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differential low pass filter - RF Cafe Forums
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wolf80
Post subject: differential low pass filter
Unread postPosted:
Mon Nov 15, 2004 1:57 pm
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Joined: Tue Sep
14, 2004 2:46 pm
Posts: 5
Location: San Diego, California
Hey guys, can anyone explain what a differential low pass filter is
used for and how I can design and simulate one? Thank you.
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Post subject: Differential LPF
Unread postPosted: Tue Nov 16, 2004
8:17 pm
Hi!
A differential low pass filter is used on a (usually!)
balanced line, to suppress high frequencies and pass low frequencies.
For example: your telephone line is a differential (balanced) line;
if you wanted for some reason to get rid of all frequencies above 2.8
kHz, you'd use a differential low-pass filter. This would keep the balanced
quality of the line so you wouldn't pick up hum.
The standard
approach is to design a standard LPF, put half of the inductance in
each lead:
----mmm---------
|L
---
---C
|
-------------------
--------mmm------------
|L/2----/
---
---C
|L/2----\
--------mmm------------
Simulation (if you're using SPICE)
requires two transformers - built out of coupled inductors if your version
of SPICE doesn't provide transformers as a basic block.
Good
Luck!
Posted 11/12/2012
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