I have what seems like an easy question to answer however, I am tired of looking for the answer, so I will just ask it.
I have an Arduino Uno and want to take the already programmed chip that's on the Uno and place it on another PCB. Never take it off.
The question is:
What chip do I purchase to replace the one that went on the Uno? Do I have to get the AtMega328 with a bootloader or can I purchase the one without it?
ATMega328P-PU.
With or without, your call.
If without, there are myriad ways to reprogram it.
Such as: use the existing chip to program the new chip, put the new chip in your application.
If I were to get one without the bootloader can I place it on the Uno (without using the other chip) and upload a program to it? Once it's uploaded, can I then remove the chip and solder it to a PCB that is set to recieve the Atmega328 with the 16Mhz crystal and capacitors and have it work?
In order for a new chip to function on an Arduino board as an Arduino, it WILL need to have a bootloader.
It is a relatively simple task to put the bootloader onto a completely blank chip, especially if you already have an existing Arduino. You set up a relatively simple circuit with the new chip on a breadboard, and use your existing Arduino as a "device programmer" to burn the bootloader.