Alan B Pearce wrote:
>>It acts like a fillter stops noise been fed through power and also as a
>>switch on choke.
>
>10 microhenries is not going to do much as a switch on choke. The arrangement
>pictured is used mostly to stop high frequency noise coupling through the
supply
>line The choke puts a significant impedance in the supply line, without having
>the voltage drop characteristics of a resistor of the same value as the high
>frequency impedance of the choke.
>

Kieran, to put a little more reality into the discussion, the
inductor acts similar to a large resistor at higher frequencies,
but a small resistor at DC. XL is inductive reactance [similar
to "impedance"]:

XL = 2*PI*f*L = 2*PI*1Mhz*10uH = 63 ohms @ 1 Mhz
[also 630 ohms @ 10 Mhz, ... - ie, more effective at higher freq]

The DC resistance of the inductor will only be in the 1 ohm range,
or so, so it wouldn't produce much IR drop in the Vcc line, but it
will help filter hi-frequency noise passing in "both" directions.
The combination of the inductor and capacitors on either side will
act like nice low-pass filters, although sometimes ringing and
other matters complicate the issue.