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WHOA! Negative Capacitor in LowPass

WHOA! Negative Capacitor in LowPass

See...

"NegCapacitor_Used_in_LowPass.png" on the S.E.D/Schematics Page of my website.

Note the phase!

This was whipped up using idealized components... now to go back and do it with OpAmps and see if it behaves. ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

formatting link
| 1962 |

Reply to
Jim Thompson
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Whoa! Again! Fails transient analysis, blows up... dreams of zero-phase dashed :-( ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     |
Reply to
Jim Thompson

Should of just tried a lowpass with C=-1nF without the active elements... that blows up as well.. which should be obvious if one just stops and thinks for one moment:

I = -C*dV/dt Kaboom! ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     |
Reply to
Jim Thompson

If you're just interested in network response, and not practical implememtation, LT Spice is happy to let you use negative r/l/c component values.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin

Yep. PSpice also. But I got so wrapped up in my amusement with the active-element negative capacitor that I failed to check the simple C=-1nF approach... until the active-element approach produced giga-volts when submitted to transient analysis.

(But it'll pass a dotAC analysis... which leads you down the garden path :-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     |
Reply to
Jim Thompson

Amateur. My negative-c circuits make teravolts.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin

Sno-o-o-o-ort ;-)

I have default gmin set at 1n which limits the "kick". ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

             I'm looking for work... see my website. 

      Thinking outside the box to produce elegant solutions.
Reply to
Jim Thompson

Yup, those pesky lower half plane poles. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

Yes ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

             I'm looking for work... see my website. 

     Thinking outside the box... producing elegant solutions.
Reply to
Jim Thompson

There's a schematic floating around of a two op-amp circuit that synthesizes a floating negative inductor; so now one can make an LC ladder filter using all negative elements.

See what it's like to live in the antimatter universe...

Reply to
bitrex

What was it that Phil Hobbs was saying about kids these days? "SPICE Monkeys", I think the phrase is...

Your basic lowpass RC filter:

RC H(s) = -------- s + RC

Make R = 1 ohm and C = -1F, just to make the 'rithmatic easy.

Then

-1 H(s) = ------ s + -1

Which you could do _in your head_ if you remembered the basics.

Gawd. MIT grads and their computers...

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com 

I'm looking for work -- see my website!
Reply to
Tim Wescott

Right half plane?

Reply to
bitrex

Fourier vs two-sided (i.e. bastardized) Laplace (EE version).

Physicists use the opposite Fourier transform sign convention from EEs, but I was using the EE version as a courtesy, since this is SED. ;)

Cheers

Phil Hobbs

Reply to
pcdhobbs

Which is what I discovered while doodling in the waiting room of my wife's back-injury therapist... which evoked my simulating the phase going the other way.

THEN... I did a transient analysis... kaboom! ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

             I'm looking for work... see my website. 

     Thinking outside the box... producing elegant solutions.
Reply to
Jim Thompson

I should be able to make a shock line in Spice, from Ls and -Cs. Gotta try that.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin

If you want it to be stable with a negative capacitance, use a negative resistance, too. That'll fix things up.

Might get cold if you run much power through it, though.

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com 

I'm looking for work -- see my website!
Reply to
Tim Wescott

Leftists would call that "free" energy ?? ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

             I'm looking for work... see my website. 

     Thinking outside the box... producing elegant solutions.
Reply to
Jim Thompson

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