Connecting 8ohm Speaker Without Wasting Signal

[Inforfang]

Hi ...

I have Audio Frequency Signal and I want to Play the Signal on 8-ohm Speaker . i use this signal in one other circuit too . if I connect the Speaker Directly to the Signal , because of it's low resistance the signal gone !

I need the matching circuit to connect the speaker to . whitch have a High Input Impedance and low output Impedance . I don't need to amplify it . just connect it .

I want it least PARTs and ICs . one IC with no other components is very good .
I did the Voltage Follower of Opamp , but it didn't Work .

Any Suggestion ?

 

[FvM]

I don't need to amplify it . just connect it.

Current amplification, as required here, is also amplification. You have demonstrated the results of just connect it. A rich choice of integrated audio amps is available (you didn't tell about output power), most have a >1 gain and would need an input divider in your application.

 

[Inforfang]

I don't know the Output Power . It is a Little Speaker . Just Like in OLD Computers . (But Not a Buzzer)

What Audio Amp you suggest ?
and Why the Voltage Follower didn't Work ?

 

[rfmw]

Try LM386 it is simple enough **broken link removed**

 

[Audioguru]

An 8 ohm speaker needs a peak current of 375mA to produce an output of only 1/2W. An opamp has a max ouput current of only 20mA.

 

[Kral]

inforfang
Take a look at the TI OPA569.
https://focus.ti.com/lit/ds/symlink/opa569.pdf
Also, you could use a power MOSFET in a source follower configuration. This would give you a gain of 1. You would need to capacitively couple the output to the speaker, since you would have a DC offset on the output.
Regards,
Kral

 

[Audioguru]

The OPA569 has a max recommended supply voltage of only 5.5v. Then its output at clipping into an 8 ohm speaker is only 0.46W.

The package is a tiny surface mount type and its bottom must be soldered (somehow) to some copper as a heatsink.