MPPC front end with SAV-551+ pHEMT bootstrap

[Phil Hobbs]

So I'm doing this multi-pixel photon counter front end for a SEM
cathodoluminescence detector. The proto uses a Hamamatsu
S13362-3050DG cooled MPPC running at a gain of about 1.7E6, so each
detection event produces

1.7E6 e = 0.3 pC,

with asymmetrical rise/fall times of about 5/30 ns. To overcome the 320
pF capacitance and maintain a 40-MHz bandwidth with reasonable noise
performance, I built a bootstrap from one of the newish Mini-Circuits
SAV-551+ pHEMTs on fine pitch blob board. It promptly oscillated at 5
GHz, but my trusty TDS 694C can see that.

I often scout that sort of problem using a 4-GHz FET probe with a 1 kV
disc ceramic cap stuck in where the probe tip should go, and no ground
connection--you just lay it someplace nearby and it picks up whatever's
going. (The 1 kV caps have leads of the right diameter for the probe.)

Once I got the oscillation stopped, the noise floor in a 60-MHz
bandwidth was 900 uV RMS after applying a gain of 8.2. The TIA is an
ADA4899-1 with a 1k feedback resistor, so the input-referred current
noise is

i_N = 900uV/8.2/1000/sqrt(60 MHz) = 14 pA/sqrt(Hz).

The Johnson noise of the 1k feedback resistor is 4.0 pA/sqrt(Hz).

Without the bootstrap, the noise would be dominated by the e_N C
contribution due to the MPPC capacitance differentiating the voltage
noise of the op amp:

i_NC = e_Namp * (2*pi*f*320 pF),

and the RMS definite integral from 0 to f_0 is

I_NC = 2*pi * 320 pF * e_Namp * sqrt(integral (f**2))
0, f_0

The integral term is sqrt(f_0**3/3), so the total e_N*C noise is

I_NC = 2*pi * 320 pF * 1 nV/sqrt(Hz)/sqrt(3) * f_0**1.5


The ADA4899's 1-Hz input noise is about a nanovolt, so without the
bootstrap it would be approximately

i_NC ~ 6.3 * 1E-9 * 320E-12 * 60e6**1.5/sqrt(3) = 540 pA/sqrt(Hz).

In order to get this down to the 14 pA level, the voltage noise of the
pHEMT would have to be down around 26 pV/sqrt(Hz), which is at least a
factor of five too low, even with the most optimistic assumptions.
Double-checking underway.

In any event, single-photon events are easily visible, and the dynamic
range is pretty good, limited by the number of MPPC pixels (3600) and
their recovery time of ~20 ns--assuming uniform illumination,
sensitivity will drop by half at

N ~ #pixels/t_rec

or

2.8 nA primary photocurrent. That works out to almost 50 mA after
multiplication, which would turn the chip to lava, so we aren't going to
be limited that way.

Fun stuff.

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

 

[John Larkin]

On Fri, 9 Aug 2019 11:08:41 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

So I'm doing this multi-pixel photon counter front end for a SEM
cathodoluminescence detector. The proto uses a Hamamatsu



S13362-3050DG cooled MPPC running at a gain of about 1.7E6, so each

detection event produces

1.7E6 e = 0.3 pC,

with asymmetrical rise/fall times of about 5/30 ns. To overcome the 320
pF capacitance and maintain a 40-MHz bandwidth with reasonable noise
performance, I built a bootstrap from one of the newish Mini-Circuits
SAV-551+ pHEMTs on fine pitch blob board. It promptly oscillated at 5
GHz, but my trusty TDS 694C can see that.

I recently built a 600 MHz CCRO Colpitts oscillator with a SAV551, and
it oscillated at some astronomical frequency above 600. Prudently, I
allowed for a gate resistor, and it needed it. The resistor does
probably contribute to phase noise. Maybe I should stick to bipolars.

Did you lay out a board or kluge up something? I did both fet and
bipolar versions of my oscillator, and a bunch of other stuff, on one
board from PCBWAY.

PCBWAY is great but their solder masks are sloppy, not good for BGAs.

https://www.dropbox.com/s/hppjadia3a505hi/Zoom_3.jpg?raw=1


I do have a little DC data on the SAV551 thing. It's impressive.

Rds-on * Cd-off = 0.8 ps. Almost as good as a relay!



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Phil Hobbs]

On 8/9/19 11:52 AM, John Larkin wrote:

On Fri, 9 Aug 2019 11:08:41 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

So I'm doing this multi-pixel photon counter front end for a SEM
cathodoluminescence detector. The proto uses a Hamamatsu


S13362-3050DG cooled MPPC running at a gain of about 1.7E6, so each
detection event produces

1.7E6 e = 0.3 pC,

with asymmetrical rise/fall times of about 5/30 ns. To overcome the 320
pF capacitance and maintain a 40-MHz bandwidth with reasonable noise
performance, I built a bootstrap from one of the newish Mini-Circuits
SAV-551+ pHEMTs on fine pitch blob board. It promptly oscillated at 5
GHz, but my trusty TDS 694C can see that.

I recently built a 600 MHz CCRO Colpitts oscillator with a SAV551, and
it oscillated at some astronomical frequency above 600. Prudently, I
allowed for a gate resistor, and it needed it. The resistor does
probably contribute to phase noise. Maybe I should stick to bipolars.

I usually use a Murata BLM18BB010 or 005 bead (10 or 5 ohms @ 100 MHz
respectively). They peak at some much higher value out at 3-4 GHz where
the problems usually lurk.

Did you lay out a board or kluge up something? I did both fet and
bipolar versions of my oscillator, and a bunch of other stuff, on one
board from PCBWAY.

I built it on a tiny piece of blob board, BoardWorX SMT-400. Photo at
<https://electrooptical.net/www/sed/MPPCfrontEndPHEMT.jpg>.

The bootstrap is at bottom right, the ADA4899 is at bottom left (just to
the right of the TO-92 voltage regulator) and the DIP at the top is an
LT1260 triple CFA that I had in the drawer.

PCBWAY is great but their solder masks are sloppy, not good for BGAs.

Never tried one, so I don't know. We use them for everything, though we
may go back to Pentalogix for assembly due to the duty--it's a drag
having to pay duty on the whole finished assembly.

https://www.dropbox.com/s/hppjadia3a505hi/Zoom_3.jpg?raw=1

Yeah, not great. I haven't seen one that bad so far.

I do have a little DC data on the SAV551 thing. It's impressive.

Rds-on * Cd-off = 0.8 ps. Almost as good as a relay!

The noise plots hint at a very low 1/f corner, too. On P. 7 of the
datasheet there's a plot of Fmin (minimum noise figure) vs. frequency
that shows a value below 0.1 dB at 500 MHz, and a table on P. 8 showing
that it's 0.084 dB with an optimal gamma of 0.38 at 24 degrees phase.
0.084 dB is a fractional added power of

10**0.0084 - 1 ~ 0.0084 * ln(10) = 1.9%.

Ignoring the phase and loading, that means that our optimal noise match is

Ropt = 50*(1+0.38)/(1-0.38) = 111 ohms

and the noise voltage is about

sqrt(0.019*111/60.4) = 190 pV/sqrt(Hz).

That's quite dramatically better than the Avago parts, which were about
300 pV. So maybe that 55 pV number is vaguely conceivable.


--
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

 

[Phil Hobbs]

On 8/9/19 11:08 AM, Phil Hobbs wrote:

So I'm doing this multi-pixel photon counter front end for a SEM
cathodoluminescence detector. The proto uses a Hamamatsu
S13362-3050DG cooled MPPC running at a gain of about 1.7E6, so
each detection event produces

1.7E6 e = 0.3 pC,

with asymmetrical rise/fall times of about 5/30 ns. To overcome the
320 pF capacitance and maintain a 40-MHz bandwidth with reasonable
noise performance, I built a bootstrap from one of the newish
Mini-Circuits SAV-551+ pHEMTs on fine pitch blob board. It promptly
oscillated at 5 GHz, but my trusty TDS 694C can see that.

I often scout that sort of problem using a 4-GHz FET probe with a 1
kV disc ceramic cap stuck in where the probe tip should go, and no
ground connection--you just lay it someplace nearby and it picks up
whatever's going. (The 1 kV caps have leads of the right diameter
for the probe.)

fixing fixing
Once I got the oscillation stopped, the noise floor in a 50-MHz
bandwidth was 550 uV RMS after applying a gain of 8.2. The TIA is an
ADA4899-1 with a 1k feedback resistor, so the input-referred current
noise is

I_N = 550uV/8.2/1000 = 67 nA, or 9.5 pA/sqrt(Hz) average.

The Johnson noise of the 1k feedback resistor is 4.0 pA/sqrt(Hz).

Without the bootstrap, the noise would be dominated by the e_N C
contribution due to the MPPC capacitance differentiating the voltage
noise of the op amp:

i_NC = e_Namp * (2*pi*f*320 pF),

and the RMS definite integral from 0 to f_0 is

I_NC = 2*pi * 320 pF * e_Namp * sqrt(integral (f**2)) 0, f_0

The integral term is sqrt(f_0**3/3), so the total e_N*C noise is

I_NC = 2*pi * 320 pF * 1 nV/sqrt(Hz)/sqrt(3) * f_0**1.5

fixing fixing fixing

The ADA4899's 1-Hz input noise is about a nanovolt, so without the
bootstrap it would be approximately

i_NC ~ 6.3 * 1E-9 * 320E-12 * 60e6**1.5/sqrt(3) = 540 nA.

In order to get this down to the 67-nA level, the voltage noise of
the pHEMT would have to be down around 67/540 = 124 pV/sqrt(Hz).

As I estimated 190 pV/sqrt(Hz) at 500 MHz in my other post, this is
actually a plausible number near baseband--and one that's
_SEVEN_POINT_SIX_DECIBELS_ quieter than the ATF38143! Now I really have
to make an amp and measure it.

In any event, single-photon events are easily visible, and the
dynamic range is pretty good, limited by the number of MPPC pixels
(3600) and their recovery time of ~20 ns--assuming uniform
illumination, sensitivity will drop by half at

N ~ #pixels/t_rec

or

2.8 nA primary photocurrent. That works out to almost 50 mA after
multiplication, which would turn the chip to lava, so we aren't going
to be limited that way.

Fun stuff.

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

 

[John Larkin]

On Fri, 9 Aug 2019 12:35:01 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 8/9/19 11:52 AM, John Larkin wrote:
On Fri, 9 Aug 2019 11:08:41 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

So I'm doing this multi-pixel photon counter front end for a SEM
cathodoluminescence detector. The proto uses a Hamamatsu


S13362-3050DG cooled MPPC running at a gain of about 1.7E6, so each
detection event produces

1.7E6 e = 0.3 pC,

with asymmetrical rise/fall times of about 5/30 ns. To overcome the 320
pF capacitance and maintain a 40-MHz bandwidth with reasonable noise
performance, I built a bootstrap from one of the newish Mini-Circuits
SAV-551+ pHEMTs on fine pitch blob board. It promptly oscillated at 5
GHz, but my trusty TDS 694C can see that.

I recently built a 600 MHz CCRO Colpitts oscillator with a SAV551, and
it oscillated at some astronomical frequency above 600. Prudently, I
allowed for a gate resistor, and it needed it. The resistor does
probably contribute to phase noise. Maybe I should stick to bipolars.

I usually use a Murata BLM18BB010 or 005 bead (10 or 5 ohms @ 100 MHz
respectively). They peak at some much higher value out at 3-4 GHz where
the problems usually lurk.


Did you lay out a board or kluge up something? I did both fet and
bipolar versions of my oscillator, and a bunch of other stuff, on one
board from PCBWAY.

I built it on a tiny piece of blob board, BoardWorX SMT-400. Photo at
https://electrooptical.net/www/sed/MPPCfrontEndPHEMT.jpg>.

Aggg! That looks like a junkyard after a nuclear war!

The bootstrap is at bottom right, the ADA4899 is at bottom left (just to
the right of the TO-92 voltage regulator) and the DIP at the top is an
LT1260 triple CFA that I had in the drawer.


PCBWAY is great but their solder masks are sloppy, not good for BGAs.

Never tried one, so I don't know. We use them for everything, though we
may go back to Pentalogix for assembly due to the duty--it's a drag
having to pay duty on the whole finished assembly.

https://www.dropbox.com/s/hppjadia3a505hi/Zoom_3.jpg?raw=1

Yeah, not great. I haven't seen one that bad so far.


I do have a little DC data on the SAV551 thing. It's impressive.

Rds-on * Cd-off = 0.8 ps. Almost as good as a relay!

The noise plots hint at a very low 1/f corner, too. On P. 7 of the
datasheet there's a plot of Fmin (minimum noise figure) vs. frequency
that shows a value below 0.1 dB at 500 MHz, and a table on P. 8 showing
that it's 0.084 dB with an optimal gamma of 0.38 at 24 degrees phase.
0.084 dB is a fractional added power of

Somehow a noise figure below 1 dB sounds impossible to me. 0.1 dB is
an equivalent temperature of 7K.

 

[John Larkin]

On Fri, 9 Aug 2019 15:04:04 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 8/9/19 1:51 PM, John Larkin wrote:
On Fri, 9 Aug 2019 12:35:01 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 8/9/19 11:52 AM, John Larkin wrote:
On Fri, 9 Aug 2019 11:08:41 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

So I'm doing this multi-pixel photon counter front end for a SEM
cathodoluminescence detector. The proto uses a Hamamatsu


S13362-3050DG cooled MPPC running at a gain of about 1.7E6, so each
detection event produces

1.7E6 e = 0.3 pC,

with asymmetrical rise/fall times of about 5/30 ns. To overcome the 320
pF capacitance and maintain a 40-MHz bandwidth with reasonable noise
performance, I built a bootstrap from one of the newish Mini-Circuits
SAV-551+ pHEMTs on fine pitch blob board. It promptly oscillated at 5
GHz, but my trusty TDS 694C can see that.

I recently built a 600 MHz CCRO Colpitts oscillator with a SAV551, and
it oscillated at some astronomical frequency above 600. Prudently, I
allowed for a gate resistor, and it needed it. The resistor does
probably contribute to phase noise. Maybe I should stick to bipolars.

I usually use a Murata BLM18BB010 or 005 bead (10 or 5 ohms @ 100 MHz
respectively). They peak at some much higher value out at 3-4 GHz where
the problems usually lurk.


Did you lay out a board or kluge up something? I did both fet and
bipolar versions of my oscillator, and a bunch of other stuff, on one
board from PCBWAY.

I built it on a tiny piece of blob board, BoardWorX SMT-400. Photo at
https://electrooptical.net/www/sed/MPPCfrontEndPHEMT.jpg>.

Aggg! That looks like a junkyard after a nuclear war!

It was prettier before I started debugging the 5-GHz oscillation. But
it's in a nice die cast box with a clear coat.




The bootstrap is at bottom right, the ADA4899 is at bottom left (just to
the right of the TO-92 voltage regulator) and the DIP at the top is an
LT1260 triple CFA that I had in the drawer.


PCBWAY is great but their solder masks are sloppy, not good for BGAs.

Never tried one, so I don't know. We use them for everything, though we
may go back to Pentalogix for assembly due to the duty--it's a drag
having to pay duty on the whole finished assembly.

https://www.dropbox.com/s/hppjadia3a505hi/Zoom_3.jpg?raw=1

Yeah, not great. I haven't seen one that bad so far.


I do have a little DC data on the SAV551 thing. It's impressive.

Rds-on * Cd-off = 0.8 ps. Almost as good as a relay!

The noise plots hint at a very low 1/f corner, too. On P. 7 of the
datasheet there's a plot of Fmin (minimum noise figure) vs. frequency
that shows a value below 0.1 dB at 500 MHz, and a table on P. 8 showing
that it's 0.084 dB with an optimal gamma of 0.38 at 24 degrees phase.
0.084 dB is a fractional added power of

Somehow a noise figure below 1 dB sounds impossible to me. 0.1 dB is
an equivalent temperature of 7K.


2-D electron gas devices (which is what a pHEMT is) can have very very
low scattering. I'll spend part of tomorrow building an amp and
measuring its actual noise.

The Early voltage is pretty good too--about 16 volts, and weirdly better
at lower V_DS. So you can get some actual voltage gain out of them.

Sounds like a weird slope somewhere?

Different thing entirely, but the actual it-dies drain voltage is
about 11. They are probably OK to run at 5 or 6.

 

[Phil Hobbs]

On 8/9/19 2:51 PM, George Herold wrote:

On Friday, August 9, 2019 at 12:35:09 PM UTC-4, Phil Hobbs wrote:
On 8/9/19 11:52 AM, John Larkin wrote:
On Fri, 9 Aug 2019 11:08:41 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

So I'm doing this multi-pixel photon counter front end for a SEM
cathodoluminescence detector. The proto uses a Hamamatsu


S13362-3050DG cooled MPPC running at a gain of about 1.7E6, so each
detection event produces

1.7E6 e = 0.3 pC,

with asymmetrical rise/fall times of about 5/30 ns. To overcome the 320
pF capacitance and maintain a 40-MHz bandwidth with reasonable noise
performance, I built a bootstrap from one of the newish Mini-Circuits
SAV-551+ pHEMTs on fine pitch blob board. It promptly oscillated at 5
GHz, but my trusty TDS 694C can see that.

I recently built a 600 MHz CCRO Colpitts oscillator with a SAV551, and
it oscillated at some astronomical frequency above 600. Prudently, I
allowed for a gate resistor, and it needed it. The resistor does
probably contribute to phase noise. Maybe I should stick to bipolars.

I usually use a Murata BLM18BB010 or 005 bead (10 or 5 ohms @ 100 MHz
respectively). They peak at some much higher value out at 3-4 GHz where
the problems usually lurk.


Did you lay out a board or kluge up something? I did both fet and
bipolar versions of my oscillator, and a bunch of other stuff, on one
board from PCBWAY.

I built it on a tiny piece of blob board, BoardWorX SMT-400. Photo at
https://electrooptical.net/www/sed/MPPCfrontEndPHEMT.jpg>.

The bootstrap is at bottom right, the ADA4899 is at bottom left (just to
the right of the TO-92 voltage regulator) and the DIP at the top is an
LT1260 triple CFA that I had in the drawer.

The ADA4899 is the solder blob, with two blue (wire wrap) wires and a tiny
piece of coax coming from it?

Yup. That's for the power pad. The feedback network (1 k || 3 pF) is
sitting right on pins 1 and 2.

BTW the wire cutters arrived, very nice. Thanks!

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

 

[Phil Hobbs]

On 8/9/19 1:51 PM, John Larkin wrote:

On Fri, 9 Aug 2019 12:35:01 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 8/9/19 11:52 AM, John Larkin wrote:
On Fri, 9 Aug 2019 11:08:41 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

So I'm doing this multi-pixel photon counter front end for a SEM
cathodoluminescence detector. The proto uses a Hamamatsu


S13362-3050DG cooled MPPC running at a gain of about 1.7E6, so each
detection event produces

1.7E6 e = 0.3 pC,

with asymmetrical rise/fall times of about 5/30 ns. To overcome the 320
pF capacitance and maintain a 40-MHz bandwidth with reasonable noise
performance, I built a bootstrap from one of the newish Mini-Circuits
SAV-551+ pHEMTs on fine pitch blob board. It promptly oscillated at 5
GHz, but my trusty TDS 694C can see that.

I recently built a 600 MHz CCRO Colpitts oscillator with a SAV551, and
it oscillated at some astronomical frequency above 600. Prudently, I
allowed for a gate resistor, and it needed it. The resistor does
probably contribute to phase noise. Maybe I should stick to bipolars.

I usually use a Murata BLM18BB010 or 005 bead (10 or 5 ohms @ 100 MHz
respectively). They peak at some much higher value out at 3-4 GHz where
the problems usually lurk.


Did you lay out a board or kluge up something? I did both fet and
bipolar versions of my oscillator, and a bunch of other stuff, on one
board from PCBWAY.

I built it on a tiny piece of blob board, BoardWorX SMT-400. Photo at
https://electrooptical.net/www/sed/MPPCfrontEndPHEMT.jpg>.

Aggg! That looks like a junkyard after a nuclear war!

It was prettier before I started debugging the 5-GHz oscillation. But
it's in a nice die cast box with a clear coat.

The bootstrap is at bottom right, the ADA4899 is at bottom left (just to
the right of the TO-92 voltage regulator) and the DIP at the top is an
LT1260 triple CFA that I had in the drawer.


PCBWAY is great but their solder masks are sloppy, not good for BGAs.

Never tried one, so I don't know. We use them for everything, though we
may go back to Pentalogix for assembly due to the duty--it's a drag
having to pay duty on the whole finished assembly.

https://www.dropbox.com/s/hppjadia3a505hi/Zoom_3.jpg?raw=1

Yeah, not great. I haven't seen one that bad so far.


I do have a little DC data on the SAV551 thing. It's impressive.

Rds-on * Cd-off = 0.8 ps. Almost as good as a relay!

The noise plots hint at a very low 1/f corner, too. On P. 7 of the
datasheet there's a plot of Fmin (minimum noise figure) vs. frequency
that shows a value below 0.1 dB at 500 MHz, and a table on P. 8 showing
that it's 0.084 dB with an optimal gamma of 0.38 at 24 degrees phase.
0.084 dB is a fractional added power of

Somehow a noise figure below 1 dB sounds impossible to me. 0.1 dB is
an equivalent temperature of 7K.

2-D electron gas devices (which is what a pHEMT is) can have very very
low scattering. I'll spend part of tomorrow building an amp and
measuring its actual noise.

The Early voltage is pretty good too--about 16 volts, and weirdly better
at lower V_DS. So you can get some actual voltage gain out of them.

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

 

[George Herold]

On Friday, August 9, 2019 at 12:35:09 PM UTC-4, Phil Hobbs wrote:

On 8/9/19 11:52 AM, John Larkin wrote:
On Fri, 9 Aug 2019 11:08:41 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

So I'm doing this multi-pixel photon counter front end for a SEM
cathodoluminescence detector. The proto uses a Hamamatsu


S13362-3050DG cooled MPPC running at a gain of about 1.7E6, so each
detection event produces

1.7E6 e = 0.3 pC,

with asymmetrical rise/fall times of about 5/30 ns. To overcome the 320
pF capacitance and maintain a 40-MHz bandwidth with reasonable noise
performance, I built a bootstrap from one of the newish Mini-Circuits
SAV-551+ pHEMTs on fine pitch blob board. It promptly oscillated at 5
GHz, but my trusty TDS 694C can see that.

I recently built a 600 MHz CCRO Colpitts oscillator with a SAV551, and
it oscillated at some astronomical frequency above 600. Prudently, I
allowed for a gate resistor, and it needed it. The resistor does
probably contribute to phase noise. Maybe I should stick to bipolars.

I usually use a Murata BLM18BB010 or 005 bead (10 or 5 ohms @ 100 MHz
respectively). They peak at some much higher value out at 3-4 GHz where
the problems usually lurk.


Did you lay out a board or kluge up something? I did both fet and
bipolar versions of my oscillator, and a bunch of other stuff, on one
board from PCBWAY.

I built it on a tiny piece of blob board, BoardWorX SMT-400. Photo at
https://electrooptical.net/www/sed/MPPCfrontEndPHEMT.jpg>.

The bootstrap is at bottom right, the ADA4899 is at bottom left (just to
the right of the TO-92 voltage regulator) and the DIP at the top is an
LT1260 triple CFA that I had in the drawer.

The ADA4899 is the solder blob, with two blue (wire wrap) wires and a tiny
piece of coax coming from it?

George H.

PCBWAY is great but their solder masks are sloppy, not good for BGAs.

Never tried one, so I don't know. We use them for everything, though we
may go back to Pentalogix for assembly due to the duty--it's a drag
having to pay duty on the whole finished assembly.

https://www.dropbox.com/s/hppjadia3a505hi/Zoom_3.jpg?raw=1

Yeah, not great. I haven't seen one that bad so far.


I do have a little DC data on the SAV551 thing. It's impressive.

Rds-on * Cd-off = 0.8 ps. Almost as good as a relay!

The noise plots hint at a very low 1/f corner, too. On P. 7 of the
datasheet there's a plot of Fmin (minimum noise figure) vs. frequency
that shows a value below 0.1 dB at 500 MHz, and a table on P. 8 showing
that it's 0.084 dB with an optimal gamma of 0.38 at 24 degrees phase.
0.084 dB is a fractional added power of

10**0.0084 - 1 ~ 0.0084 * ln(10) = 1.9%.

Ignoring the phase and loading, that means that our optimal noise match is

Ropt = 50*(1+0.38)/(1-0.38) = 111 ohms

and the noise voltage is about

sqrt(0.019*111/60.4) = 190 pV/sqrt(Hz).

That's quite dramatically better than the Avago parts, which were about
300 pV. So maybe that 55 pV number is vaguely conceivable.


--
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

 

[Phil Hobbs]

On 8/9/19 3:29 PM, John Larkin wrote:

On Fri, 9 Aug 2019 15:04:04 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 8/9/19 1:51 PM, John Larkin wrote:
On Fri, 9 Aug 2019 12:35:01 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 8/9/19 11:52 AM, John Larkin wrote:
On Fri, 9 Aug 2019 11:08:41 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

So I'm doing this multi-pixel photon counter front end for a SEM
cathodoluminescence detector. The proto uses a Hamamatsu


S13362-3050DG cooled MPPC running at a gain of about 1.7E6, so each
detection event produces

1.7E6 e = 0.3 pC,

with asymmetrical rise/fall times of about 5/30 ns. To overcome the 320
pF capacitance and maintain a 40-MHz bandwidth with reasonable noise
performance, I built a bootstrap from one of the newish Mini-Circuits
SAV-551+ pHEMTs on fine pitch blob board. It promptly oscillated at 5
GHz, but my trusty TDS 694C can see that.

I recently built a 600 MHz CCRO Colpitts oscillator with a SAV551, and
it oscillated at some astronomical frequency above 600. Prudently, I
allowed for a gate resistor, and it needed it. The resistor does
probably contribute to phase noise. Maybe I should stick to bipolars.

I usually use a Murata BLM18BB010 or 005 bead (10 or 5 ohms @ 100 MHz
respectively). They peak at some much higher value out at 3-4 GHz where
the problems usually lurk.


Did you lay out a board or kluge up something? I did both fet and
bipolar versions of my oscillator, and a bunch of other stuff, on one
board from PCBWAY.

I built it on a tiny piece of blob board, BoardWorX SMT-400. Photo at
https://electrooptical.net/www/sed/MPPCfrontEndPHEMT.jpg>.

Aggg! That looks like a junkyard after a nuclear war!

It was prettier before I started debugging the 5-GHz oscillation. But
it's in a nice die cast box with a clear coat.




The bootstrap is at bottom right, the ADA4899 is at bottom left (just to
the right of the TO-92 voltage regulator) and the DIP at the top is an
LT1260 triple CFA that I had in the drawer.


PCBWAY is great but their solder masks are sloppy, not good for BGAs.

Never tried one, so I don't know. We use them for everything, though we
may go back to Pentalogix for assembly due to the duty--it's a drag
having to pay duty on the whole finished assembly.

https://www.dropbox.com/s/hppjadia3a505hi/Zoom_3.jpg?raw=1

Yeah, not great. I haven't seen one that bad so far.


I do have a little DC data on the SAV551 thing. It's impressive.

Rds-on * Cd-off = 0.8 ps. Almost as good as a relay!

The noise plots hint at a very low 1/f corner, too. On P. 7 of the
datasheet there's a plot of Fmin (minimum noise figure) vs. frequency
that shows a value below 0.1 dB at 500 MHz, and a table on P. 8 showing
that it's 0.084 dB with an optimal gamma of 0.38 at 24 degrees phase.
0.084 dB is a fractional added power of

Somehow a noise figure below 1 dB sounds impossible to me. 0.1 dB is
an equivalent temperature of 7K.


2-D electron gas devices (which is what a pHEMT is) can have very very
low scattering. I'll spend part of tomorrow building an amp and
measuring its actual noise.

The Early voltage is pretty good too--about 16 volts, and weirdly better
at lower V_DS. So you can get some actual voltage gain out of them.


Sounds like a weird slope somewhere?

It looks like some other leakage mechanism turning on at around 2 V D-S.
Maybe a region with different doping or something like that.

Different thing entirely, but the actual it-dies drain voltage is
about 11. They are probably OK to run at 5 or 6.

Good to know, thanks.

If this thing is really that good, I'm going to have a lot of fun with
it. Hopefully its 1/f corner isn't as horrible as the SKY65050's (30
MHz!). I doubt it'll get the Gerhard Seal of Approval at low baseband,
of course, but maybe he can wire up 10,000 chopamps in parallel.

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

 

[John Larkin]

On Fri, 9 Aug 2019 15:04:04 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

The Early voltage is pretty good too--about 16 volts, and weirdly better
at lower V_DS. So you can get some actual voltage gain out of them.

Lots of gain. They go from about off to on pretty hard in a few tenths
of a volt.

This is from my phemt NOR gate idea:

https://www.dropbox.com/s/xrq0fdbezs8651m/DSC03248.JPG?dl=0

Voltage gain must be around 50 in the best part.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Jan Panteltje]

On a sunny day (Fri, 09 Aug 2019 12:29:35 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<54irkehtnmvh5ps1q17am35v83ouv2kt0o@4ax.com>:

On Fri, 9 Aug 2019 12:35:01 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:
The noise plots hint at a very low 1/f corner, too. On P. 7 of the
datasheet there's a plot of Fmin (minimum noise figure) vs. frequency
that shows a value below 0.1 dB at 500 MHz, and a table on P. 8 showing
that it's 0.084 dB with an optimal gamma of 0.38 at 24 degrees phase.
0.084 dB is a fractional added power of

Somehow a noise figure below 1 dB sounds impossible to me. 0.1 dB is
an equivalent temperature of 7K.


2-D electron gas devices (which is what a pHEMT is) can have very very
low scattering. I'll spend part of tomorrow building an amp and
measuring its actual noise.

The Early voltage is pretty good too--about 16 volts, and weirdly better
at lower V_DS. So you can get some actual voltage gain out of them.


Sounds like a weird slope somewhere?

Different thing entirely, but the actual it-dies drain voltage is
about 11. They are probably OK to run at 5 or 6.

The preamp in my Octagon LNB is the NE3512S02 N-CHANNEL HJ-FET.
Seems EOL, but mysteriously is in my now 1 year old LNB.
That FET has a noise of 0.35 dB at 2 GHz, and 0.4 dB at 10 GHz (where the LNB works).
It is supposed to be one of the best LNBs around.
ebay still has those from many sellers:
https://www.ebay.com/itm/170842506722
Maybe China is making clone FETs?