# What does audio amplification actually mean?

Discussion in 'General Electronics Chat' started by prabinmetals, Sep 11, 2013.

1. ### prabinmetals Thread Starter New Member

Jul 23, 2013
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0
As I know, current is flowing through my earphones that move the coil and create sound. So, does increasing the audio amplitude means magnifying that current? or voltage? or both? Both, because I know that speakers have wattage reading and P = IV. Should I try to get Pmax for max audio loudness?

So, when I say that I want to amplify a simple audio signal using common-emitter circuit, am I amplifying the current created by the audio signal?
Thanks!

2. ### #12 Expert

Nov 30, 2010
18,076
9,678
No. You are using the audio signal to control current that you added when you connected a transistor to a power supply.

For instance, if you transformer couple the audio signal, it is clear that none of the current in the original signal is flowing in the amplifier circuit. The output, however faithful to the original signal, is not composed of the same electrons.

Edit: Of course, I am being very literal. Was that the question you really wanted to ask?

Last edited: Sep 11, 2013
3. ### MrChips Moderator

Oct 2, 2009
18,194
5,715
Both.

Ohm's Law, I = V/R

If R is constant, then I increases with V. V increases with I.

Then it depends on R.
If R is small, you need a large I for the same amount of power P = I*I*R
If R is large, you need a large V for the same amount of power P = V*V/R

For example,
if you are using low impedance headphones, e.g. 4Ω, then you need large current, for example 0.5A x 2V will give you 1W output.

If you are using high impedance headphones, e.g. 600Ω, then you need large voltage, example, you need 24.5V x 41mA for 1W output.

Last edited: Sep 11, 2013
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4. ### Shagas Active Member

May 13, 2013
802
74
Common emmitter configuration amplifies both voltage and current . So there is power gain.

You are increasing amplitude which is Voltage .
You have a fixed impedance so by increasing voltage you are increasing current .(look at ohms law).
By increasing either voltage/current (decreasing impedance) you are increasing power which is VI .

Ehh probably not . You don't want to push your headphones or any speakers to their maximum loudness because you get an increase in distortion unless they are high end products.

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