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Future of BSS83? Alternatives?

Hello Folks,

Looking for a "wimpy" discrete n-channel FET for an adjustable phase shifter. The Philips BSS83 would be the ticket. This is not the Infineon BSS83PE which is p-channel and larger die. Although it hails from the early 90's it's still above 20c (ouch...) and it is on back order at a few places. Digikey still has a few thousand but these can be gone in one big slurp.

Do you guys think it might be on the way to lala-land or will it stay? A price that doesn't want to come down to jelly bean level always make me uneasy. Ok, this might be like asking for a weather forecast for May so let me also pose the question about alternatives. Are there some nice FETs in the 50-100ohm RDSon class? Preferable not any hot stuff such as the UHF dual-gate tetrodes and it doesn't have to have a separate pin for the substrate.

I used to do this stuff with SD5400 but these have become rather pricey and rare.

And Jim: No, I can't roll my own here...

Regards, Joerg

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Reply to
Joerg
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What? You can't use a CdS cell ?:-)

Or isn't there a 4000-series part with "loose" MOSFET's?

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.
Reply to
Jim Thompson

Hello Jim,

The 4007UB is a bit on the wimpy side but could work, in theory. A

74HCU04 would really be in the ballpark and could be used when driven between VCC/2 and one of the rails. However, both are too high in capacitance. I need something to the tune of 1pF so it looks really resistive. Else I'd be designing an involuntary resonant circuit since the inductor is just a fraction of a uH.

This is one of the situations where I'd rather be designing a chip for it.

Regards, Joerg

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Reply to
Joerg

Wonder if you couldn't take a 4016 or 4066 and float appropriate pins?

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.
Reply to
Jim Thompson

That should work. Tie enables to VDD, then vary VDD and VSS symmetrically to control Ron ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.
Reply to
Jim Thompson

Will a JFET do? Like a J310 or 2N4391? Digi-Key has a ton of xx4391's, and they're specified for RDSon. The J310 is a UHF amplifier transistor, so it shouldn't have severe capacitance issues.

Of course if you need to connect one terminal to ground and flop the other between 0V and 5V you'll need to stand on your head and use a P-channel, but there ought to be something similar.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google?  See http://cfaj.freeshell.org/google/
Reply to
Tim Wescott

Hello Tim,

Unfortunately it won't work since there is no negative voltage, usually.

It's basically about loading a delay circuit to shift the delay back and forth. The node to which the FET connects carries a fast clock and the FET acts as a variable resistor. Or let's say as a unidirectional load.

Regards, Joerg

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Reply to
Joerg

I assume a small Transfer Resistor won't work?

Reply to
Ian Stirling

"Joerg" a écrit dans le message de news:sJrPf.26739$ snipped-for-privacy@newssvr12.news.prodigy.com...

If it's a clock, you probably need controling one edge and don't mind the other.

I've just done this kind of thing that way:

Control | .-. | | | | '-' ___ | |\\ .-|___|--+-----+------| >O- Shifted | | |/__ | --- _// | --- | | | === | GND | Clock | ___ |\\ ----------+-|___|--+-----+------| >O- Ref | | |/__ .-. --- _// | | --- | | | '-' === | GND Vcc/2

Maybe you can adapt.

--
Thanks,
Fred.
Reply to
Fred Bartoli

The SD214 doesn't seem to as dead as I thought

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if you can buy it from Calalogic, and Linear Integrated Sytems - Sanken Electric does seem to have dropped out.

--
Bill Sloman, Nijmegen
Reply to
bill.sloman

a écrit dans le message de news: snipped-for-privacy@u72g2000cwu.googlegroups.com...

Vishay/Siliconix have all the SD21x too.

--
Thanks,
Fred.
Reply to
Fred Bartoli

Series R or R to ground?

If series R, common mode range?

I do believe a 4016 or 4066, control tied to VDD, vary VDD, will give a variable R.

It'll depend on how you're implementing the phase shifter.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.
Reply to
Jim Thompson
[snip]

Yep, it do work, at least in simulation.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

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| 1962 | It's what you learn, after you know it all, that counts.

Reply to
Jim Thompson

Hello Ian,

A gold-doped transistor would work but not as well. Things become very non-linear at the knee.

Regards, Joerg

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Reply to
Joerg

Hello Fred,

That will work. However, you have to accept shallower input to the upper buffer or inverter and that increases phase noise.

Regards, Joerg

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Reply to
Joerg

Hello Bill,

Also Vishay. But, Digikey doesn't carry it which is a warning sign. Arrow has no stock (also somewhat of a warning sign) and it is freaking expensive there, several Dollars a pop. 20c would be ok but not over a Dollar.

Regards, Joerg

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Reply to
Joerg

Hello Jim,

Series L.

VCC to GND would be the swing. Must work diff and non-diff.

Those have tons of capacitance. It would almost short out the signal. Clock rates would be 100MHz+. This is why the SD5400 would be nice if it were more popular and cheaper like it used to be.

Regards, Joerg

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Reply to
Joerg

Hello Jim,

Try it a 100MHz. Probably you'd have a week distorted sine wave coming out.

Regards, Joerg

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Reply to
Joerg

I only looked at resistance. The LVX version, the only type that I have true models for, varied from 10-25 ohms quite nicely.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

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| 1962 | It's what you learn, after you know it all, that counts.

Reply to
Jim Thompson

Hello Jim,

Thanks, I'll check the LVX version then since I have only dealt with the HC and CD varieties so far. It's all about capacitance in this scenario.

Regards, Joerg

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Reply to
Joerg

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