lm386 replacement with reduced part count?

Hi Stephen,

You're pretty much at the limit, you won't shave more than a couple of parts max. You'll need one or two resistors to set the gain on other devices (since there is unlikely to be an off-the-shelf part for such a gain value), a supply decoupling capacitor, and then input and output DC blocking capacitors. You could check out On Semi's 'NOCAP' range e.g. NCP2811A which is for headphones but would work with speakers too, which dispenses with the input and output capacitors, saving cost, but in return needs capacitors for generating a negative supply (but these are generally cheaper and smaller capacitors than that required for the input and output capacitor), but the max recommended voltage gain is 10 for it, although it might go higher - possibly worth a try).

Note that for a toy that makes beeps and tones, you might be able to use smaller capacitors with the LM386, since you're probably not looking for output near 20Hz. For example, 22uF instead of 100uF if you need response from a few hundred Hz, and a 32 ohm speaker instead.

I used the LM4808 SOIC-8, which is a stereo chip (I just used one channel), and everything fits in less than 2x1cm. This is still hand-solderable, and I wasn't going for the smallest size. There are smaller parts too.

It also can operate at low voltages so I can use (say) 10V rated capacitors instead of 16V, again saving on size.

EDIT: just noticed your input is PWM.. in that case you could see if you can get away with just a single transistor and a base resistor, and a 64 ohm speaker (run it from a low voltage, e.g. 3.3V). It won't be great but maybe good enough for a toy.

Hi Stephen,

You're pretty much at the limit, you won't shave more than a couple of parts max. You'll need one or two resistors to set the gain on other devices (since there is unlikely to be an off-the-shelf part for such a gain value), a supply decoupling capacitor, and then input and output DC blocking capacitors. You could check out On Semi's 'NOCAP' range e.g. NCP2811A which is for headphones but would work with speakers too, which dispenses with the input and output capacitors, saving cost, but in return needs capacitors for generating a negative supply (but these are generally cheaper and smaller capacitors than that required for the input and output capacitor), but the max recommended voltage gain is 10 for it, although it might go higher - possibly worth a try).

Note that for a toy that makes beeps and tones, you might be able to use smaller capacitors with the LM386, since you're probably not looking for output near 20Hz. For example, 22uF instead of 100uF if you need response from a few hundred Hz, and a 32 ohm speaker instead.

I used the LM4808 SOIC-8, which is a stereo chip (I just used one channel), and everything fits in less than 2x1cm. This is still hand-solderable, and I wasn't going for the smallest size. There are smaller parts too.

It also can operate at low voltages so I can use (say) 10V rated capacitors instead of 16V, again saving on size.

EDIT: just noticed your input is PWM.. in that case you could see if you can get away with just a single transistor and a base resistor, and a 64 ohm speaker (run it from a low voltage, e.g. 3.3V). It won't be great but maybe good enough for a toy.

Thanks.  I don't understand why these large capacitors are necessary, there are toys that make sound effects and there are no electrolytic capacitors at all, just one tiny IC and a few SMD capacitors.  For instance DIY talking greeting card devices that cost $1.50 total that record over 1 minute of sound and play it back and have flashing LEDs.  Do you happen to know what technology would enable these types of devices?

Thanks,

Stephen

The 'NOCAP' circuit is just the IC and a few tiny SMD capacitors, in fact just two capacitors and a supply decoupling capacitor, all SMD, all tiny, plus a couple of gain setting resistors per channel.