Why are we using voltage followers?

Hi,
I have some small ques for u...

why are we using voltage followers?
is it for impedance matching or for something else?
If itz for imp-mat...then the next ques i was asked is(in an interview)
"when u dont know the source impedance how can u match impedance for maximum power transfer...

i know that 'they' provide high input impedance...
The next ques was..
"If my source can source infinity curent...will u prefer to use the
same high input impedance amplifier(ie voltage follwer(op-amp))?

Please give me the answers....

Re: Voltage follower

followers are used to adjust impedance input and output.
I used them for that purpose.

Re: Voltage follower

the use of voltage follower is to prevent the circuit from loading effect....

Re: Voltage follower

Well actually the main purpose of voltage follower is NOT impedance matching....rather it acts as a VOLTAGE BUFFER..


Whenever you want to take a voltage output, you want the output resistance to be as low as possible, so that more loading (i.e. drawing more current) will not cause some of the voltage to drop on the output resistance of the last stage of whatever circuit u are using....

Rather, when take a voltage output...we want to be sure, that the output voltage will vary very little as the load varies.....this is where a VOLTAGE BUFFER comes in....it has a very little output resistance and almost unity voltage gain...

Thus, for example if your last stage was previously based on some configuration which has a large o/p resistance....you add a VOLTAGE BUFFER at this o/p....the final o/p will have almost the same voltage as the previous stage, however now there will be a minimum loading effect!

Re: Voltage follower

Also think about it as a level shifter