Hi all,

I got some wonderings concerning basic eletronic, but in some of the cases I think it's just a matter of not mastering the english. Anyway, since I don't know any better place to ask, here we go:

1.
What does "sink" mean? If "I sink a transistor" - it's base (can I say so?) will the amplifying koefficient be maximum?

What does also "to source" mean? "The parallel port can source [...]"

2.
A common term - "Pull up resistor". What does it mean and how does it work? Does it "pull up" the current to a certain level?

Probably on the topic:
If I put a "regular" LED on AT89S51's P0, will it "pull up" the current to the maximum current it can take, and then acting as a resistor? According to the electronic specs is looks like a bad idea to drive a led from the pins directly..(Am I right? Is a transistor the proper solution?)

3.
What's the difference between a voltage regulator and a "operation amplifier"(in Swedish: operations förstärkare)? Is the voltage regulater fixed and the OP. Amp. variable with the two resistors?

4.
What does "step up/down" mean regarding Voltage regulators?

5.
What's a "flyback connection"?



BTW.
Found this AN about PWM:
http://eportal.apexmicrotech.com/mainsite/...note30.pdf


It's quite alright if you point me to documentation, I guess this is basic..

Thanks for all the help,
Frans