Ferrite beads/chips

Horses for courses. I use pots of beads, mostly the Murata BLM18BB ones, to stabilize microwave transistors in lower-frequency circuits. A

Beads have a unique combination of low noise at low frequency and higher, mostly resistive impedance at high frequency. The 5- and 10-ohm ones hold up as far as 3 GHz or more.

Cheers

Phil Hobbs

Signals. Miliamperes. Do you use 3A+ rated beads in those applications?

If not, then why do the damned things exist? The only purposes I can see are: a) to build nonlinear transmission lines, or b) to confuse anyone who doesn't realize they saturate at the drop of a hat.

Tim

But the garlic only works as long as you don't burn it. That's why you put it in towards the end of a sautee. As an engineer and cook, you know that.

Tim

Certainly. We cooked a big pot of beans today, a mix of red kidney and borlottis, with a little bacon and chicken-apple sausage and a ham hock, not too meaty. Cooked for about four hours. At the end, I shut off the heat and added the chopped garlic. I am *not* a barbarian.

"John Larkin" wrote in message news: snipped-for-privacy@4ax.com...

Today was leftovers, since I made extra stir-fry and brown rice the other day. Three habaneros....barbarians, what of them?

Tim

no DC bias but easier/faster to use than those LaPlace equation models.

The structure is almost identical to eddy current models.

• SIGNAL RF BEAD
• 0402 1k 100MHz Rdc= 1.1 ohm Idc= 250mA
• Murata BLM15HG102SN1 .SUBCKT RFBEAD1K 1 2 .PARAM Lfilter=6.8uH .PARAM Rfilter=1450 .PARAM C1=11 .PARAM C2=3 .PARAM C3=2 .PARAM C4=2 .PARAM C5=1 .PARAM CT={C1+C2+C3+C4+C5} .PARAM B1=1 .PARAM B2=7 .PARAM B3=8 .PARAM B4=11 .PARAM B5=15 RDC 1 3 1.1 L1 3 2 {Lfilter/B1} R1 3 4 {C1/CT*Rfilter} L2 4 2 {Lfilter/B2} R2 4 5 {C2/CT*Rfilter} L3 5 2 {Lfilter/B3} R3 5 6 {C3/CT*Rfilter} L4 6 2 {Lfilter/B4} R4 6 7 {C4/CT*Rfilter} L5 7 2 {Lfilter/B5} R5 7 2 {C5/CT*Rfilter} C1 1 9 0.027pF RLC1 9 8 200 LC1 8 2 55nH .ENDS RFBEAD1K
• PREFERRED POWER LINE FILTER RF BEAD
• 120 100MHz Rdc= 0.095 I= 1.5A
• Murata BLM15EG121SN1 .SUBCKT BLM15EG121SN1 1 2 .PARAM Lfilter=960nH .PARAM Rfilter=165 .PARAM C1=1.5 .PARAM C2=1.2 .PARAM C3=1 .PARAM C4=1 .PARAM C5=1 .PARAM CT={C1+C2+C3+C4+C5} .PARAM B1=1 .PARAM B2=1 .PARAM B3=2 .PARAM B4=2.5 .PARAM B5=3 RDC 1 3 0.095 L1 3 2 {Lfilter/B1} R1 3 4 {C1/CT*Rfilter} L2 4 2 {Lfilter/B2} R2 4 5 {C2/CT*Rfilter} L3 5 2 {Lfilter/B3} R3 5 6 {C3/CT*Rfilter} L4 6 2 {Lfilter/B4} R4 6 7 {C4/CT*Rfilter} L5 7 2 {Lfilter/B5} R5 7 2 {C5/CT*Rfilter} C1 1 9 0.12pF RLC1 9 8 171 LC1 8 2 3.nH .ENDS BLM15EG121SN1

• Murata 0603 BLM15EG221SN1
• 0402 220 100MHz Rdc=0.28 I= 700mA .SUBCKT BLM15EG221SN1 1 2 .PARAM Lfilter=1.8uH .PARAM Rfilter=270 .PARAM C1=5 .PARAM C2=3 .PARAM C3=2 .PARAM C4=2 .PARAM C5=1 .PARAM CT={C1+C2+C3+C4+C5} .PARAM B1=1 .PARAM B2=1.7 .PARAM B3=2 .PARAM B4=2 .PARAM B5=2 RDC 1 3 0.28 L1 3 2 {Lfilter/B1} R1 3 4 {C1/CT*Rfilter} L2 4 2 {Lfilter/B2} R2 4 5 {C2/CT*Rfilter} L3 5 2 {Lfilter/B3} R3 5 6 {C3/CT*Rfilter} L4 6 2 {Lfilter/B4} R4 6 7 {C4/CT*Rfilter} L5 7 2 {Lfilter/B5} R5 7 2 {C5/CT*Rfilter} C1 1 9 0.15pF RLC1 9 8 71 LC1 8 2 4.nH .ENDS BLM15EG221SN1

• POWER LINE FILTER RF BEAD
• Murata 0603 BLM18EG221SN1
• 220@100MHz Rdc=0.05 I=2A .SUBCKT RFBEAD220 1 2 .PARAM Lfilter=1.4uH .PARAM Rfilter=270 .PARAM C1=5 .PARAM C2=3 .PARAM C3=2 .PARAM C4=2 .PARAM C5=1 .PARAM CT={C1+C2+C3+C4+C5} .PARAM B1=1 .PARAM B2=1.7 .PARAM B3=2 .PARAM B4=2 .PARAM B5=2 RDC 1 3 0.05 L1 3 2 {Lfilter/B1} R1 3 4 {C1/CT*Rfilter} L2 4 2 {Lfilter/B2} R2 4 5 {C2/CT*Rfilter} L3 5 2 {Lfilter/B3} R3 5 6 {C3/CT*Rfilter} L4 6 2 {Lfilter/B4} R4 6 7 {C4/CT*Rfilter} L5 7 2 {Lfilter/B5} R5 7 2 {C5/CT*Rfilter} C1 1 9 0.15pF RLC1 9 8 71 LC1 8 2 4.nH .ENDS RFBEAD220

• 0603 60 100MHz Rdc= 0.1 ohm Idc= 500mA
• Murata BLM18PG600SN1 .SUBCKT RFBEAD060 1 2 .PARAM Lfilter=350nH .PARAM Rfilter=80 .PARAM C1=3 .PARAM C2=3 .PARAM C3=2 .PARAM C4=2 .PARAM C5=1 .PARAM CT={C1+C2+C3+C4+C5} .PARAM B1=1 .PARAM B2=1.3 .PARAM B3=2 .PARAM B4=2 .PARAM B5=2 RDC 1 3 0.1 L1 3 2 {Lfilter/B1} R1 3 4 {C1/CT*Rfilter} L2 4 2 {Lfilter/B2} R2 4 5 {C2/CT*Rfilter} L3 5 2 {Lfilter/B3} R3 5 6 {C3/CT*Rfilter} L4 6 2 {Lfilter/B4} R4 6 7 {C4/CT*Rfilter} L5 7 2 {Lfilter/B5} R5 7 2 {C5/CT*Rfilter} C1 1 9 0.5pF RLC1 9 8 31 LC1 8 2 4.nH .ENDS RFBEAD060

Where's the saturation?

Tim

-- Seven Transistor Labs Electrical Engineering Consultation Website:

How'd we get from beads to garlic..? I like to put some garlic in with the meat at the beginning too. (like when I'm browning ground beef for meat sauce (Bolognese)) The garlic gets in there and does something to the meat. Then more garlic at the end... and maybe add some in the middle too. What the heck, it's not like garlic is expensive.

George H.

no dc bias, I thought I said that. it's easy to add in LTspice, though, just had no need when I modeled these.

complaining about a 'free' model. GEESH!

Well, saturation needn't be a DC thing, but...

:-p I've got a saturable lossy core model kicking around somewhere, too. Easy to add -- of course. The hard part is finding the parameters though.

Tim

I made the cooking analogy... it kinda sorta makes sense, I guess?

Could also go with "don't burn the roux", kind of analogous again I suppose.

Last time I made pot roast, I shoved about a half a head's worth into the thing. Was damn good too.

Tim

My wife is half Italian, so she likes those cooked-to-death red sauces. I'm more of a white-sauce sort of guy.

The best white sauce is heavy cream and Regiano parmesan, maybe a little Una Kaas hard aged gouda. Bit of tarragon and pepper, dash of sherry maybe.

Needs more butter.

Best regards, Spehro Pefhany

People use even the higher ohm versions to above 10GHz. Sure, they are res istive-capacitive up there, but they still have some series impedance remai ning.

I usually use FB's (and most often 0402) in the sub 100 mA region.

--------------- The muRata BLM_P series claim to do a lot of current. (BLM41PG600SN1 claim s 6 A, for example.) But I wouldn't be surprised if they do saturate. Heck , they must by necessity. But how much? The manufacturer claims they are designed for such service. I did not note any info about impedance versus current from muRata. Hmmm... guess I better measure them. At least TDK ha s the info.

muRata catalog statement: BLM--P/S series - For Large Current BLM-P/S series can be used in high current circuits due to its low DC resistance. It can match power lines to a maximum of 6A DC.

I also found out early in my career that a meal heavy on the garlic tends to keep meetings short.

Have you guys ever tried the Pecorino from Costco? It's hard to stop eating.

As Phil said, you need to select the correct part for your application. For example, this ain't bad for a 1206-size part:

You still have 10ohms at 100MHz at the full 6 amps. Ferrite beads are not all that useful at 1MHz, they are meant to suppress radiated EMI and they do that quite well.

Also, one usually wants low Q in a bead. Except in the ones you buy for the girlfriend :-)

Maybe not so much for resonances between bypass caps and such that occur at lower frequencies, but also at lower impedances. But I wouldn't want to use a variable inductor for that anyway.

Probably won't do too much for, say, filtering switching noise out of a sensitive area. The zero bias curve would be fine for that, but since most manufacturers don't publish bias curves...

As for cable resonances, not much out of a, say, 50-200 ohm resonance. Enough to turn sharp spikes into dull peaks, which might get you passing, but it's hardly a good solution.

What if you don't have a way to test full load in the lab -- maybe it was designed for X peripherals that draw 1A, then later on, Y, Z and W are added on and now it's doing 6A? Or...you simply forget to test all the edge cases?

The smallest value I see is,

There's also these,

So, in size comparison, both of these are probably better than 2-5 FBs in series, which is still a layout win, assuming you need that much of course. Cost is comparable, though the IHLP one is on the pricey side even considering how many it would replace.

Tim

Good ones do.

Sure it works. The trick is to also have a small ceramic cap right where things leave the enclosure. Together with a 10ohms residual RF impedance in the bead that can easily knock down a nasty bunch of peaks by 20dB or more. I do a lot of EMC work.

If push comes to shove I don't have a problem schlepping a fat car battery into the lab. That can do 100A if needed.

Django never forget.

Yeah, but the ferrite is lossy and that's part of the game. Else EMI is like a water bed. You press here, goes down, only to come up at all the other spots.

Those inductors are for power converters, not EMC. And 86 cents is usually prohibitive for EMC measures.

But it's a power inductor, too expensive, and probably not lossy enough. You don't want to just reflect EMI back into the box. Then it would just leak out somewhere else.

How is a >10x higher cost comparable? Ferrite power beads are less than