Driving a small speaker with an H-bridge?

[S. Petrukhin]

and those optos are not only high resistance, they are also slow as molasses

Optos are not required, it is not related.

[langwadt]

and those optos are not only high resistance, they are also slow as molasses

Optos are not required, it is not related.

then why did you suggest it? https://www.eevblog.com/forum/beginners/driving-a-small-speaker-with-an-h-bridge/msg5312593/#msg5312593

[S. Petrukhin]

then why did you suggest it? https://www.eevblog.com/forum/beginners/driving-a-small-speaker-with-an-h-bridge/msg5312593/#msg5312593

One of the options... Opto is easier to control in the upper arm.

[ebastler]

a step-up will only increase the problem of high resistance switches

and those optos are not only high resistance, they are also slow as molasses

Thanks for pointing out the speed issue; that's another reason to avoid optocouplers. I don't see why one would use them in a 3.7 V system. And I don't see the point in transformers either for driving a small low-impedance speaker.

I will try the small H bridge (DRV8212), which I would consider the most elegant solution. But will also order a small integrated class D amp with internal PWM generation (PAM8302) as a fallback; maybe the dual-PWM beat frequency I am concerned about is not an issue in practice. And I do have a few small class AB amplifier ICs around -- they definitely work, but get less power to the speaker than I would like.

Thanks again to all who have provided advice!

[LinuxHata]

I guess, something like LTC1157 can be used for that task, but price....

[JustMeHere]

This amp is probably overkill for your application, (and you will need a boost converter somewhere) but maybe you can find one out there that fits our needs.  Takes PWM directly.

https://www.ti.com/product/TAS5103