Jerry Martes wrote:

"money" wrote in message
ps.com...
I have a circuit in which there is a series capacitance of value 680
pF. The characteristic impedance of the line is 50 ohms. Can any
suggest how do i plot the capacitance in the smith chart.

If suppoe it was a parallel capacitance, how do i do it?


Hi Money

A purely reactive load, plots on the circumference (or perimeter) of the
Smith Chart. It plots on the lower half (the minus impedance half) if it is
capacitive, as in your case.

If you pick a frequency around 10 MHz, the capacitor will have close to 75
ohms X sub C.
Since you are working with a 50 ohm line, 75 is plotted on the lower half
of the chart, at its perimeter and with a value of 75/50, or, 1.5 on the
chart.

I really like getting help thru Wikipedia. If you read a few of their
sites on "Smith Chart" and still have questions, I'd be happy to tell you
what little I know about Smith Charts.

Jerry


Yeah Jerry..... I have seen Wikipedia. :-) But from where did you get
75 ohms X sub C.... Wat does it mean?

Converting 680pF series capacitance to capacitive reactance we need to
use Xc = 1 / CW.... Is it not??