Originally Posted by theEgO

hello..
im doing a pc osc project. was wondering wat is the analogue circuit's main purpose for. ?? i saw aschematics which connects the input signal to the analogue circuit to a PIC chip. izzit to protect the PIC chip??

Generally it's to give gain, and provide a high input impedance (which is important with a scope) - it also provides a low impedance source to drive the A2D in the PIC, this is very important if you want fast sampling rates.