how much power do the earphone need?

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nickooeda

Joined: 15 Sep 2004
Posts: 44
Helped: 2

25 Oct 2004 8:48 how much power do the earphone need?

I am going to design a PA for earphone,but i don't know the power that earphone need. Embarassed

by the way,what is the mean of impedance of earphone? that is AC impedance or other meaning??
thanks a lot!! Embarassed

vfone

Joined: 10 Oct 2001
Posts: 2327
Helped: 326

25 Oct 2004 13:04 Re: how much power do the earphone need?

Earphone usually needs 100mW of power.
Standard impedance for handset earphone is 32 ohms.

nickooeda

Joined: 15 Sep 2004
Posts: 44
Helped: 2

26 Oct 2004 2:41 how much power do the earphone need?

thank u ,vfone. I have anohter question, 32 ohms is the result test at 1khz ?? and 100mw is the max of the min power?? thanks

selvaraja

Joined: 01 Jun 2004
Posts: 224
Helped: 3

26 Oct 2004 6:33 Re: how much power do the earphone need?

that is should be maximum power transfer to load but should consider losses in the filters too

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vfone

Joined: 10 Oct 2001
Posts: 2327
Helped: 326

26 Oct 2004 8:41 Re: how much power do the earphone need?

The max power is 100mW. But from a PA point of view I think is good to have a little bit more margin (less distortions), and anyway this power is adjustable.
Impedance is tested somewhere between 1 and 3kHz, but the frequency response usually is between 100Hz and 15kHz.

nickooeda

Joined: 15 Sep 2004
Posts: 44
Helped: 2

27 Oct 2004 11:01 how much power do the earphone need?

thanks a lot to vfone and selvaraja
ok,impedance will change with the frequency.32 ohm is constant??I think the max power for headphone or earphone is different.if 3.3v supply,how can i calculate the current (rms) from supply??? Smile

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vfone

Joined: 10 Oct 2001
Posts: 2327
Helped: 326

27 Oct 2004 12:25 Re: how much power do the earphone need?

As I said, you measure the impedance only at one frequency (let's say 1kHz).
The power standard is independent from the power supply voltage (3V, 3.3V, 3.6V, etc). Of course, if you design for 100mW @ 3V, increasing the Vcc you will get more power.
For RMS current calculation this link may help you:
http://www.astro-med.com/knowledge/rmspower.html