# Hi, I'm stucking into BJT Amp.

Discussion in 'Homework Help' started by Shoken, May 23, 2014.

1. ### Shoken Thread Starter New Member

May 19, 2014
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0
Hi guys,
I didn't learn about BJT Amp. yet, but my professor just assigned project.
There's 2 things to do.

Make a 1 step amplifier circuit to amplify each 1Vp-p with 1KHz frequency & 10mVp-p voltage with 1KHz frequency to Maximum voltage without distortion. Load register is 1KΩ.

What I want to know is how to solve this probelm...
What I have to study? and how can I ditermine each values at a circuit?

Until now, in my opinion, I used common emitter circuit like pics.

Thanks all.

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2. ### AnalogKid AAC Fanatic!

Aug 1, 2013
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First, lets make sure the problem translated correctly. By one setp amplifier I assume you mean a single stage amplifier. That is, an amplifier with one transistor. Correct?

If so, then are the 1 Vpp and 10 mVpp both input voltages, or is 10 mV the input and 1 V the output?

ak

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3. ### Alec_t AAC Fanatic!

Sep 17, 2013
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What is the supply voltage for the amplifier?

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4. ### Shoken Thread Starter New Member

May 19, 2014
3
0
Yeah, I meant single stage amplifier.
Also the 1 Vpp and 10 mVpp are both input voltages. So There's 2 thing to do.
In that case, How can I make a circuit with specific values. I wonder each values, and what is the relation of each values??

5. ### Shoken Thread Starter New Member

May 19, 2014
3
0
Supply voltage?? 12 DC voltage is supply voltage I think.
Is there problem??

6. ### shteii01 AAC Fanatic!

Feb 19, 2010
4,522
717
From datasheet the maximum gain of 2N2222 is 300.
So.
If you have 300+ volts power supply, you can input 1 Vp-p and get out 300 Vp-p.

If you input 10 mVp-p (0.010 Vp-p), you get out 3000 mVp-p (3 Vp-p).

I think those are the maximum.

7. ### Jony130 AAC Fanatic!

Feb 17, 2009
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What? Where you have read that the voltage gain of 2N2222 is 300 ?

8. ### shteii01 AAC Fanatic!

Feb 19, 2010
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717
My textbook uses 2N2222 for just about all the BJT material, so the datasheet for 2N2222 is in the Appendix of my textbook. The Gain of 300 is the maximum gain.

The OP mentioned that they are supposed find maximum voltage without distortion. So I am using maximum value of the gain.

The OP said that they have not studied BJT amplifiers. Which tells me that we are not dealing with actual BJT Amplifier design, but something more simple.

Basically we are given input values, good. We are told to find maximum output values (I assume maximum output). The OP schematic uses 2N2222 BJT, we have access to 2N2222 datasheet. That is how I got my numbers.

If I am wrong, then OP have done a pees poor job of presenting the problem.

9. ### Jony130 AAC Fanatic!

Feb 17, 2009
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You are very wrong. Firs for +300V power supply, it is impossible to get 300V peak to peak at the output you you need 600V at least. Also it is not true that the maximum voltage gain is 300V/V for 2N2222. Can you give me the name of this book and the page where I can find this 300.
And are you sure you're not talking about the current gain ? Ic/Ib = beta = Hfe??

10. ### shteii01 AAC Fanatic!

Feb 19, 2010
4,522
717
You are right. I made mistake. Or better yet, I think, I made a series of mistakes.

I was talking about hFE. But I have read the section on BJT amplifier and I now know what I did wrong.

Interestingly... The section on BJT amplifier in my textbook has the example problem where DC condition is setup and then AC amplification factor (Av) is determined. Kinda, it seems to me, what OP is supposed to do... But they have not studied BJT amplifiers so... I think OP is not being truthful with us.