On 08/10/2011 18:25, Peter Johansson wrote:
> What I am unsure about are PWM frequency and inductor selection.  200
> kHz seems an oft-referenced frequency in the analog designs, but it is

You don't need ANY inductors!

You can with 5V rail drive the 8 Ohm or 16 Ohm speaker direct. With one=20
FET it's unpolar so you only get 1/2 the cone travel.

200kHz is bad choice in UK/Ireland  as its 2KHz off R4LW, but "HiFi"=20
designs would use 170kHz to 1MHz range. Above 500kHz switching losses on=20
higher power designs are challenging. I'd avoid 220KHz to 270KHz too.

About 70KHz to 80KHz is fine. Even 20KHz will work for "telephone"=20
quality sound.
--=20
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