# Single Ended to Differntial LPF - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

ljoseph
Post subject: Single ended to differntial LPF Posted: Wed Aug 19, 2009 3:02 pm

Captain

Joined: Tue Sep 04, 2007 7:54 am
Posts: 13
Location: Dallas
Hi,
I have calculated the values for a 230 Mhz LPF for single ended configuration with source and load impedance of 100 ohms. I want o convert this filter to differential. How to convert the L and C values from single ended to differential?

Single ended filter values (5 pole butterworth)
L1=30nH
L2=16nH

C1=29pF
C2=27pF
C3=6pF

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Paul Chriss
Post subject: Re: Single ended to differntial LPFPosted: Mon Sep 21, 2009 10:41 pm

Captain

Joined: Sat Mar 04, 2006 10:12 am
Posts: 8
I swear I don't work for them, but I just did a Google Search and found this program that does the job.

http://www.appliedmicrowave.com/Filter1B.htm

Maybe you can downlaod a trial version?

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Alberto
Post subject: Re: Single ended to differntial LPFPosted: Wed Oct 07, 2009 6:05 pm

Captain

Joined: Sun Oct 04, 2009 5:17 pm
Posts: 6
The 4 series inductors (2 for each branch of the differential filter) value will be equal to the single ended value divided by 2. In your case
L1a = 15 nH
L1b = 15 nH
L2a = 8 nH
L2b = 8 nH
Capacitors, instead, will keep their original value:
C1 = 29 pF
C2 = 27 pF
C3 = 6 pF

Best regards,
Alberto

Posted  11/12/2012

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