Help with understanding blueprint

Dotted lines usually mean that a component is optional or only needed in certain applications.  For example, it may be that with a high gain you need a capacitor from pin 7 to ground for stability.  I don't know for sure when you'd need it -- I'm mostly a digital guy.

Hi Hunter,

I looked over the data sheet and they aren't very clear on pin 7 of the LM 386. I believe your answer is in the last part of the Paragraph on page 3 titled Input Biasing. They recommend putting in a 0.1 uF cap from pin 7 to ground on the higher gain configurations. The dotted line usually indicates that it is an option as opposed to a requirement. I hope this helps. You could set up your circuit and try it with and without the cap from #7 to ground.

John

The '386 has quite a high voltage gain, so if you've got long wires then there is a possibility things could become unstable, which you'll know about because you'll hear a loud squeal.

The capacitor on pin 7 (and a capacitor across the supply rails) is good to have nearby the LM386 to make sure it is getting a stable supply that doesn't change as the LM386 is

supplying current to the load (speaker).

A high voltage gain is undesirable if you're connecting the LM386 to (say) a Line output from a music system, because it already has a quite high voltage output, but is excellent if

you're doing experiments connecting the LM386 to a microphone for example. You can choose if you want a high or a low gain by selecting one of the example circuits in the datasheet.

As John mentions, there is no harm trying the circuit with and without the capacitor, and seeing the effects. It won't damage anything.

The '386 is quite a popular chip, you'll have fun experimenting with it. By the way, you might want to look at some beginners books to get started in electronics, it will accelerate your learning.

Thank you for your help!

Thanks for looking more into the datasheet for me! Your help is appreciated.

Your help is appreciated!