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'[EE]: Re: Can a speaker be Input Devices'
2003\06\02@170645 by ?q?Debbie=20Hynes?=

--- Debbie Hynes <spam_OUTdebbiehynes2002TakeThisOuTspamYAHOO.COM.AU> wrote: >
Oops - sorry if this repeats. Put the [EE] tag in the header  ... :|

Sure, but impedance matching is the problem. U need to amplify a lot but since
the speaker's Z is usually 8 ohm, u need to use an 8 ohm/1K audio transformer
to step up the sig & impedance if feeding into a common emitter amplifier.
If u don't want to use a transformer, u can put the spkr in the emitter leg
(low Z) of a common base ampifier and match Z's & boost o/p sig that way.


> > Can a speaker act as input devices to an Voice Activation
> > circuit ?  I want to built a Voice Activation circuit without
> > using Mic. Is this possible ?
> >
> > Any voltage frustration from the speaker that can trigger a
> > transistor ?
> >
> > Thanks. - Yahoo! Mobile
- Check & compose your email via SMS on your Telstra or Vodafone mobile.

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