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.matteo

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Posts: 51
Padova, Italy

single-ended to differential conversion
Aug 27^th, 2010, 10:37am

hi everybody,

I'm designing an active single-ended to differential converter.

I designed a resistively loaded fully differential couple with a 50ohm resistor between the gates of the two transistor to match with the measurement equipment. This couple is followed by another fulldiff couple to remove the common mode signal.

However, I've not enough rejection to the common mode signal and my plus and minus signal are very different in amplitude (and phase) at the output of the first couple and they get worse at the end of the second one. :-/

Does anybody has any suggestion about it? or a pointer to some article?

thanks

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carlgrace Senior Member Offline Posts: 231 Berkeley, CA	Re: single-ended to differential conversion Reply #1 - Aug 27^th, 2010, 11:38am What is the speed you are looking to get with this? For board-level single-ended to differential conversion, you can look at using two op amp circuits, one inverting and one non_inverting. Then the difference is the output.
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.matteo Community Member Offline Posts: 51 Padova, Italy	Re: single-ended to differential conversion Reply #2 - Aug 27^th, 2010, 12:08pm 9 to 18Ghz ...
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Paul Community Fellow Offline Posts: 351 Switzerland	Re: single-ended to differential conversion Reply #3 - Aug 28^th, 2010, 11:24pm Hi Matteo, Why don't you use a balun (http://www.odyseus.nildram.co.uk/RFMicrowave_Circuits_Files/Balun%20Design.pdf)?... Also, at these frequencies you may want to take care of impedance matching. Kind Regards Paul
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pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless	Re: single-ended to differential conversion Reply #4 - Aug 29^th, 2010, 3:08am See the followings. http://www.designers-guide.org/Forum/YaBB.pl?num=1278642989/2#2 http://www.designers-guide.org/Forum/YaBB.pl?num=1233236788/1#1 http://www.designers-guide.org/Forum/YaBB.pl?num=1240201234/1#1 http://www.designers-guide.org/Forum/YaBB.pl?num=1255331741/4#4
Back to top	Kita━━━━━━(ﾟ∀ﾟ)━━━━━━ !!!!! http://www7.plala.or.jp/ungeromeppa/flash/kita.html http://www.youtube.com/watch?v=mjIxGh55bMM&feature=related IP Logged

.matteo

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Posts: 51
Padova, Italy

Re: single-ended to differential conversion
Reply #5 - Aug 30^th, 2010, 12:15am

@pancho_hideboo
thanks a lot for your help. are you suggesting me NOT to design an active single-ended to differential converter and to use the setup in ( http://www.designers-guide.org/Forum/YaBB.pl?num=1233236788/1#1 ) to measure the chip?

@Paul
thanks paul, the pdf is really interesting. the idea of the balun is good and we decided to consider it as a very last choice

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rfcooltools.com

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Re: single-ended to differential conversion
Reply #6 - Sep 8^th, 2010, 10:26pm

Hi Matteo,
1. lead lag (LC-CL) network is a simple way to make a differential signal at a range of frequencies.
2. A cascaded set of poly-phase circuits after a single ended gain stage. because you will loose several dB.

If the signal is an LO then the pdf attached patent should give some insights.

http://rfcooltools.com

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6690218_Method_of_performing_duty_cycle_.pdf

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