Homepage - RF Cafe
Webmaster: Kirt Blattenberger | KB3UON | Sitemap | ©1996-2014     Visit RF Cafe on
      Menu below is just a small sample of what is here!          Visit RF Cafe on Facebook Visit RF Cafe on Twitter Visit RF Cafe on LinkedIn
Custom Search
More than 10,000 searchable pages indexed.
•−•  ••−•    −•−•  •−  ••−•  •
RF Cafe Morse Code >Hear It<

PIN diode bias question... - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


bparker
Post subject: PIN diode bias question... Posted: Wed Nov 23, 2005 6:29 am

Lieutenant

Joined: Fri Aug 27, 2004 11:25 am
Posts: 4
Location: Cape Town, R.S.A.
Hi All,


A fundamental question regarding PIN diodes and their biasing – How does one calculate the minimum DC voltage required to ensure that a PIN diode remains OFF in the presence of RF?

In a specific system implementation, where a PIN diode RF switch is used to cold switch 500 W RF pulsed signal, a shunt diode configuration is used. In this existing system a reverse bias of 50V is used to switch the diodes OFF, but it was shown experimentally that the reverse voltage could be dropped as low as 25V before the RF began to bias the diodes ON.

First of all I understand that 500W RF power corresponds to a RF voltage swing of 450Vp-p, if 50 ohm is assumed. This on top of a -50V bias (for switching the diodes OFF) means that the signal is swinging between -275V and +175V, which one would think would bias the diodes ON during the positive cycle. The minority carrier lifetime of the PIN diode however is related to the fact that this does not happen and the diode remains OFF for the complete duration.

The question then remains, what is the relationship between minority carrier lifetime, RF power, frequency and other PIN diode specifications and this minimum reverse bias voltage to ensure that the diodes remain OFF.

Am I missing something obvious? I’ve searched through various application notes and other literature, which somehow always seem to ignore this requirement.


_________________
B.K.P.


Top

Peter Raynald
Post subject: Posted: Wed Nov 23, 2005 11:44 pm

Captain


Joined: Tue Sep 07, 2004 3:09 pm
Posts: 11
Hello BKP,

This is an interesting question.

As I know when used as attenuators, pin diode long minority carrier lifetime drives the hability of the diode to provide good intermodulation caracteristic.

In a two tone intermodulation test the enveloppe being non-constant, I see this also as the hability to resist bias change by the enveloppe modulation.

I wonder if the equations for linearity of a pin diode attenuator in high attenuation condition would be useful... like the one from MACOM or Alpha. You would be using a criterion for extremely low distortion meaning the diode absorbs no power.



Posted  11/12/2012
A Disruptive Web Presence

Custom Search
Over 10,000 pages indexed! (none duped or pirated)

Read About RF Cafe
Webmaster: Kirt Blattenberger
    KB3UON

RF Cafe Software

RF Cascade Workbook
RF Cascade Workbook is a very extensive system cascaded component Excel workbook that includes the standard Gain, NF, IP2, IP3, Psat calculations, input & output VSWR, noise BW, min/max tolerance, DC power cauculations, graphing of all RF parameters, and has a graphical block diagram tool. An extensive User's Guide is also included. - Only $35.
RF system analysis including
frequency conversion & filters

RF & EE Symbols Word
RF Stencils for Visio

Product & Service Directory
Personally Selected Manufacturers
RF Cafe T-Shirts & Mugs

RF Cafe Software

Calculator Workbook
RF Workbench
Smith Chart™ for Visio
Smith Chart™ for Excel
Your RF Cafe Progenitor & Webmaster
Click here to read about RF CafeKirt Blattenberger... single-handedly redefining what an
                                 engineering website should be.

View the YouTube RF Cafe Intro Video Carpe Diem! (Seize the Day!)

5CCG (5th MOB): My USAF radar shop

Airplanes and Rockets: My personal hobby website

Equine Kingdom: My daughter Sally's horse riding website