The buzzer may need an amplifier

[sarins]

I made this tiny device just now, I have replaced 1220 battery by rechargeable lion battery 3.7V, but the buzzer did not work, and the same time, I found the typical application circuit from manual of buzzer, I think the buzzer circuit missing a important part, which should be an amplifier, the ATTiny13 IO port can not supply enough current for the buzzer at all, so for following DIYer may need to caution for this issue.