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Below are all of the forum threads, including all
the responses to the original posts.
Post subject: H21 and S21 phenomenon
Unread postPosted: Thu Apr 28, 2005 3:56 am
Joined: Tue Mar 15, 2005 11:43 pm
Hi All :
I have one big doubt about H21 and S21.
There's a case that for MOSFET device, measured S21 is
too low (<-15dB) range, for 1GHz to 10GHz range. However, the H21 shows larger than 0dB for the same frequency
From H21, the fT is around 3GHz.
I'm not sure whether due to this low fT, the S21 is not there?
I'm not sure whether it's related in anyway.
or maybe there's other reason? and why H21 and S21 shows
I understand that H21 is current gain, while S21 is power gain, but how they are
related to one another?
Hope somebody out there could help me clear my doubt :-)
Unread postPosted: Thu Apr
28, 2005 4:25 am
There are transformations between H-Parameters and S-Parameters, they
can be found in text books.
While H21 is measured in DC and equals to the transistor's hFE or betta, S21 has
its own value, because it is measured under different conditions (50-ohm environment), while H-Parameters are
measured in open/short circuit mixture.
If you can tell in more detail about how your transistor is
connected, then I might be able to help you solve the problem of low gain in the operating frequency.