# Transistors!

Discussion in 'General Electronics Discussion' started by SB0202022, Nov 7, 2012.

1. ### SB0202022

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Oct 27, 2010
So when I place a transistor in a circuit, just assume a VERY basic circuit as shown in the diagram, how do I determine how much this transistor is amplifying the signal in terms of voltage, such as how do I know if I place the transistor in that same place as the diagram shows, it could amplify the signal that much? Could someone either explain the math to me, or possibly direct me to a tutorial that could?

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2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,449
2,809
Jan 21, 2010
It's not amplifying voltage at all.

It's amplifying current.

And you can find a range of expected values for this gain in the datasheet. Look for HFE

3. ### SB0202022

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Oct 27, 2010
Thank you! And one last thing, in your opinion, what is a good starting project for a starting electrical engineer? Involving transistors of course, to gain a better understanding of them.

4. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,449
2,809
Jan 21, 2010
Understanding how they operate would be a good starting point.

As to whether you start from a theoretical basis, or from a practical one; it depends on whether you're a theoretical or a practical kinda guy.

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Mar 23, 2011
6. ### john monks

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Mar 9, 2012
I think a good thing to do is to think of some fun device such as a metronome or a theramine or a crystal controlled audio oscillator for tunig a guitar or piano. Just think of something you might want around the house. Try to draw up a schematic and see if it works. Or come up with an idea and post it on the forum and we can all have fun with it. You might look at some circuits in popular electronics, QST magazine, or the ARRL handbook and copy them.
I firmly believe that playing with circuits is essential to learning electronics.

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Aug 9, 2012