Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
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IMS resistors with partial wraparound - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
phpBB would release a version with integrated
sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
Post subject: IMS resistors with partial wraparound
postPosted: Wed Jun 29, 2005 4:12 pm
I am reading about IMS
resistors, that are said to be more suited for microwave performances
than standard SMT resistors.
Does anybody know if it is stricly
a question of wraparound?
For example I saw simulations with
manufacturer's model on ADS comparing kemet resistors and IMS. For 0805
package between 1 and 2 GHz there was a significant slope 1dB on the
attenuation. For the IMS resitors however this slope was minimal.
I am suprised that just this wraparound question would cause such
Anybody experienced the same? Any comments?
Tue Jul 05, 2005 1:08 pm
Wraparound certainly is a big part
of it. A lot depends on the value of the resistor and the intended use.
For large value resistors, the wraparound can add a signficant parallel
capacitance term. For low value resistors, the wraparound can add a
significant series inductive term. The method of attachment can also
be a significant factor.
For example, about 20 years ago I designed
a transimpedance amplifier that used a descrete resistor to set the
transimpedance gain (for a fiber optic receiver application). I use
a non-wraparound resistor (from IMS and others) because the sub-pF capacitance
from the wraparound termination would dramatically affect the bandwidth
(due to the multiplication from the amp).