signal pickoff

[John Larkin]

I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0


The IC that I want to drive will be about a 2 pF load, and that wrecks
the 50 ohm microstrip transmission line that connects the two SMAs.
The idea is that a user can input a signal and either loop it into
another (several?) boxes, or screw on a terminator.

The 2 pF makes really bad stuff happen around 2 GHz or so, for the
loop-through path, and I'd like to go to 5. What I need is a
zero-capacitance buffer.

A phemt source follower might work, with a SAV551 or one of the
Skyworks parts. But fast source followers are also known as
oscillators.

Maybe I could use a series resistor into a 50 ohm MMIC amplifier. I'd
lose some signal but at least wouldn't have the horrible resonances
that a lumped capacitor makes.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Winfield Hill]

John Larkin wrote...

I'm daydreaming a new product, and this is one problem:
https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0

The 2 pF makes really bad stuff happen ...

You have passive choices: Reduce the 2pF to 0.5pF
by making a 1:4 divider, you can make up for the
loss later if required. Add resistance in series.



--
Thanks,
- Win

 

[Lasse Langwadt Christense]

søndag den 5. maj 2019 kl. 17.39.09 UTC+2 skrev John Larkin:

I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0


The IC that I want to drive will be about a 2 pF load, and that wrecks
the 50 ohm microstrip transmission line that connects the two SMAs.
The idea is that a user can input a signal and either loop it into
another (several?) boxes, or screw on a terminator.

The 2 pF makes really bad stuff happen around 2 GHz or so, for the
loop-through path, and I'd like to go to 5. What I need is a
zero-capacitance buffer.

A phemt source follower might work, with a SAV551 or one of the
Skyworks parts. But fast source followers are also known as
oscillators.

Maybe I could use a series resistor into a 50 ohm MMIC amplifier. I'd
lose some signal but at least wouldn't have the horrible resonances
that a lumped capacitor makes.

http://jahonen.kapsi.fi/Electronics/DIY%201k%20probe/

 

[John Larkin]

On 5 May 2019 08:54:39 -0700, Winfield Hill <hill@rowland.harvard.edu>
wrote:

John Larkin wrote...

I'm daydreaming a new product, and this is one problem:
https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0

The 2 pF makes really bad stuff happen ...

You have passive choices: Reduce the 2pF to 0.5pF
by making a 1:4 divider, you can make up for the
loss later if required. Add resistance in series.

200 or 300 ohms of resistive pickoff wouldn't hurt the loop much. Then
into a 50 ohm MMIC, like a MiniCircuits LEE-19 (we have those) to get
the signal level back.

I guess I could make the loop into an official 3-resistor tee
attenuator, but that could have more hazards than a simple pickoff
resistor.

I'll think about a capacitive divider too, but I also want to run low,
1 MHz maybe, so resistive is appealing.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Winfield Hill]

John Larkin wrote...

200 or 300 ohms of resistive pickoff wouldn't hurt the
loop much. Then into a 50 ohm MMIC, like a MiniCircuits
LEE-19 (we have those) to get the signal level back.

You may have an easier time achieving a wide bandwidth
for the pass-through, than the pickoff. SMT components
can be trouble makers. See how the LEE-19 incorporates
transmission-line signal paths within its structure.


--
Thanks,
- Win

 

[George Herold]

On Sunday, May 5, 2019 at 11:39:09 AM UTC-4, John Larkin wrote:

I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0

Huh it's 50 ohms all around? You could make it some sort of attenuator,
add some series C if 2 pF is too much.
George H.

The IC that I want to drive will be about a 2 pF load, and that wrecks
the 50 ohm microstrip transmission line that connects the two SMAs.
The idea is that a user can input a signal and either loop it into
another (several?) boxes, or screw on a terminator.

The 2 pF makes really bad stuff happen around 2 GHz or so, for the
loop-through path, and I'd like to go to 5. What I need is a
zero-capacitance buffer.

A phemt source follower might work, with a SAV551 or one of the
Skyworks parts. But fast source followers are also known as
oscillators.

Maybe I could use a series resistor into a 50 ohm MMIC amplifier. I'd
lose some signal but at least wouldn't have the horrible resonances
that a lumped capacitor makes.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Clifford Heath]

On 6/5/19 9:32 am, George Herold wrote:

On Sunday, May 5, 2019 at 11:39:09 AM UTC-4, John Larkin wrote:
I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0
Huh it's 50 ohms all around? You could make it some sort of attenuator,

That much is a given. You can't pick off some energy *and* leave it all
to pass through.

> add some series C if 2 pF is too much.

Which is what Win suggested as a 4:1 capacitive divider. Please do keep
up

JL should first accept that he's building a splitter, then decide how
ornate to make it. I'd be looking at resistive attenuators, boosted with
extra C to balance the buffer/amp input... depending on the importance
of flat input and output impedances, and source/load impedance isolation.

 

[Winfield Hill]

John Larkin wrote...

Winfield Hill wrote:
John Larkin wrote...

I'm daydreaming a new product, and this is one problem:
https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0

The 2 pF makes really bad stuff happen ...

You have passive choices: Reduce the 2pF to 0.5pF
by making a 1:4 divider, you can make up for the
loss later if required. Add resistance in series.

200 or 300 ohms of resistive pickoff wouldn't hurt
the loop much. Then into a 50 ohm MMIC, ...

An entirely passive system is not so unattractive.
No power supply requuired. Perfectly fine into a
scope, etc., or into an SMA amp module, provided
by the user.


--
Thanks,
- Win

 

[John Larkin]

On Sun, 5 May 2019 16:56:52 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:

On Sunday, May 5, 2019 at 11:39:09 AM UTC-4, John Larkin wrote:
I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0


The IC that I want to drive will be about a 2 pF load, and that wrecks
the 50 ohm microstrip transmission line that connects the two SMAs.
The idea is that a user can input a signal and either loop it into
another (several?) boxes, or screw on a terminator.

The 2 pF makes really bad stuff happen around 2 GHz or so, for the
loop-through path, and I'd like to go to 5. What I need is a
zero-capacitance buffer.

A phemt source follower might work, with a SAV551 or one of the
Skyworks parts. But fast source followers are also known as
oscillators.

Maybe I could use a series resistor into a 50 ohm MMIC amplifier. I'd
lose some signal but at least wouldn't have the horrible resonances
that a lumped capacitor makes.

Make one of these:
https://www.jfwindustries.com/product/50c-051-20-coupler/

Should just be something like so:
https://www.microwaves101.com/encyclopedias/resistive-taps

20 dB is a lot of signal to give up. 3 dB would be OK but wrecks the
thru path. A zero-pF follower would be ideal. Or else a resistive
pickoff and some wideband (as in 5 GHz) gain to get the signal level
back.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Sunday, May 5, 2019 at 11:39:09 AM UTC-4, John Larkin wrote:

I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0


The IC that I want to drive will be about a 2 pF load, and that wrecks
the 50 ohm microstrip transmission line that connects the two SMAs.
The idea is that a user can input a signal and either loop it into
another (several?) boxes, or screw on a terminator.

The 2 pF makes really bad stuff happen around 2 GHz or so, for the
loop-through path, and I'd like to go to 5. What I need is a
zero-capacitance buffer.

A phemt source follower might work, with a SAV551 or one of the
Skyworks parts. But fast source followers are also known as
oscillators.

Maybe I could use a series resistor into a 50 ohm MMIC amplifier. I'd
lose some signal but at least wouldn't have the horrible resonances
that a lumped capacitor makes.

Make one of these:
https://www.jfwindustries.com/product/50c-051-20-coupler/

Should just be something like so:
https://www.microwaves101.com/encyclopedias/resistive-taps

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Clifford Heath]

On 6/5/19 10:10 am, John Larkin wrote:

On Sun, 5 May 2019 16:56:52 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:

On Sunday, May 5, 2019 at 11:39:09 AM UTC-4, John Larkin wrote:
I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0


The IC that I want to drive will be about a 2 pF load, and that wrecks
the 50 ohm microstrip transmission line that connects the two SMAs.
The idea is that a user can input a signal and either loop it into
another (several?) boxes, or screw on a terminator.

The 2 pF makes really bad stuff happen around 2 GHz or so, for the
loop-through path, and I'd like to go to 5. What I need is a
zero-capacitance buffer.

A phemt source follower might work, with a SAV551 or one of the
Skyworks parts. But fast source followers are also known as
oscillators.

Maybe I could use a series resistor into a 50 ohm MMIC amplifier. I'd
lose some signal but at least wouldn't have the horrible resonances
that a lumped capacitor makes.

Make one of these:
https://www.jfwindustries.com/product/50c-051-20-coupler/

Should just be something like so:
https://www.microwaves101.com/encyclopedias/resistive-taps


20 dB is a lot of signal to give up. 3 dB would be OK but wrecks the
thru path. A zero-pF follower would be ideal. Or else a resistive
pickoff and some wideband (as in 5 GHz) gain to get the signal level
back.

Joe Dunsmore' coupler is 16dB (with 1.6dB through loss), but it's
trivial to modify the ratios. It's easy and cheap to build from
300KHz-3GHz, and with smaller parts, has been done to at least 13GHz.

The trade-off for broadband performance and directionality (port
isolation) is that it's resistive; up to half the input energy is simply
dissipated. If you don't need it to be directional, you can reduce the
losses, but if you don't want to either measure or pass reflected power,
you have to dissipate it.

Example through/coupled dB ratios:
6.0/6.0dB (equal arms)
4.7/7.8 (1/3, 2/3)
4.0/10 (1/5, 4/5)
3.23/16 (1/20, 19/20)

The 6dB version is limited at the botton end by the ferrite behaviour,
bit that can be improved using VK3DIP's technique with binocular cores,
as ripped off in:

<https://www.aliexpress.com/item/New-RF-SWR-Bridge-0-1-3000-MHZ-Return-Loss-Bridge-Reflection-Bridge-Antenna-Analyzer-VHF/32956081266.html>

Note that this is a faulty Chinese copy of a Ukrainian ripoff of
VK3DIP's design, but fix the errors and fit nicely-trimmed semi-rigid
hardline and the performance is remarkable from 100KHz to 3GHz. VNA test
results on request.

Better geometry and smaller resistors than 0805 would push that to 10GHz.

Clifford Heath.

 

On Monday, 6 May 2019 01:10:15 UTC+1, John Larkin wrote:

On Sun, 5 May 2019 16:56:52 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:
On Sunday, May 5, 2019 at 11:39:09 AM UTC-4, John Larkin wrote:

I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0


The IC that I want to drive will be about a 2 pF load, and that wrecks
the 50 ohm microstrip transmission line that connects the two SMAs.
The idea is that a user can input a signal and either loop it into
another (several?) boxes, or screw on a terminator.

The 2 pF makes really bad stuff happen around 2 GHz or so, for the
loop-through path, and I'd like to go to 5. What I need is a
zero-capacitance buffer.

A phemt source follower might work, with a SAV551 or one of the
Skyworks parts. But fast source followers are also known as
oscillators.

Maybe I could use a series resistor into a 50 ohm MMIC amplifier. I'd
lose some signal but at least wouldn't have the horrible resonances
that a lumped capacitor makes.

Make one of these:
https://www.jfwindustries.com/product/50c-051-20-coupler/

Should just be something like so:
https://www.microwaves101.com/encyclopedias/resistive-taps


20 dB is a lot of signal to give up. 3 dB would be OK but wrecks the
thru path. A zero-pF follower would be ideal. Or else a resistive
pickoff and some wideband (as in 5 GHz) gain to get the signal level
back.

What happens if you mount a very low C fet gate direct onto the co-ax between the connectors via an SM R? Then make the co-ax a planar pcb thing, as I expect it is.

 

[John Larkin]

On Sun, 05 May 2019 08:39:00 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0


The IC that I want to drive will be about a 2 pF load, and that wrecks
the 50 ohm microstrip transmission line that connects the two SMAs.
The idea is that a user can input a signal and either loop it into
another (several?) boxes, or screw on a terminator.

The 2 pF makes really bad stuff happen around 2 GHz or so, for the
loop-through path, and I'd like to go to 5. What I need is a
zero-capacitance buffer.

A phemt source follower might work, with a SAV551 or one of the
Skyworks parts. But fast source followers are also known as
oscillators.

Maybe I could use a series resistor into a 50 ohm MMIC amplifier. I'd
lose some signal but at least wouldn't have the horrible resonances
that a lumped capacitor makes.

A decent compromise is a pickoff that uses a 100 ohm to 50 ohm
divider, with a small inductor in series with the 50 to AC ground.
That gives me 1/3 of the customer voltage for my IC (a comparator) and
a bit of high frequency peaking where I probably want it. The damage
to the thru signal is small, even less at high frequencies.

It's an ADCMP572, and the 50 ohm resistor is actually inside the chip.

The phemt source follower is still interesting. I might try one for
fun.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Monday, 6 May 2019 05:38:15 UTC+1, John Larkin wrote:

You can compensate for some capacitive loading by narrowing the microstrip
track for a few mm on either side of the lumped capacitance.

John

 

[Clifford Heath]

On 6/5/19 7:22 pm, jrwalliker@gmail.com wrote:

On Monday, 6 May 2019 05:38:15 UTC+1, John Larkin wrote:

You can compensate for some capacitive loading by narrowing the microstrip
track for a few mm on either side of the lumped capacitance.

That still becomes as an LCL T-filter at about 2x what the roll-off
would have been. That's fine as long as you know it.

 

[John Larkin]

On Mon, 6 May 2019 02:22:54 -0700 (PDT), jrwalliker@gmail.com wrote:

On Monday, 6 May 2019 05:38:15 UTC+1, John Larkin wrote:

You can compensate for some capacitive loading by narrowing the microstrip
track for a few mm on either side of the lumped capacitance.

John

I Spiced that but it doesn't work for my geometry and speed. 2 pF of
pickoff capacitance is a huge hit on such a small short trace. The 50
ohm trace is about 3 pf/inch, and my whole run between connectors is
about 1".


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[John Larkin]

On Mon, 6 May 2019 08:50:23 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:

On Sunday, May 5, 2019 at 8:10:15 PM UTC-4, John Larkin wrote:
On Sun, 5 May 2019 16:56:52 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:

On Sunday, May 5, 2019 at 11:39:09 AM UTC-4, John Larkin wrote:
I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0


The IC that I want to drive will be about a 2 pF load, and that wrecks
the 50 ohm microstrip transmission line that connects the two SMAs.
The idea is that a user can input a signal and either loop it into
another (several?) boxes, or screw on a terminator.

The 2 pF makes really bad stuff happen around 2 GHz or so, for the
loop-through path, and I'd like to go to 5. What I need is a
zero-capacitance buffer.

A phemt source follower might work, with a SAV551 or one of the
Skyworks parts. But fast source followers are also known as
oscillators.

Maybe I could use a series resistor into a 50 ohm MMIC amplifier. I'd
lose some signal but at least wouldn't have the horrible resonances
that a lumped capacitor makes.

Make one of these:
https://www.jfwindustries.com/product/50c-051-20-coupler/

Should just be something like so:
https://www.microwaves101.com/encyclopedias/resistive-taps


20 dB is a lot of signal to give up. 3 dB would be OK but wrecks the
thru path. A zero-pF follower would be ideal. Or else a resistive
pickoff and some wideband (as in 5 GHz) gain to get the signal level
back.

Your signal level is nearly 4dBm, which in the RF world is HUUUUGE, so HUUUGE in fact many small signal monolithic amps introduce serious harmonic + spur content hitting their intercept point with that kind of *input* level. You knock that thing down to -16dBm where you can get reasonably harmonic and spur free amplification. But if you want to pay $100 for a high IIP3 amp to do a $0.99 job, have at it, your call. You want that 20dB coupling to isolate your through channel from the pickoff channel, the more attenuation the better. Attenuators are deliberately introduced in all kinds of circuits to kill non-linearities.

Did I mention 4 dBm?

We have the LEE-19 in stock, an 8 GHz 12 dB MMIC. Costs $1.19. A
resistor from the microstrip trace, hundreds of ohms, would get me
about net unity voltage gain at the MMIC output.

Too much gain doesn't worry me. I can sell the users attenuators.

The signal is a clock, into a comparator, so RF type distortion specs
don't matter.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[John Larkin]

On Sun, 5 May 2019 21:34:43 -0700 (PDT), tabbypurr@gmail.com wrote:

On Monday, 6 May 2019 01:10:15 UTC+1, John Larkin wrote:
On Sun, 5 May 2019 16:56:52 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:
On Sunday, May 5, 2019 at 11:39:09 AM UTC-4, John Larkin wrote:

I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0


The IC that I want to drive will be about a 2 pF load, and that wrecks
the 50 ohm microstrip transmission line that connects the two SMAs.
The idea is that a user can input a signal and either loop it into
another (several?) boxes, or screw on a terminator.

The 2 pF makes really bad stuff happen around 2 GHz or so, for the
loop-through path, and I'd like to go to 5. What I need is a
zero-capacitance buffer.

A phemt source follower might work, with a SAV551 or one of the
Skyworks parts. But fast source followers are also known as
oscillators.

Maybe I could use a series resistor into a 50 ohm MMIC amplifier. I'd
lose some signal but at least wouldn't have the horrible resonances
that a lumped capacitor makes.

Make one of these:
https://www.jfwindustries.com/product/50c-051-20-coupler/

Should just be something like so:
https://www.microwaves101.com/encyclopedias/resistive-taps


20 dB is a lot of signal to give up. 3 dB would be OK but wrecks the
thru path. A zero-pF follower would be ideal. Or else a resistive
pickoff and some wideband (as in 5 GHz) gain to get the signal level
back.

What happens if you mount a very low C fet gate direct onto the co-ax between the connectors via an SM R? Then make the co-ax a planar pcb thing, as I expect it is.

It will be a top layer trace, microstrip or CPW. I'd love to use a
source follower, probably a PHEMT or even a fast NPN... if it doesn't
oscillate. I could breadboard that maybe.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Sunday, May 5, 2019 at 8:10:15 PM UTC-4, John Larkin wrote:

On Sun, 5 May 2019 16:56:52 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:

On Sunday, May 5, 2019 at 11:39:09 AM UTC-4, John Larkin wrote:
I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0


The IC that I want to drive will be about a 2 pF load, and that wrecks
the 50 ohm microstrip transmission line that connects the two SMAs.
The idea is that a user can input a signal and either loop it into
another (several?) boxes, or screw on a terminator.

The 2 pF makes really bad stuff happen around 2 GHz or so, for the
loop-through path, and I'd like to go to 5. What I need is a
zero-capacitance buffer.

A phemt source follower might work, with a SAV551 or one of the
Skyworks parts. But fast source followers are also known as
oscillators.

Maybe I could use a series resistor into a 50 ohm MMIC amplifier. I'd
lose some signal but at least wouldn't have the horrible resonances
that a lumped capacitor makes.

Make one of these:
https://www.jfwindustries.com/product/50c-051-20-coupler/

Should just be something like so:
https://www.microwaves101.com/encyclopedias/resistive-taps


20 dB is a lot of signal to give up. 3 dB would be OK but wrecks the
thru path. A zero-pF follower would be ideal. Or else a resistive
pickoff and some wideband (as in 5 GHz) gain to get the signal level
back.

Your signal level is nearly 4dBm, which in the RF world is HUUUUGE, so HUUUGE in fact many small signal monolithic amps introduce serious harmonic + spur content hitting their intercept point with that kind of *input* level. You knock that thing down to -16dBm where you can get reasonably harmonic and spur free amplification. But if you want to pay $100 for a high IIP3 amp to do a $0.99 job, have at it, your call. You want that 20dB coupling to isolate your through channel from the pickoff channel, the more attenuation the better. Attenuators are deliberately introduced in all kinds of circuits to kill non-linearities.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Phil Hobbs]

On 5/6/19 12:38 AM, John Larkin wrote:

On Sun, 05 May 2019 08:39:00 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:



I'm daydreaming a new product, and this is one problem:

https://www.dropbox.com/s/oo9gixme2mocsc3/kbox_pickoff.JPG?dl=0


The IC that I want to drive will be about a 2 pF load, and that wrecks
the 50 ohm microstrip transmission line that connects the two SMAs.
The idea is that a user can input a signal and either loop it into
another (several?) boxes, or screw on a terminator.

The 2 pF makes really bad stuff happen around 2 GHz or so, for the
loop-through path, and I'd like to go to 5. What I need is a
zero-capacitance buffer.

A phemt source follower might work, with a SAV551 or one of the
Skyworks parts. But fast source followers are also known as
oscillators.

Maybe I could use a series resistor into a 50 ohm MMIC amplifier. I'd
lose some signal but at least wouldn't have the horrible resonances
that a lumped capacitor makes.

A decent compromise is a pickoff that uses a 100 ohm to 50 ohm
divider, with a small inductor in series with the 50 to AC ground.
That gives me 1/3 of the customer voltage for my IC (a comparator) and
a bit of high frequency peaking where I probably want it. The damage
to the thru signal is small, even less at high frequencies.

It's an ADCMP572, and the 50 ohm resistor is actually inside the chip.

The phemt source follower is still interesting. I might try one for
fun.

The SKY65050 makes a semi-decent follower, about like your average JFET.
The Avago ones (ATF38143 etc.) have such low drain impedances that
their gains as a follower are down around 0.6 or something horrible like
that. Small pHEMTs are surprisingly stable due to their very low
interelectrode capacitances--you have to really work to make one oscillate.

I haven't tried the Mini Circuits ones yet, though I have a hundred or
so in stock. The new Renesas 12-GHz class pHEMTs look pretty
interesting too.

Bootstrapping a pHEMT with a SiGe:C transistor (BFP640) makes a nearly
perfect gain stage, except that you have to de-Q the base of the BJT or
it'll oscillate at 14 GHz or so. I usually use a BLM18BB05 (5 ohms at
100 MHz) for that. Dunno how it would work at 5 GHz--my application was
at a bandwidth of 100 MHz.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com