Hi there,

My question may be quite silly, but i wonder if there where any attempts to create high capacity variable capacitors.
Currently varicaps are basically diodes with very low capacity (pF to nF range).
I was wondering if creating a paper/aluminium prototype with a carbon mesh in between the electrode foils (the sandwich layout would be : isolator, electrode, dielectric, carbon mesh, dielectric, electrode, isolator) could disturb the capacity if an electrostatic potential was applied to the carbon mesh.
The use of carbon mesh fibers would allow some electrostatic buildup between the electrodes because of the holes in the mesh. a very thin mesh would be ideal (graphene ?).

Varying the potential applied to the mesh would change the capacity of the capacitor (if i understand coulomb law correctly)
The capacitor would have three terminals.

Am i completely wrong in the understanding of capacitors or is the idea worth pursuing ?

 

I have no idea if your physics is correct but I am intrigued by the idea.

Keep in mind that a varicap has a lot of requirements. Possibly the most important are leakage and equivalent series resistance.

If either of these is too large then the Q of a resonant circuit suffers.

 

Hi there,

My question may be quite silly, but i wonder if there where any attempts to create high capacity variable capacitors.
Currently varicaps are basically diodes with very low capacity (pF to nF range).
I was wondering if creating a paper/aluminium prototype with a carbon mesh in between the electrode foils (the sandwich layout would be : isolator, electrode, dielectric, carbon mesh, dielectric, electrode, isolator) could disturb the capacity if an electrostatic potential was applied to the carbon mesh.
The use of carbon mesh fibers would allow some electrostatic buildup between the electrodes because of the holes in the mesh. a very thin mesh would be ideal (graphene ?).

Varying the potential applied to the mesh would change the capacity of the capacitor (if i understand coulomb law correctly)
The capacitor would have three terminals.

Am i completely wrong in the understanding of capacitors or is the idea worth pursuing ?

Changing the potential on the mesh won't affect the capacitance unless it actually changes the dielectric properties. The effect of the mesh is to make a series parallel capacitor circuit.