LM386 Coupling Capacitor

[zero]

I'm building an audio amplifier using an LM386. According to its datasheet,
I should connect the LM386's output through a 220uF coupling capacitor to
the 8 ohm speaker.

If I use a 220uF polarized electrolytic capacitor (the only kind of
capacitor of this size at the local Radio Shack), should I connect the +
node to the LM386 output, and the - node to the speaker so it won't explode?

Also, will there be any problems with initially charging the capacitor when
power is first applied?

 

[Lord Garth]

"zero" <slave@discussions.com> wrote in message
news:kCjMd.101341$kq2.81210@twister.nyc.rr.com...

I'm building an audio amplifier using an LM386. According to its
datasheet,
I should connect the LM386's output through a 220uF coupling capacitor to
the 8 ohm speaker.

If I use a 220uF polarized electrolytic capacitor (the only kind of
capacitor of this size at the local Radio Shack), should I connect the +
node to the LM386 output, and the - node to the speaker so it won't
explode?

Also, will there be any problems with initially charging the capacitor
when
power is first applied?

The LM386 uses a single ended supply, +5 volts and ground for instance.
The answer to your question is in the datasheet located here:

http://www.national.com/ds/LM/LM386.pdf

Look at the typical applications on page 5...

 

[John Popelish]

zero wrote:

I'm building an audio amplifier using an LM386. According to its datasheet,
I should connect the LM386's output through a 220uF coupling capacitor to
the 8 ohm speaker.

If I use a 220uF polarized electrolytic capacitor (the only kind of
capacitor of this size at the local Radio Shack), should I connect the +
node to the LM386 output, and the - node to the speaker so it won't explode?

Also, will there be any problems with initially charging the capacitor when
power is first applied?

The 386 has internal bias resistors to set the average output voltage
at about half way between its positive and negative supply rails. If
the speaker connects between this node and the negative rail, then the
positive side of the capacitor goes to the amplifier.

There will be a brief pop from he speaker as the capacitor charges to
half the supply voltage. If this is bothersome, you can replace the
single capacitor with two 100 uf caps in series across the supply,
with the speaker connected between their junction and the output of
the amplifier. This puts half the supply voltage on the speaker.
--
John Popelish