[Beginers OPAMP question]

Can anyone explain to me the function of an op-amp in a simple manner ?
Especially this IC > LM358N
http://rocky.digikey.com/WebLib/ST%20Micro/Web%20Data/LM158_258_358_A.pdf

[0-30 Vdc Stabilized Power Supply]

Here is a pic also of the pcb file

[0-30 Vdc Stabilized Power Supply]

Hey Audioguru i made in 3 days time the original circuit in Express PCB.
Anyone has got the skills to make it match with the modified parts ??

PSU_0-30V_0-3A.zip

[Free sample chips!]

I have requested some parts from NT. At first my 1st mail at hotmail required that i pay because they had too many req from that email provider. After that i put my other mail, but someone after 2 days reported that they couldn't give me samples.
ANd all these because i am wrote no company i just put student..
I had requested 5 X 3914LM.

[0-30 Vdc Stabilized Power Supply]

Hi all 1st post here
And to start quickly here are some questions...
1) On post #93 someone asked about higher Voltage rating Caps can be used (change a 50V to a 250V) but he went to sleep :P
So is it possible ? The voltage rating of caps refers to how quickly does the Cap releases its energy ?
2) IS there an updated PCB image yet ?
3) In a previous post you audioguru say
"Our project doesn't specify a part number for D6"
But i see on the project page that says D6=1N4148
In the end shall we use the BZY79C5V6 you suggest ?
Or you did a typo, and you meant changing D7 and D8 ??