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. -- 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.
PIN diode
Started by ●October 19, 2021
Reply by ●October 20, 20212021-10-20
On 2021-10-20 04:20, 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.DC-wise, it's just a diode. Not too many surprises there. Jeroen Belleman
Reply by ●October 20, 20212021-10-20
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.Not much likelihood of recognizing one if you stumbled over it either, from lack of marking info. RL
Reply by ●October 20, 20212021-10-20
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Reply by ●October 20, 20212021-10-20
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.
Reply by ●October 20, 20212021-10-20
On Wed, 20 Oct 2021 08:29:17 +0200, Jeroen Belleman <jeroen@nospam.please> wrote:>On 2021-10-20 04:20, 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. > >DC-wise, it's just a diode. Not too many surprises there. > >Jeroen BellemanI just found this in my spam folder: https://rfmwblog.com/2021/10/18/why-are-dc-specifications-included-on-rf-device-data-sheets/?utm_source=RFMWSource-Monthly&utm_campaign=20211017-Source&utm_medium=email&utm_term=blog-dc-specs&utm_content=blog This is hilarious, and attempt to answer their question "why take DC test measurements at all?" when all any RF guy needs is S-parameters. I can imagine dozens of diode types. This PIN is probably GaAs. I have +-5 volts available to turn it on and off, but I can imagine having 0/+2.5 from an FPGA, or +-0.8 differential PECL. Its DC curves and tolerances might matter. -- 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.
Reply by ●October 20, 20212021-10-20
On 2021-10-20 17:42, Dimiter_Popoff 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.You do realize that it's not the PIN diode that makes the pulse, right? A pin diode is merely a switch, and not even a very fast one at that. Jeroen Belleman
Reply by ●October 20, 20212021-10-20
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. http://www.highlandtechnology.com/DSS/P500DS.shtml -- 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.
Reply by ●October 20, 20212021-10-20
On 2021-10-20 17:46, jlarkin@highlandsniptechnology.com wrote:> On Wed, 20 Oct 2021 08:29:17 +0200, Jeroen Belleman > <jeroen@nospam.please> wrote: > >> On 2021-10-20 04:20, 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. >> >> DC-wise, it's just a diode. Not too many surprises there. >> >> Jeroen Belleman > > I just found this in my spam folder: > > https://rfmwblog.com/2021/10/18/why-are-dc-specifications-included-on-rf-device-data-sheets/?utm_source=RFMWSource-Monthly&utm_campaign=20211017-Source&utm_medium=email&utm_term=blog-dc-specs&utm_content=blog > > This is hilarious, and attempt to answer their question "why take DC > test measurements at all?" when all any RF guy needs is S-parameters. > > I can imagine dozens of diode types. This PIN is probably GaAs. I have > +-5 volts available to turn it on and off, but I can imagine having > 0/+2.5 from an FPGA, or +-0.8 differential PECL. Its DC curves and > tolerances might matter.Ah, OK! ;-) An RF guy would just apply ten volts through a kOhm and a choke or two, so he doesn't care! Jeroen Belleman
Reply by ●October 20, 20212021-10-20
Am 20.10.21 um 17:59 schrieb Jeroen Belleman:> On 2021-10-20 17:42, Dimiter_Popoff 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.No. the S-parameter tables give the conditions used for the measurement.>> 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. > > You do realize that it's not the PIN diode that makes the pulse, > right? A pin diode is merely a switch, and not even a very fast > one at that.and, for the LTspice fans: spice cannot simulate it. Gerhard
