> On Thu, 27 Feb 2014 17:56:05 -0800, Joerg <invalid@invalid.invalid>
> wrote:
>
>> John Larkin wrote:
>>> On Thu, 27 Feb 2014 17:59:16 +0100, Gerhard Hoffmann <dk4xp@arcor.de> wrote:
>>>
>>>> Am 27.02.2014 16:02, schrieb John Larkin:
>>>>> Several people still make SRDs. M-pulse, Metelics, MAcom (all SRD makers start
>>>>> with "M")
>>>>>
>>>>> MA44767 and MA44769 are SOT23 distributor items, 50-75 cents range.
>>>>>
>>>> Ah, found them under varactors @Mouser, at least the MA144769-287T
>>>> But 600 ps transition time is not that wonderful anymore, got
>>>> half a ns from Fairchild NC7sz04p5x :-)
>>>> Nobody escapes the CMOS steamroller!
>>>>
>>>> thanks, Gerhard
>>> The 44769 is rated 150 ps transition time, but they will go a bit faster if you
>>> drive them hard.
>>>
>>> The fastest catalog items are around 25-30 ps.
>>>
>>> http://www.aeroflex.com/AMS/Metelics/micro-metelics-prods-SRDs-beamlead.cfm
>>>
>>> Somebody makes some really fast 0402 sized parts, can't remember who.
>>>
>>> Fast SRDs don't store much charge, so they are hard to drive.
>>>
>> <100psec should be doable with a BFP740 and similar ones with the base
>> driven sledgehammer-style. Of course, only very few volts allowed at the
>> collector.
>
> Have you tried that? My experiments along those lines have been
> disappointing.
>
Not with the BFP yet but with a BFR92 and it performed quite nicely.
What happened in your case? How did you drive them?
> PHEMTS switch screamingly fast, and the gates are relatively easy to
> drive. Good SRD drivers. In the old tek samplers, they usually used an
> avalanche transistor to drive the SRD. HP tended to use a transistor
> driving a slow srd driving a fast srd.
>
I want to keep things simple. PHEMTs are nice but need a lot of fast
gate swing unless followed by an SRD. BJTs almost snap from zero to
saturation withing about 100mV on the drive ramp. I don't really care
about saturation and recovery because the PRF is low.
BJTs are often used for cheap transmitters at UHF or above. Example:
http://www.nxp.com/documents/data_sheet/BFG480W.pdf
Compression is at +20dBm at 2GHz which is pretty much full swing. Some
of the MMIC should also be able to do this but unfortunately have a
different pinout. Northrop-Grumman makes massive (and probably very
expensive) BJT if you need tons of pulse energy for pulsed radar:
http://www.northropgrumman.com/Capabilities/BipolarRFTransistors/Documents/WPTB48F2729Cx.pdf?pdf=Datasheet
--
Regards, Joerg
http://www.analogconsultants.com/
Reply by John Larkin●February 27, 20142014-02-27
On Thu, 27 Feb 2014 17:56:05 -0800, Joerg <invalid@invalid.invalid>
wrote:
>John Larkin wrote:
>> On Thu, 27 Feb 2014 17:59:16 +0100, Gerhard Hoffmann <dk4xp@arcor.de> wrote:
>>
>>> Am 27.02.2014 16:02, schrieb John Larkin:
>>>> Several people still make SRDs. M-pulse, Metelics, MAcom (all SRD makers start
>>>> with "M")
>>>>
>>>> MA44767 and MA44769 are SOT23 distributor items, 50-75 cents range.
>>>>
>>> Ah, found them under varactors @Mouser, at least the MA144769-287T
>>> But 600 ps transition time is not that wonderful anymore, got
>>> half a ns from Fairchild NC7sz04p5x :-)
>>> Nobody escapes the CMOS steamroller!
>>>
>>> thanks, Gerhard
>>
>> The 44769 is rated 150 ps transition time, but they will go a bit faster if you
>> drive them hard.
>>
>> The fastest catalog items are around 25-30 ps.
>>
>> http://www.aeroflex.com/AMS/Metelics/micro-metelics-prods-SRDs-beamlead.cfm
>>
>> Somebody makes some really fast 0402 sized parts, can't remember who.
>>
>> Fast SRDs don't store much charge, so they are hard to drive.
>>
>
><100psec should be doable with a BFP740 and similar ones with the base
>driven sledgehammer-style. Of course, only very few volts allowed at the
>collector.
Have you tried that? My experiments along those lines have been
disappointing.
PHEMTS switch screamingly fast, and the gates are relatively easy to
drive. Good SRD drivers. In the old tek samplers, they usually used an
avalanche transistor to drive the SRD. HP tended to use a transistor
driving a slow srd driving a fast srd.
--
John Larkin Highland Technology, Inc
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Reply by Joerg●February 27, 20142014-02-27
John Larkin wrote:
> On Thu, 27 Feb 2014 17:59:16 +0100, Gerhard Hoffmann <dk4xp@arcor.de> wrote:
>
>> Am 27.02.2014 16:02, schrieb John Larkin:
>>> Several people still make SRDs. M-pulse, Metelics, MAcom (all SRD makers start
>>> with "M")
>>>
>>> MA44767 and MA44769 are SOT23 distributor items, 50-75 cents range.
>>>
>> Ah, found them under varactors @Mouser, at least the MA144769-287T
>> But 600 ps transition time is not that wonderful anymore, got
>> half a ns from Fairchild NC7sz04p5x :-)
>> Nobody escapes the CMOS steamroller!
>>
>> thanks, Gerhard
>
> The 44769 is rated 150 ps transition time, but they will go a bit faster if you
> drive them hard.
>
> The fastest catalog items are around 25-30 ps.
>
> http://www.aeroflex.com/AMS/Metelics/micro-metelics-prods-SRDs-beamlead.cfm
>
> Somebody makes some really fast 0402 sized parts, can't remember who.
>
> Fast SRDs don't store much charge, so they are hard to drive.
>
<100psec should be doable with a BFP740 and similar ones with the base
driven sledgehammer-style. Of course, only very few volts allowed at the
collector.
--
Regards, Joerg
http://www.analogconsultants.com/
Reply by David Platt●February 27, 20142014-02-27
In article <1mkug9pajsm735fpfpt5dn7udujifrmciu@4ax.com>,
John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>Several people still make SRDs. M-pulse, Metelics, MAcom (all SRD makers start
>with "M")
>
>MA44767 and MA44769 are SOT23 distributor items, 50-75 cents range.
Mouser currently has the MACOM MA144769, although they list it as a
varactor diode. It's a buck per, in full-reel quantities... two bucks
or so in small quantity.
Reply by John Larkin●February 27, 20142014-02-27
On Thu, 27 Feb 2014 17:59:16 +0100, Gerhard Hoffmann <dk4xp@arcor.de> wrote:
>Am 27.02.2014 16:02, schrieb John Larkin:
>>
>> Several people still make SRDs. M-pulse, Metelics, MAcom (all SRD makers start
>> with "M")
>>
>> MA44767 and MA44769 are SOT23 distributor items, 50-75 cents range.
>>
>
>Ah, found them under varactors @Mouser, at least the MA144769-287T
>But 600 ps transition time is not that wonderful anymore, got
>half a ns from Fairchild NC7sz04p5x :-)
>Nobody escapes the CMOS steamroller!
>
>thanks, Gerhard
The 44769 is rated 150 ps transition time, but they will go a bit faster if you
drive them hard.
The fastest catalog items are around 25-30 ps.
http://www.aeroflex.com/AMS/Metelics/micro-metelics-prods-SRDs-beamlead.cfm
Somebody makes some really fast 0402 sized parts, can't remember who.
Fast SRDs don't store much charge, so they are hard to drive.
--
John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com
Precision electronic instrumentation
Reply by Gerhard Hoffmann●February 27, 20142014-02-27
Am 27.02.2014 16:02, schrieb John Larkin:
>
> Several people still make SRDs. M-pulse, Metelics, MAcom (all SRD makers start
> with "M")
>
> MA44767 and MA44769 are SOT23 distributor items, 50-75 cents range.
>
Ah, found them under varactors @Mouser, at least the MA144769-287T
But 600 ps transition time is not that wonderful anymore, got
half a ns from Fairchild NC7sz04p5x :-)
Nobody escapes the CMOS steamroller!
thanks, Gerhard
Reply by John Larkin●February 27, 20142014-02-27
On Thu, 27 Feb 2014 13:02:05 +0100, Gerhard Hoffmann <dk4xp@arcor.de> wrote:
>Am 18.02.2014 17:41, schrieb John Larkin:
>
>> https://dl.dropboxusercontent.com/u/53724080/Sampling/Sampler1.JPG
>>
>> That was intended to be a dual-channel sampler, but I never built the one on the
>> right. There's a little ceramic pill SRD in the center of the pattern, fed by
>> the twisted pair from below.
>
>Hi, all,
>
>are the still any SRDs that one can buy?
>Maybe certain PIN diodes that can be abused?
>
>regards, Gerhard
Several people still make SRDs. M-pulse, Metelics, MAcom (all SRD makers start
with "M")
MA44767 and MA44769 are SOT23 distributor items, 50-75 cents range.
--
John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com
Precision electronic instrumentation
Reply by Gerhard Hoffmann●February 27, 20142014-02-27
Am 18.02.2014 17:41, schrieb John Larkin:
> https://dl.dropboxusercontent.com/u/53724080/Sampling/Sampler1.JPG
>
> That was intended to be a dual-channel sampler, but I never built the one on the
> right. There's a little ceramic pill SRD in the center of the pattern, fed by
> the twisted pair from below.
Hi, all,
are the still any SRDs that one can buy?
Maybe certain PIN diodes that can be abused?
regards, Gerhard
Reply by Fred Abse●February 19, 20142014-02-19
On Tue, 18 Feb 2014 13:57:50 -0800, John Larkin wrote:
> I won the Navy Science Cruiser Award at a high-school science fair, and
> the prize was a week in the Navy
Second prize, two weeks?
--
"Design is the reverse of analysis"
(R.D. Middlebrook)
Reply by Fred Abse●February 19, 20142014-02-19
On Tue, 18 Feb 2014 12:37:39 -0800, John Larkin wrote:
> My first airplane flight was in the mil version of the DC-3
C47?
--
"Design is the reverse of analysis"
(R.D. Middlebrook)