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Old 19th November 2004, 12:42 PM   #1
Electrons are yellow and more is better!
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Default FDNR Deluxe Active filter

FDNR in active filters (Frequency Dependent Negative Resistor)

I have tried to get info about the very special Frequency Dependent Negative Resistor.... filter but noone here seems to have come close to it, except for a very few.

Some day I thought it would be fun to make a killer active filter. I have no personal need for it but I'm more interested in it in a technical sense.

Specifications (only at idea stage):

Input buffer

1 Mono subchannel, 10-50 Hz, 4th order

2 Bass stereo, 50-250 Hz, 4th order

3 Mid stereo 250-3000 Hz, 4th order

4 Treble, 3000 Hz, 4th order

All filter sections fed via an individual Jung Regulator

All highpass filters with simulated inductors as generalized impedance converters

All lowpass filters with FDNR's

All filters with adjustable gain

All filters configurable as 0-4 th order and all kinds, like Bessel, Butterworth etc.

All filter will have place for 2 resistors in parallel and the caps will also have options for different kinds and sizes.

The pcb will look as my pcb's usually look like, with groundplane and all.

The whole filter will be made of holemounted parts except for opamps which will have a SO08 option.

Time schedule if someone is interested in mid 2005.
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Old 19th November 2004, 05:57 PM   #2
Luke123 is offline Luke123  Canada
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Peranders

Solutions for you for GIC filters:

1) Electronic Filter Design Handbook by Arthur B.Williams and Fred A.Taylor- ISBN 0-07-070434-1

2) You want to deal with the real thing with no money concern ($1500...? FilterShop from LinearX (www.linearx.com). That is something!

3) Use high quality precision inductors with Sallen-Key filters or MFB topologies. Inductors are hard to get and to some extents more performant than you may think. Electronic inductors have some limits. Trade-offs between the two.

Luke
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Old 19th November 2004, 09:15 PM   #3
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Default Re: FDNR Deluxe Active filter

Quote:
Originally posted by peranders
FDNR in active filters (Frequency Dependent Negative Resistor)

I have tried to get info about the very special Frequency Dependent Negative Resistor.... filter but noone here seems to have come close to it, except for a very few.
You can go to Jim Thompson's website -- S.E.D./Schematics -- and take a look at the stuff on filters -- I modeled the gyrators on Multisim -- just make sure that you pull the output from the correct node!

I think that the problem with making the transformations is that a floating inductor was a little difficult to "realize".

http://www.analog-innovations.com/
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Old 20th November 2004, 06:49 AM   #4
Electrons are yellow and more is better!
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Guys, I have no problems to design those filters. I just wondered if somebody had come close to them in real life.
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Old 21st November 2004, 05:17 AM   #5
BrianL is offline BrianL  United States
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There is an old Burr-Brown (now TI) ap-note on FDNRs for
DAC reconstruction filters.

One can use standard RLC topologies and then do a transform
to come up with component values for the FDNR.
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Old 21st November 2004, 07:49 AM   #6
Electrons are yellow and more is better!
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Please, my question isn't about that. See my post above.
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Old 21st November 2004, 03:05 PM   #7
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Quote:
Originally posted by peranders
Please, my question isn't about that. See my post above.
Well, if you wanted to do something really useful you could design an all pass filter with a pga or vga --
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Old 22nd November 2004, 01:21 PM   #8
Electrons are yellow and more is better!
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All pass filter used in combination with what?

OK, I'll continue to think of this highly advanced filter on my own. I'll come back when the idea has left my mind and gone into my Mac.
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Old 22nd November 2004, 01:25 PM   #9
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all pass filters are used to alter the phase relationship of two signals -- thus you can compensate the time alignment of your drivers.

a pga or vga amplifier allows you to tune the phase without changing many R and C values.

i wasn't kidding. it would advance the state of the art -- you could probably even get it published in Elektor or AudioXpress.
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Old 23rd November 2004, 10:21 AM   #10
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peranders,
I am very interested in such an active cross-over circuit.

A couple of years a go i did build the 40Khz DA filter mentioned in earlier threads and discussions.
Since i could not find info on high pass filters with GIC's i did not persuit the active cross-over. Altough it has been in the back of my mind since then.

Are you willing to share that info ? on high- and low-pass GIC and FDNR sections ?


grtz

Simon
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