Binary transitions, power consumption

[phdshine]

I'm studying the ethernet devices and the transmission system over cable wire and I'm interested especially on the power consumpiot due to the binary transitions from 0 to 1 and viceversa in the transistors. It is possible to estimate how many WATTS (i thinks nW) are necessary to the device to switch from 0 to 1 or viceversa?
it is due to the charge and discharge of the cable parasitic capacitance?
thank you in advance

 

[berkeman]

I'm studying the ethernet devices and the transmission system over cable wire and I'm interested especially on the power consumpiot due to the binary transitions from 0 to 1 and viceversa in the transistors. It is possible to estimate how many WATTS (i thinks nW) are necessary to the device to switch from 0 to 1 or viceversa?
it is due to the charge and discharge of the cable parasitic capacitance?
thank you in advance

You are not driving the parasitic capacitance so much. You are driving into the characteristic impedance of the cable at high frequencies (Zo):

http://en.wikipedia.org/wiki/Characteristic_impedance

.

 

[Bob S]

Most coax cables range from 50 ohms (e.g., RG-8) to 125 ohms (e.g., RG-63) characteristic impedance Z_c. Z_c is the square root of the coax inductance per unit length divided by the capacitance per unit length. The parasitic capacitance cannot absorb energy (other than dielectric "tan theta" losses at GHz frequencies). The best cables for long distance signal transmission are Z_c~75 ohms with high signal velocity. The cable should be terminated in impedance Z_c to minimize reflections. The power losses are in the termination.

Bob S.