general question on linear regulator

Hi guys,

I read somewhere that linear regulator can regulate output only if Vin is > vout. Is that true ?

Furthermore max efficiency is achieve when Vin is close to Vout. Does someone know how to evaluate efficiency and power dissipation? I plan to use max604 pdip package to regulate power for 328p chip is it a good idea ?

Bellow data sheet:

Thanks. BR

I read somewhere that linear regulator can regulate output only if Vin is > vout. Is that true ?

Yes.

Does someone know how to evaluate efficiency and power dissipation?

The difference between input and output voltage multiplied by the current drawn is the power wasted in regulating. This is dissipated as heat.

I plan to use max604 pdip package to regulate power for 328p chip is it a good idea ?

It's OK, but limited to 500mA.