#### 24BSNR

##### Junior Member level 2

Hi all,

I've looked through some of the questions and seen some references sourced here. But haven't found a satisfactory intuitive explanation.

I'd like to simulate some AC switched capacitor systems in ltspice, without having spectre/cadence access for pss analysis.

I've seen examples that use a delay line and negative resistance (storistor) to emulate a delay (z^-1/2). And I can build a simulation giving a sinc ac response as I might expect.

In Baker's excellent text on advanced circuits, he describes a comb filter without any negative resistance.

I get that the delay line is just a z^-1 shift of one period in time here, but don't get the negative resistor contribution or how the system translates to transfer function equations or direct analog circuit implementation (esp for larger systems).

I have some references (Allen Hollberg, Sansen, etc). But none really elaborate in such a way I can get an intuitive understanding.

I would really like to get my hands on SWITCAP as every reference seems to utilize it outside of Spectre. But I can't find it anywhere.

Any help is appreciated.

edit. I've attached a (translated) example from

They reference out of print Laker texts, but never really elaborate much on the negative resistance or how these translate to actual

equations (transfer function, 3db etc). I tried to use f3db = 1/2pi10k*1n and similar, but my results are way off from the output 3db.

I can also try f3db = 1/(2*pi*(10k//50)*1n) = 3.2MHz. Brings me closer, but not quite. Other variations trying to calculate net resistance with tline don't seem to come out either.

I've looked through some of the questions and seen some references sourced here. But haven't found a satisfactory intuitive explanation.

I'd like to simulate some AC switched capacitor systems in ltspice, without having spectre/cadence access for pss analysis.

I've seen examples that use a delay line and negative resistance (storistor) to emulate a delay (z^-1/2). And I can build a simulation giving a sinc ac response as I might expect.

In Baker's excellent text on advanced circuits, he describes a comb filter without any negative resistance.

I get that the delay line is just a z^-1 shift of one period in time here, but don't get the negative resistor contribution or how the system translates to transfer function equations or direct analog circuit implementation (esp for larger systems).

I have some references (Allen Hollberg, Sansen, etc). But none really elaborate in such a way I can get an intuitive understanding.

I would really like to get my hands on SWITCAP as every reference seems to utilize it outside of Spectre. But I can't find it anywhere.

Any help is appreciated.

edit. I've attached a (translated) example from

*VLSI Analog Filters: Active RC, OTA-C, and SC ,*Mohan.They reference out of print Laker texts, but never really elaborate much on the negative resistance or how these translate to actual

equations (transfer function, 3db etc). I tried to use f3db = 1/2pi10k*1n and similar, but my results are way off from the output 3db.

I can also try f3db = 1/(2*pi*(10k//50)*1n) = 3.2MHz. Brings me closer, but not quite. Other variations trying to calculate net resistance with tline don't seem to come out either.

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