Hello everybody,

I am an engineer at one of the electronics company at Delhi. I just wanted to know all the methods to reduce the stray capacitance. Also, if the stray capacitance isn't considered in the design, what will be the effect on the performance of the system.

Please reply stating all the information you have and oblige.

PARIN

 

Ok, this is a vast area. A single wire or conductor forms a capacitor with every other wire or other isopotetial surface in it's environment.

There are methods to reduce stray capacitance itself and others to reduce it's influence. Reducing stray capacitance means reduce one of the factors in capcitance calculation
C = A (area of capacitors) / distance * epsilon (dielectric constant).

So you may increase distance, use short wires, cables or PCB patches to minimize the area, use low epsilon dielectric materials for PCBs or cables. These are in principle all the methods to reduce stray capacitance.

The effects on system performance maybe two:
1st, signal rise and fall times become longer, because the signal source has to charge the capacitance threw it's output resistance.
2nd, capacitive coupling to and from other signal sources can cause malfunction distorting signals.

Here, measures to reduces the influence take in. The very first is electric shielding. The equivalent circuit of the unshielded situation is a (stray) capacitor between two signals, while with shielding there is a series connection of two capacitors (signal two shield and shield to other signal) paralleled with a much smaller cpacitor that is still signal to signal long as there is a direct pass for the electric field from conductor to conductor. For high frequencies, it becomes important, that the shield to ground connection is of low impedance (inductivity). Otherwise inductive resistance "insulates" the shield from ground. Imagine the shield as a "floating" electrode in the niddle of the capacitor. It would have no effect at all.

To reduce it's influence, you may

 

Stray capacitance where? and on which system ?
Meir

 

Mr. Thomas Hergenhahn (above) knows what he's talking about. You should also pay special attention to the length of leeds on the components in your circuit. Just a little after thought.