Printed Coil

[RoTali]

Hello,

I have a great problem with the design of an printed coil.
I want to design a 130nH coil on a PCB but I have
2 different Formulas to calculate the inductivity.
So I´m not really sure which formula I should use.
I hope somebody knows a solution for my problem.

Any advice would be greatly appreciated.

 

[melone]

Why would you want to create an inductor with traces? The precision of your "inductor" will vary based on the trace characteristics, i.e. thickness (or lack thereof). In your PCB construction, are you using only base copper, or are you plating to a desired level, i.e. 0.5oz plated to 1.0oz, or are you using 1.0oz copper. This can make a big difference since only one of these scenarios guarentees 1.0oz of copper at every instance of a trace / plane.

 

[Comcokid]

There are plenty formulas for PC inductors. Each inductor geometry will require a different formula. One good source is "Transmission Line Design Handbook" by B.C. Wadell, Artech House Publ, Chapter 6.

PC Inductors are frequently non-ideal. Due to the distributed parsitic capacitance and low-inductance-per-unit-length of trace, PC inductors have Q problems, and may try to act like a transmission line stub in your circuit. However, for cost savings reasons, PC inductors frequently show up in circuits, and some RF software programs allow you to model them. As Melone points out, tolerance repeatability is also a problem.

 

[RoTali]

Well, thanks for your answers I think that I will use
a normal Coil in a 0603 Package it´s smaller and
not so complicated.