Mike Perkins wrote:> On 15/02/2014 21:54, Joerg wrote: >> Folks, >> >> After John Larkin sent me SMS7621 Schottky RF diodes I played around >> with them in the lab. While they perform nicely at room temperature >> everything goes to pots at a slightly elevated temperature. At ballpark >> 50C the leakage current is already painfully high for use as a sampler >> diode. >> >> Question: Is there a fast RF diode or sampling diode in a reasonable >> cost range (low single-digit Dollars) with more barrier height? In >> samplers one doesn't care so much about Vf but unfortunately many such >> diodes are marketed as RF detectors where Vf does matter. I guess that's >> why they leak so much when the temps go up. > > If elevated temperature is an issue, why not mount the sampling diodes > on a peltier device? >It was one thought but that greatly increases power consumption, size and complexity. I'd rather use a higher barrier diode which would fix the problem. The Skyworks rep comes out here with some next week. -- Regards, Joerg http://www.analogconsultants.com/
Sampler diodes with more barrier height?
Started by ●February 15, 2014
Reply by ●February 18, 20142014-02-18
Reply by ●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-3C47? -- "Design is the reverse of analysis" (R.D. Middlebrook)
Reply by ●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 NavySecond prize, two weeks? -- "Design is the reverse of analysis" (R.D. Middlebrook)
Reply by ●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 ●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, GerhardSeveral 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 ●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 ●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, GerhardThe 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 ●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 ●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 ●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
