Custom Search
Over 10000 Pages Indexed
Your Host
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

Hobby & Fun

Airplanes and Rockets:
My personal hobby website

Equine Kingdom:
My daughter Sally's horse
riding business website -
lots of info

•−•  ••−•    −•−•  •−  ••−•  •
RF Cafe Morse Code >Hear It<

Job Board

About RF Cafe©

RF Cafe E-Mail

How can I match 100K om to 12K om - 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.


cpeter
Post subject: How can I match 100K om to 12K om
Unread postPosted: Wed Mar 09, 2005 11:32 pm
Offline
Lieutenant

Joined: Wed Mar 09, 2005 11:20 pm
Posts: 2
I am doing a design:

AD9854 -> differential & quadrature signal -> 80MHz filter & match network? -> AD8346

And:
output impedance of AD9854: 100k om
input impedance of AD8346: 12k om

how can I design the filter & match circuit?

Thanks.
Peter


Top
Profile

Guest
Post subject: Impedance matching?
Unread postPosted: Sun Mar 13, 2005 10:18 pm

Peter,
Your question leaves out some important information - such as the frequency range involved.

The impedances you cite are only accurate at very low frequencies. There is significant reactance present at any reasonable RF frequency. (There's both bond wire inductance and bonding pad capacitance to ground).

The implication is that you probably don't want to match 100k to 12k, since you really won't have it anyway! Digital-to-Analog converters are often driven into the summing junction of an operational amplifier - which is a "virtual ground". From the classical RF viewpoint, that's weird - but the DAC output is often essentially a current, which must be converted to a voltage.

Check out Analog Devices' application notes on the AD9854 - I'm sure that they don't show the kind of impedance-matching network you're asking for.

Good Luck!


Top


cpeter
Post subject: Thanks.
Unread postPosted: Wed Mar 16, 2005 1:47 am
Offline
Lieutenant

Joined: Wed Mar 09, 2005 11:20 pm
Posts: 2
You answer is very helpful, thanks a lot!
:D







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