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
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Below are all of the forum threads, including all
the responses to the original posts.
Post subject: How can I match 100K om to 12K om
postPosted: Wed Mar 09, 2005 11:32 pm
Joined: Wed Mar 09, 2005 11:20 pm
I am doing a design:
AD9854 -> differential & quadrature signal -> 80MHz filter &
match network? -> AD8346
output impedance of AD9854:
input impedance of AD8346: 12k om
how can I design
the filter & match circuit?
Post subject: Impedance matching?
postPosted: Sun Mar 13, 2005 10:18 pm
leaves out some important information - such as the frequency range
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
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.
Post subject: Thanks.
Unread postPosted: Wed Mar 16,
2005 1:47 am
Joined: Wed Mar 09, 2005
You answer is very helpful, thanks a lot!