
Hello and welcome to Electronics Point.

I have moved your post from the Circuit Help forum to the Electronics Homework Help forum.

1. Check the polarity of your supply voltage. Also, the supply voltage source is usually shown at the right hand side, not at the top like that.

2. Your resistor values are all far too low. R1 and R2 are generally somewhere in the range 10~100 kilohms. You will need to recalculate the other resistors as well.

3. ### malyrudy

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Apr 15, 2014
Thank you very much. Now it works. Now I would like to know how those values came from. I get it dialed system "trial and error" but I need to calculate them on paper black on white. :/

4. ### KrisBlueNZSadly passed away in 2015

8,393
1,271
Nov 28, 2011
There are various ways to calculate them, but a good place to start is to choose the collector current. A typical collector current for a small-signal amplifier is a few milliamps. If there's a need for low output impedance, a higher current can be used, and if there's a need for low current consumption (battery powered device), a lower current can be used, but otherwise, a few milliamps is good.

I've actually gone through the calculations and explanations on another thread. Have a look at