How to calculate the headphone amplifer

Dear All:
If we get the specific of headphone amplifier , How do we calculate it ?
ex : 25mW into 16 0hm from 3.3V?
How do we design the last stage of power mos ?
Thanks a lot.

学习一下

输出级用class-AB吧

Can anyone share some thoughts?

Assuming single-end output:
P=U_rms^2/R ===> U_rms^2=0.025*16=0.4W==> U_rms=0.6235V ==> U_amp=1.1247V
if output DC=1.65V, the output amplitude is reasonable.
Maybe use a tranditional Class-AB architecture is OK.
Happy New Year！