Chpt 6 - class b audio amp - help

Thread Starter

Alexander Dumas

Joined Oct 16, 2007
Hi... I came across your site / example for building a class b audio amplifier.

I don't have (6) 6v batteries... Can I use a single 12v battery? If so, can you tell me what modifications i would have to make to have it work?

I am particularly interested in this circuit because I bought a cheap head-phone FM radio and want to output the audio through this amp...

Lastly, it the output noticeable (e.g., loud) - or just so-so...


Joined Apr 27, 2007
You can use a 12V battery and a LM7806 voltage regulator. Apart from a 0.1uF tantalum capacitor at the output (as recommended in the datasheet), you don't need to use more components.

Thread Starter

Alexander Dumas

Joined Oct 16, 2007
Ok... But just to clarrify - why the voltage regulator?

I initially put (+) to 8, (+) to 5, and (-) to 4... Is that right?

Lastly, I am particularly concerned if the output will be LOUD - easily heard across the room - right?

If not, how do I boost the output?


Joined May 16, 2005
Pin 5 of the chip, the non-inverting i/p of amp B, must be connected to ground, not +. Ground is established by the voltage regulator.

It would, of course, be easier to use two batteries as suggested in the text.