FDNR in active filters (Frequency Dependent Negative Resistor) - Page 3

peranders · 20th April 2004, 09:22 PM

Is this FDNR topology so rare that NOONE has come close to it? I'll guess I'll have to simulate it when I have got the time.

GaryB · 21st April 2004, 12:49 AM

How about this?

peranders · 21st April 2004, 05:57 AM

This is one way to solve it but "the circuit" is a simulated inductor. The weird FDNR caught my interest so I wanted to use it also. Nobody will see the difference but I will.

moamps · 21st April 2004, 07:57 AM

Quote:

Originally posted by GaryB

Take a look at the PCM63 datasheet: http://focus.ti.com/lit/ds/symlink/pcm63.pdf

Hi,
Complete DAC project with PCM63 and FDNR was published in Elektor 10/92 (German version).
Regards

peranders · 21st April 2004, 08:14 AM

Please, guys, my question now was about high-pass filters and you don't have them in CD players.

phase_accurate · 21st April 2004, 08:31 AM

Peranders wants to build a HIGHpass, so the DAC project wouldn't help him much.

You have to use an inductor to ground in order to get a highpass filter (wheter it is first-order with a series resistor or 2nd order with a series cap). This can be simulated using a gyrator or the well-known simulated inductor as it is used in many EQ circuits.

Both of these are grounded however. But I don't see any reason to use sophisticated circuitry that can be run ungrounded, only to substitute a simple cap.

Regards

Charles

peranders · 21st April 2004, 08:34 AM

Quote:

Originally posted by peranders
I have small plans to make a really cool cross over filter. I had in mind, 2nd, 3rd and 4th order LP sub, LP, BP and HP filter. Super universal with universal charateristics, Chebushev, Butterworth, Bessel (anykind) etc.

It seems that FDNR is a totally unexplored field. Maybe we should explore it for hifi usage?

Since overkill is my brand I thought it would be cool to design a well-made ultra universal filter but this is a rather big project so I'll guess I can't make it this week. Seriously, I have thought about it 10 years now and time to time it pops up in my brain.

The opamps I think of here are AD8620 and OPA2134. The opamps have to be dual (=matched), so have I been told.

moamps · 21st April 2004, 08:34 AM

Quote:

Originally posted by peranders
Please, guys, my questionnow was about high-pass filters and you don't have them in CD players.

Don't be nervous....
Search for "GIC" in browser...You will find something like this......

peranders · 21st April 2004, 08:35 AM

But this isn't a FDNR.

peranders · 21st April 2004, 08:38 AM

Quote:

Originally posted by phase_accurate
But I don't see any reason to use sophisticated circuitry that can be run ungrounded, only to substitute a simple cap.

A possible solution is to use GIC as an inductor but the goal was (if it's possible) to have an all-FDNR filter.

20th April 2004, 09:22 PM	#21
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Is this FDNR topology so rare that NOONE has come close to it? I'll guess I'll have to simulate it when I have got the time. __________________ /Per-Anders (my first name) or P-A as my friends call me Tube Buffered Gainclone in work \|Thread

21st April 2004, 05:57 AM	#23
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	This is one way to solve it but "the circuit" is a simulated inductor. The weird FDNR caught my interest so I wanted to use it also. Nobody will see the difference but I will. __________________ /Per-Anders (my first name) or P-A as my friends call me Tube Buffered Gainclone in work \|Thread

21st April 2004, 08:14 AM	#25
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Please, guys, my question now was about high-pass filters and you don't have them in CD players. __________________ /Per-Anders (my first name) or P-A as my friends call me Tube Buffered Gainclone in work \|Thread

21st April 2004, 08:35 AM	#29
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	But this isn't a FDNR. __________________ /Per-Anders (my first name) or P-A as my friends call me Tube Buffered Gainclone in work \|Thread

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21st April 2004, 08:31 AM	#26
phase_accurate diyAudio Member Join Date: May 2002 Location: Switzerland	Peranders wants to build a HIGHpass, so the DAC project wouldn't help him much. You have to use an inductor to ground in order to get a highpass filter (wheter it is first-order with a series resistor or 2nd order with a series cap). This can be simulated using a gyrator or the well-known simulated inductor as it is used in many EQ circuits. Both of these are grounded however. But I don't see any reason to use sophisticated circuitry that can be run ungrounded, only to substitute a simple cap. Regards Charles

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