printed inductors

sn't

perhaps it is a high frequency inductor which is more like a distributed transmission line inductor?

When it doubles back it'll reinforce the magnetic field, and only destructively interfere on the next line over (with the current going the same way).

But I have no clue how much difference it makes, or how much it acts like a straight wire of the same length.

The ones you see on PC boards may be delay lines. When you route a differential pair and turn a corner or something, one trace gets longer than the other. So some people wigwag the shorter one to make the electrical lengths equal.

Like this:

I doubt that a tight wigwag has a time delay that exactly corresponds to the geometric trace length that the PCB layout software reports.

Real RF inductors are usually proper spirals.

"Tim Wescott"

.... Phil

sn't

We make spiral coils on PCB to 'shim' magnetic fields. I'm not sure what you mean by zig-zagging back... maybe a picture?

Re: a coil versus a length of wire. You get more inductance from the coil. I think if you have a fixed length of wire and wanted to make the largest inductance then you'd wind it as one big single turn coil. (hopefully someone will correct me if that is wrong.)

George H.

George Herold Inscribed thus:

I suspect the OP is refering to the meander lines on a pcb used to match signal timing over varying trace lengths.

The only zig-zag inductors' I've seen, were tacho generators in "pancake" motors such as the spindle drive in a disk drive or similar.

Maybe a service manual for that kind of kit would throw some light.

PCB inductors appear to have poor Q. They are convenient to make, but lacking performance.

That is incorrect. Using same piece of wire, max. inductance is achieved with max. number of turns.

Vladimir Vassilevsky DSP and Mixed Signal Designs

I should have said that this definitely is an inductor. It's a choke connected to the power trace on a 4GHz board.

quare zigzag, each time it zags the trace doubles back on itself. Doesn't t his cancel the magnetic field to an extent? How much does the coil structur e matter to a coiled inductor, or would the straight wire have the same ind uctance? -- Reply in group, but if emailing remove the last word.

Look up Microchip application note AN710. It has a complete tutorial on the design and analysis of printed inductors (disguised as RFID antennas).

So what's the correct answer, oh brilliant one?

And have you taken your meds today?

Oh yeah, you can make a choke. You can think of it as an inductor, or as a long, lossy, high-impedance transmission line, which it is in the sense that it has some limiting Zo at high frequencies, and reflections. Chop out some ground plane to increase Zo.

I did a zigzag choke like that recently:

It maybe wasn't absolutely necessary, but I had the room and it was sort of fun.

Hey, engineers are easily amused.

If you know the operating frequency, you can optimize the length for max impedance. RF stuff.

How many channels? I saw a 40-channel NMR shim system once. It was hard to tune.

There is a solution for that somewhere. Turns out to be a stubby solenoid.

Yeah just DC coils.

the

ke

OK thanks... (of course I have to go and check it now... grumble)

George H.

sn't

the

o tune.

Hard to tune... I bet. This has just 4 coils, one each for the X, Y and Z gradient and then a Z^2 gradient. (Z is the diectron of the static field.)

OK I'll have to check... gotta run

George H

.highlandtechnology.com  jlarkin at highlandtechnology dot com

But is it wrong to call it an inductor?

Its operation depends on its magnetic field, so what is the effect of having each segment of conductor nearest to segments conducting in the opposite direction?

What he said. The meandering traces one sometimes sees are more delay lines than inductors. That square-section trace on a printed wiring board associated with a motor's ring magnet is a true inductor, but it's for flux coupling, rather than for high inductance value.

tune.

Optimal coil length is a bit less than the coil radius.

A Brooks coil is pretty close to optimal.

tune.

Good, now that that's settled, what form is best for maximum Q? Mikek