8ohms

[Powzoom]

I have an audio signal that's amplified by an op-amp. The output impedance of the op amp is around 100 ohm (is that right?) My speaker is 8ohms. How can I match this better?

 

[duffy]

You could look for a 500Ω:8Ω or maybe a 1K:8Ω impedance matching transformer -

- but don't expect too much. Opamps are not impressive speaker drivers.

 

[Willbe]

The output impedance of the op amp is around 100 ohm (is that right?)

Open loop. With closed loop it's virtually zero.

 

[Nigel Goodwin]

I have an audio signal that's amplified by an op-amp. The output impedance of the op amp is around 100 ohm (is that right?) My speaker is 8ohms. How can I match this better?

You add a power amplifier between the opamp and the speaker, an opamp isn't suitable for feeding a speaker.

 

[Hero999]

The impedance doesn't need to be matched. The amplifier needs to have a much lower output impedance than 8R which is why an op-amp isn't suitable for driving a speaker, as Nigel said.

 

[audioguru]

A puny half-Watt in an 8 ohm speaker is a peak current of 250mA.
But the max output current from an opamp is only 30mA. The output power at clipping into an 8 ohm speaker is only 0.004W.

The max output current from a little LM386 power amp IC is about 375mA. Then the output power in an 8 ohm speaker at clipping is 0.5W.

 

[crutschow]

Open loop. With closed loop it's virtually zero.

The op amp only has a low closed loop impedance until it's maximum current output limit is reached (generally a few 10's of milliamps) above which the closed loop feedback loses control and the output impedance becomes very high.

 

[mramos1]

If he wants to tell his friends he has a .004watt amp he made himself (for 1 speaker) And he will never get your point AG.

And the friends will not hear it unless putting thier ear right on the speaker and being a lot younger than me.

If this is a car or home audio project and you want more than the pets to hear it. Power AMP like Nigel said/read.

 

[audioguru]

If I said its output is 4mW then he might think 4 million Watts.

 

[Speakerguy]

Isn't that its PMPO rating?

 

[audioguru]

Isn't that its PMPO rating?

The LM386 amplifier with 0.5W output at clipping has an output of about 1000W PMPO.

PMPO is just a bunch of exaggerated lies.