Forums

PIN diode

Started by Unknown October 19, 2021
On 21/10/21 8:23 pm, John S wrote:
> On 10/20/2021 4:41 PM, Clifford Heath wrote: >> On 21/10/21 3:00 am, jlarkin@highlandsniptechnology.com wrote: >>> On Wed, 20 Oct 2021 18:42:53 +0300, Dimiter_Popoff <dp@tgi-sci.com> >>> wrote: >>> >>>> On 10/20/2021 5:20, jlarkin@highlandsniptechnology.com wrote: >>>>> I want to inject a 100 ps test pulse into a 50 ohm transmission line, >>>>> tee-wise, sometimes, from a 25 ohm source. So I need a series switch. >>>>> >>>>> I'd never paid much attention to PIN diodes... they are RF stuff. But >>>>> this one is shocking: >>>>> >>>>> https://www.mouser.com/datasheet/2/249/MADP_008120_12790T-1921620.pdf >>>>> >>>>> 2 ohms on, 0.14 pF off. >>>>> >>>>> And that's packaged. Chip and beam-lead parts are even better. >>>>> >>>>> Of course, in the long-honored RF tradition, there are no DC specs. No >>>>> hint of the forward conduction curve. A tiny note suggests that 10 mA, >>>>> 1 volt might happen. >>>>> >>>>> >>>>> >>>> >>>> Thanks for posting this John. I had been looking for something like >>>> that for a pulse generator I might want to build one day (after >>>> nearly 30 years this day may be coming closer...) and so far I >>>> had seen only parts with 1-2 V reverse voltage ability; this one >>>> seems to handle way more than I need. >>> >>> Yeah, the specs shocked me, after struggling to do this with a >>> schottky. The carrier lifetime could be a problem with long pulses. >>> >>> I love pulse generators. Let me know if I can help. >>> >>> There are all sorts of cheap fungens and scopes and such, but pulse >>> generators are generally still mediocre and expensive. I want to do >>> one myself some day, a really fast version of our DDG. >> >> There is plenty of excitement around the NanoVNA and the TinySA. >> It's time to do a TinyTDR. Bet you'd sell many thousands. If you do >> the pulse gen and the sampler I'll do the rest. >> >> Clifford Heath > > The NanoVNA does TDR. > <https://www.youtube.com/watch?v=9thbTC8-JtA>
Badly, by transforming the frequency/impedance response. Nothing like a real TDR.
On 2021-10-21 13:32, Clifford Heath wrote:
> On 21/10/21 8:23 pm, John S wrote: >> On 10/20/2021 4:41 PM, Clifford Heath wrote: >>> On 21/10/21 3:00 am, jlarkin@highlandsniptechnology.com wrote: >>>> On Wed, 20 Oct 2021 18:42:53 +0300, Dimiter_Popoff <dp@tgi-sci.com> >>>> wrote: >>>> >>>>> On 10/20/2021 5:20, jlarkin@highlandsniptechnology.com wrote: >>>>>> I want to inject a 100 ps test pulse into a 50 ohm transmission line, >>>>>> tee-wise, sometimes, from a 25 ohm source. So I need a series switch. >>>>>> >>>>>> I'd never paid much attention to PIN diodes... they are RF stuff. But >>>>>> this one is shocking: >>>>>> >>>>>> https://www.mouser.com/datasheet/2/249/MADP_008120_12790T-1921620.pdf >>>>>> >>>>>> 2 ohms on, 0.14 pF off. >>>>>> >>>>>> And that's packaged. Chip and beam-lead parts are even better. >>>>>> >>>>>> Of course, in the long-honored RF tradition, there are no DC specs. No >>>>>> hint of the forward conduction curve. A tiny note suggests that 10 mA, >>>>>> 1 volt might happen. >>>>>> >>>>>> >>>>>> >>>>> >>>>> Thanks for posting this John. I had been looking for something like >>>>> that for a pulse generator I might want to build one day (after >>>>> nearly 30 years this day may be coming closer...) and so far I >>>>> had seen only parts with 1-2 V reverse voltage ability; this one >>>>> seems to handle way more than I need. >>>> >>>> Yeah, the specs shocked me, after struggling to do this with a >>>> schottky. The carrier lifetime could be a problem with long pulses. >>>> >>>> I love pulse generators. Let me know if I can help. >>>> >>>> There are all sorts of cheap fungens and scopes and such, but pulse >>>> generators are generally still mediocre and expensive. I want to do >>>> one myself some day, a really fast version of our DDG. >>> >>> There is plenty of excitement around the NanoVNA and the TinySA. >>> It's time to do a TinyTDR. Bet you'd sell many thousands. If you do the pulse gen and the sampler I'll do the rest. >>> >>> Clifford Heath >> >> The NanoVNA does TDR. >> <https://www.youtube.com/watch?v=9thbTC8-JtA> > > Badly, by transforming the frequency/impedance response. > Nothing like a real TDR.
I wonder. I haven't looked at this device in particular, but when I use the FT feature on my HP8753D VNA, the TDR trace is _much_ cleaner than the trace from my Tek S6 sampler and S52 pulser combination. You can't beat a VNA for S/N. Granted, you don't expect HP8753-class quality from a NanoVNA. Jeroen Belleman
jlarkin@highlandsniptechnology.com wrote:
> On Wed, 20 Oct 2021 21:02:16 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> Clifford Heath wrote: >>> On 21/10/21 6:18 am, John Larkin wrote: >>>> On Wed, 20 Oct 2021 20:24:22 +0200, Gerhard Hoffmann <dk4xp@arcor.de> >>>> wrote: >>>> >>>>> Am 20.10.21 um 19:52 schrieb John Larkin: >>>>>> On Wed, 20 Oct 2021 18:05:10 +0200, Gerhard Hoffmann <dk4xp@arcor.de> >>>>>> wrote: >>>>>> >>>>>>> >>>>>>> No. the S-parameter tables give the conditions used for the >>>>>>> measurement. >>>>>> >>>>>> >>>>>> It's the only suggestion of DC operating point in the entire document. >>>>>> Slightly better than nothing, I guess, generous by RF standards. >>>>>> >>>>>> This PIN data sheet has a Vf/If curve, absurdly wrong in the RF >>>>>> tradition. >>>>>> >>>>>> https://www.digikey.com/en/products/detail/infineon-technologies/BA895E6327/12109715 >>>>>> >>>>>> >>>>>> The general tend seems to be high Vf and high reverse leakage. >>>>> >>>>> There is capacitance vs. backward voltage&nbsp; and resistance vs. forward >>>>> current. On page 1.&nbsp; What else could one want? >>>> >>>> Voltage drop vs DC current. Diodes usually specify that, unless they >>>> are "RF" parts. >>>> >>>>> Getting 20 mA forward current through a xyzzy diode is for beginners. >>>> >>>> Beginners with big power supplies. >>> >>> RF switches typically need to stay turned on for the whole cycle. If you >>> want to pass 10mA of RF current, you need 20mA of DC, or more, depending >>> on linearity requirements. >>> >>> Not very familiar with class-A, are you John? RF is almost all class-A. >>> >>> CH >> >> That would be so with a Schottky or very fast junction diode. The point >> of using PIN diodes is that even with a DC current much less than the >> peak RF current, an RF half-cycle transfers only a small portion of the >> stored charge in the junction, so the diode hardly notices.
> > What's extra weird to me is that a regular diode would have a dynamic > resistance around 5 ohms at 5 mA DC. But that Macom PIN diode is about > 2 ohms at 5 mA. > > The mental model of a regular diode with an unusually wide I region > doesn't seem to work.
Ebers-Moll works in the low-frequency limit, where carrier lifetime isn't an issue. Carrier dynamics can do funny things, as you have good reason to know. ;) (*) Cheers Phil Hobbs (*) Grekhov and all that -- 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
whit3rd wrote:
> On Wednesday, October 20, 2021 at 6:02:35 PM UTC-7, Phil Hobbs wrote: > >> > The point >> of using PIN diodes is that even with a DC current much less than the >> peak RF current, an RF half-cycle transfers only a small portion of the >> stored charge in the junction, so the diode hardly notices. > > And it's an important diagnostic tool, to be able to sweep (slowly) the > bias while probing the RF capacitance; it tells you the doping profile of the > junction. 'Hyperabrupt' doping gives the biggest capacitance variation, good > for varactors. >
The doping density is related to the second derivative of C(V), but I've never heard of doing that measurement at forward bias, let alone at RF. 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
On Thu, 21 Oct 2021 10:05:02 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>jlarkin@highlandsniptechnology.com wrote: >> On Wed, 20 Oct 2021 21:02:16 -0400, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> Clifford Heath wrote: >>>> On 21/10/21 6:18 am, John Larkin wrote: >>>>> On Wed, 20 Oct 2021 20:24:22 +0200, Gerhard Hoffmann <dk4xp@arcor.de> >>>>> wrote: >>>>> >>>>>> Am 20.10.21 um 19:52 schrieb John Larkin: >>>>>>> On Wed, 20 Oct 2021 18:05:10 +0200, Gerhard Hoffmann <dk4xp@arcor.de> >>>>>>> wrote: >>>>>>> >>>>>>>> >>>>>>>> No. the S-parameter tables give the conditions used for the >>>>>>>> measurement. >>>>>>> >>>>>>> >>>>>>> It's the only suggestion of DC operating point in the entire document. >>>>>>> Slightly better than nothing, I guess, generous by RF standards. >>>>>>> >>>>>>> This PIN data sheet has a Vf/If curve, absurdly wrong in the RF >>>>>>> tradition. >>>>>>> >>>>>>> https://www.digikey.com/en/products/detail/infineon-technologies/BA895E6327/12109715 >>>>>>> >>>>>>> >>>>>>> The general tend seems to be high Vf and high reverse leakage. >>>>>> >>>>>> There is capacitance vs. backward voltage&#2013266080; and resistance vs. forward >>>>>> current. On page 1.&#2013266080; What else could one want? >>>>> >>>>> Voltage drop vs DC current. Diodes usually specify that, unless they >>>>> are "RF" parts. >>>>> >>>>>> Getting 20 mA forward current through a xyzzy diode is for beginners. >>>>> >>>>> Beginners with big power supplies. >>>> >>>> RF switches typically need to stay turned on for the whole cycle. If you >>>> want to pass 10mA of RF current, you need 20mA of DC, or more, depending >>>> on linearity requirements. >>>> >>>> Not very familiar with class-A, are you John? RF is almost all class-A. >>>> >>>> CH >>> >>> That would be so with a Schottky or very fast junction diode. The point >>> of using PIN diodes is that even with a DC current much less than the >>> peak RF current, an RF half-cycle transfers only a small portion of the >>> stored charge in the junction, so the diode hardly notices. > >> >> What's extra weird to me is that a regular diode would have a dynamic >> resistance around 5 ohms at 5 mA DC. But that Macom PIN diode is about >> 2 ohms at 5 mA. >> >> The mental model of a regular diode with an unusually wide I region >> doesn't seem to work. > >Ebers-Moll works in the low-frequency limit, where carrier lifetime >isn't an issue. Carrier dynamics can do funny things, as you have good >reason to know. ;) (*) > >Cheers > >Phil Hobbs > >(*) Grekhov and all that
Most semiconductor effects were discovered largely by accident, theory later. Diodes, bipolar transistors, SRDs, DSRDs, apparently the tunnel diode. I guess most physics was like that too. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
On Thu, 21 Oct 2021 14:16:02 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

>On 2021-10-21 13:32, Clifford Heath wrote: >> On 21/10/21 8:23 pm, John S wrote: >>> On 10/20/2021 4:41 PM, Clifford Heath wrote: >>>> On 21/10/21 3:00 am, jlarkin@highlandsniptechnology.com wrote: >>>>> On Wed, 20 Oct 2021 18:42:53 +0300, Dimiter_Popoff <dp@tgi-sci.com> >>>>> wrote: >>>>> >>>>>> On 10/20/2021 5:20, jlarkin@highlandsniptechnology.com wrote: >>>>>>> I want to inject a 100 ps test pulse into a 50 ohm transmission line, >>>>>>> tee-wise, sometimes, from a 25 ohm source. So I need a series switch. >>>>>>> >>>>>>> I'd never paid much attention to PIN diodes... they are RF stuff. But >>>>>>> this one is shocking: >>>>>>> >>>>>>> https://www.mouser.com/datasheet/2/249/MADP_008120_12790T-1921620.pdf >>>>>>> >>>>>>> 2 ohms on, 0.14 pF off. >>>>>>> >>>>>>> And that's packaged. Chip and beam-lead parts are even better. >>>>>>> >>>>>>> Of course, in the long-honored RF tradition, there are no DC specs. No >>>>>>> hint of the forward conduction curve. A tiny note suggests that 10 mA, >>>>>>> 1 volt might happen. >>>>>>> >>>>>>> >>>>>>> >>>>>> >>>>>> Thanks for posting this John. I had been looking for something like >>>>>> that for a pulse generator I might want to build one day (after >>>>>> nearly 30 years this day may be coming closer...) and so far I >>>>>> had seen only parts with 1-2 V reverse voltage ability; this one >>>>>> seems to handle way more than I need. >>>>> >>>>> Yeah, the specs shocked me, after struggling to do this with a >>>>> schottky. The carrier lifetime could be a problem with long pulses. >>>>> >>>>> I love pulse generators. Let me know if I can help. >>>>> >>>>> There are all sorts of cheap fungens and scopes and such, but pulse >>>>> generators are generally still mediocre and expensive. I want to do >>>>> one myself some day, a really fast version of our DDG. >>>> >>>> There is plenty of excitement around the NanoVNA and the TinySA. >>>> It's time to do a TinyTDR. Bet you'd sell many thousands. If you do the pulse gen and the sampler I'll do the rest. >>>> >>>> Clifford Heath >>> >>> The NanoVNA does TDR. >>> <https://www.youtube.com/watch?v=9thbTC8-JtA> >> >> Badly, by transforming the frequency/impedance response. >> Nothing like a real TDR. > >I wonder. I haven't looked at this device in particular, but >when I use the FT feature on my HP8753D VNA, the TDR trace is >_much_ cleaner than the trace from my Tek S6 sampler and S52 >pulser combination. You can't beat a VNA for S/N. > >Granted, you don't expect HP8753-class quality from a NanoVNA. > >Jeroen Belleman
Later generation Tek TDR is much better. And you can smooth and signal average to improve s/n if you really need to. A dual-channel SD24 TDR head is a nice combination pulse generator and scope, DC to 20 GHz. Is a VNA tdr realtime? I like to run my finger along a trace and follow the TDR, to locate vias and corners and such. I can also touch things with a pencil and instantly see exactly where features are. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
On Wed, 20 Oct 2021 16:41:57 -0700, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

>fT!
On Wed, 20 Oct 2021 16:41:57 -0700, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

>On Wed, 20 Oct 2021 18:30:45 -0400, legg <legg@nospam.magma.ca> wrote: > >>On Wed, 20 Oct 2021 13:09:01 -0700, John Larkin >><jlarkin@highland_atwork_technology.com> wrote: >> >>>On Wed, 20 Oct 2021 14:50:53 -0400, legg <legg@nospam.magma.ca> wrote: >>> >>>>On Tue, 19 Oct 2021 19:20:04 -0700, jlarkin@highlandsniptechnology.com >>>>wrote: >>>> >>>>>I want to inject a 100 ps test pulse into a 50 ohm transmission line, >>>>>tee-wise, sometimes, from a 25 ohm source. So I need a series switch. >>>>> >>>>>I'd never paid much attention to PIN diodes... they are RF stuff. But >>>>>this one is shocking: >>>>> >>>>>https://www.mouser.com/datasheet/2/249/MADP_008120_12790T-1921620.pdf >>>>> >>>>>2 ohms on, 0.14 pF off. >>>>> >>>>>And that's packaged. Chip and beam-lead parts are even better. >>>>> >>>>>Of course, in the long-honored RF tradition, there are no DC specs. No >>>>>hint of the forward conduction curve. A tiny note suggests that 10 mA, >>>>>1 volt might happen. >>>> >>>>What's so special? >>>> >>>>A simple re-sort of smd marking files by function, voltage and >>>>current, pulls up quite a few similar or superior devices. >>>> >>>>http://ve3ute.ca/query/smd_PIN_V_A_210810E.zip >>>> >>>>RL >>> >>>The amps and volts numbers appear to be abs max, forward current and >>>reverse voltage. That tells nothing about the conduction curve. >>> >>>RF! >> >>You mean the 'R' values . . . ? > >What is the hfe column? Some values seem to be ohms (RF resistance?) >and some are volts and some are in RT's and one is RfT! > >RF!
Yeah, you'd have to clean up column contents to do R or Vf sorting. Not all parts have either. R~Rf forward conduction impedance Vf usually a maximum forwad voltage T - typical. As a quality of the part, whatever was offered in the data sheet is entered into the table. This is a quick tool to get part numbers in the ballpark. RL
On 2021-10-21 18:19, jlarkin@highlandsniptechnology.com wrote:
> On Thu, 21 Oct 2021 14:16:02 +0200, Jeroen Belleman > <jeroen@nospam.please> wrote: > >> On 2021-10-21 13:32, Clifford Heath wrote: >>> On 21/10/21 8:23 pm, John S wrote: >>>> On 10/20/2021 4:41 PM, Clifford Heath wrote: >>>>> On 21/10/21 3:00 am, jlarkin@highlandsniptechnology.com wrote: >>>>>> On Wed, 20 Oct 2021 18:42:53 +0300, Dimiter_Popoff <dp@tgi-sci.com> >>>>>> wrote: >>>>>> >>>>>>> On 10/20/2021 5:20, jlarkin@highlandsniptechnology.com wrote: >>>>>>>> I want to inject a 100 ps test pulse into a 50 ohm transmission line, >>>>>>>> tee-wise, sometimes, from a 25 ohm source. So I need a series switch. >>>>>>>> >>>>>>>> I'd never paid much attention to PIN diodes... they are RF stuff. But >>>>>>>> this one is shocking: >>>>>>>> >>>>>>>> https://www.mouser.com/datasheet/2/249/MADP_008120_12790T-1921620.pdf >>>>>>>> >>>>>>>> 2 ohms on, 0.14 pF off. >>>>>>>> >>>>>>>> And that's packaged. Chip and beam-lead parts are even better. >>>>>>>> >>>>>>>> Of course, in the long-honored RF tradition, there are no DC specs. No >>>>>>>> hint of the forward conduction curve. A tiny note suggests that 10 mA, >>>>>>>> 1 volt might happen. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> >>>>>>> Thanks for posting this John. I had been looking for something like >>>>>>> that for a pulse generator I might want to build one day (after >>>>>>> nearly 30 years this day may be coming closer...) and so far I >>>>>>> had seen only parts with 1-2 V reverse voltage ability; this one >>>>>>> seems to handle way more than I need. >>>>>> >>>>>> Yeah, the specs shocked me, after struggling to do this with a >>>>>> schottky. The carrier lifetime could be a problem with long pulses. >>>>>> >>>>>> I love pulse generators. Let me know if I can help. >>>>>> >>>>>> There are all sorts of cheap fungens and scopes and such, but pulse >>>>>> generators are generally still mediocre and expensive. I want to do >>>>>> one myself some day, a really fast version of our DDG. >>>>> >>>>> There is plenty of excitement around the NanoVNA and the TinySA. >>>>> It's time to do a TinyTDR. Bet you'd sell many thousands. If you do the pulse gen and the sampler I'll do the rest. >>>>> >>>>> Clifford Heath >>>> >>>> The NanoVNA does TDR. >>>> <https://www.youtube.com/watch?v=9thbTC8-JtA> >>> >>> Badly, by transforming the frequency/impedance response. >>> Nothing like a real TDR. >> >> I wonder. I haven't looked at this device in particular, but >> when I use the FT feature on my HP8753D VNA, the TDR trace is >> _much_ cleaner than the trace from my Tek S6 sampler and S52 >> pulser combination. You can't beat a VNA for S/N. >> >> Granted, you don't expect HP8753-class quality from a NanoVNA. >> >> Jeroen Belleman > > Later generation Tek TDR is much better. And you can smooth and signal > average to improve s/n if you really need to. > > A dual-channel SD24 TDR head is a nice combination pulse generator and > scope, DC to 20 GHz. > > Is a VNA tdr realtime? I like to run my finger along a trace and > follow the TDR, to locate vias and corners and such. > > I can also touch things with a pencil and instantly see exactly where > features are.
No, the HP8753 has a pretty wimpy processor, so updates are slow. A real TDR clearly wins out there. It's not so long ago that I realized I can drive the 7T11 sampler time base plug-in with a DAC to control the sweep and read-out the 7S11 sampling head plug-in with an ADC. So I can now read, filter and average TDR traces to my heart's content with a 50 year-old instrument. Jeroen Belleman
On Wed, 20 Oct 2021 16:41:57 -0700, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

>On Wed, 20 Oct 2021 18:30:45 -0400, legg <legg@nospam.magma.ca> wrote: > >>On Wed, 20 Oct 2021 13:09:01 -0700, John Larkin >><jlarkin@highland_atwork_technology.com> wrote: >> >>>On Wed, 20 Oct 2021 14:50:53 -0400, legg <legg@nospam.magma.ca> wrote: >>> >>>>On Tue, 19 Oct 2021 19:20:04 -0700, jlarkin@highlandsniptechnology.com >>>>wrote: >>>> >>>>>I want to inject a 100 ps test pulse into a 50 ohm transmission line, >>>>>tee-wise, sometimes, from a 25 ohm source. So I need a series switch. >>>>> >>>>>I'd never paid much attention to PIN diodes... they are RF stuff. But >>>>>this one is shocking: >>>>> >>>>>https://www.mouser.com/datasheet/2/249/MADP_008120_12790T-1921620.pdf >>>>> >>>>>2 ohms on, 0.14 pF off. >>>>> >>>>>And that's packaged. Chip and beam-lead parts are even better. >>>>> >>>>>Of course, in the long-honored RF tradition, there are no DC specs. No >>>>>hint of the forward conduction curve. A tiny note suggests that 10 mA, >>>>>1 volt might happen. >>>> >>>>What's so special? >>>> >>>>A simple re-sort of smd marking files by function, voltage and >>>>current, pulls up quite a few similar or superior devices. >>>> >>>>http://ve3ute.ca/query/smd_PIN_V_A_210810E.zip >>>> >>>>RL >>> >>>The amps and volts numbers appear to be abs max, forward current and >>>reverse voltage. That tells nothing about the conduction curve. >>> >>>RF! >> >>You mean the 'R' values . . . ? > >What is the hfe column? Some values seem to be ohms (RF resistance?) >and some are volts and some are in RT's and one is RfT! > >RF! > >> >>I'd assumed you were praising C and R specs. You can sort for >>those. They're a start. For a nominal V/I plot, you'd have to >>get the datasheet. > >That was my point. PIN diode data sheets don't seem to have V/I data. > >> >>Nominal plots aren't much use in design, where every part used >>has to work. > >No data at all is better? That's all over RF data sheets.
I don't think a standard PIN data sheet (or diode, for that matter) is going to help you much, if you intend to use <5V as bias. You must be anticipating mV signal levels . . . then why a PIN? RL