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Feb 7th, 2023, 2:05pm
1  Design / Analog Design / Re: any analysis paper on stack mos array?
 on: Feb 5th, 2023, 7:49pm 
Started by neoflash | Post by davidshw
This paper may be helpful.

C. Galup-Montoro, M. C. Schneider, and I. J. Loss, ‘Series-parallel association of FET’s for high gain and high frequency applications’, IEEE Journal of Solid-State Circuits, vol. 29, no. 9, pp. 1094–1101, 1994.

2  Modeling / Transmission Lines and Other Distributed Devices / EM simulation with high resistivity substrate in CMOS IC technology
 on: Feb 4th, 2023, 7:56pm 
Started by vlsi_design | Post by vlsi_design
Hi, Is there a way to account for high resistivity substrate in EM simulation software? I am designing an inductor in a CMOS process and using high resistivity substrate to get high Q factor. I have momentum and emx software.

3  Design / Analog Design / Re: any analysis paper on stack mos array?
 on: Jan 24th, 2023, 2:43am 
Started by neoflash | Post by dpalma
Also interested in this topic. A drop here a reference I found helpful

D. Lee and J. Han, «Design Techniques for Area-efficient Two-Stacked Current Sources in Nanometer CMOS Technology», 18th International SoC Design Conference (ISOCC), 2021. doi: 10.1109/ISOCC53507.2021.9613881.

4  Measurements / Phase Noise and Jitter Measurements / Re: Discrepancy between PSD of matlab script and PSD of Spectre
 on: Jan 20th, 2023, 11:51am 
Started by xting108 | Post by cmosbike
Did you find the jitter value from your Verilog-A / matlab script was matched with the guide (9.8 ps?).

5  Simulators / RF Simulators / Re: Phase noise simulation with modulation
 on: Jan 19th, 2023, 4:05am 
Started by cmos_cowboy | Post by Frank Wiedmann

6  Simulators / RF Simulators / Phase noise simulation with modulation
 on: Jan 19th, 2023, 2:27am 
Started by cmos_cowboy | Post by cmos_cowboy
We are trying to run a phase noise simulation in SpectreRF (autonomous oscillator) with some modulation applied (repeatable pattern).
Any hints and tips ?
Thank you.

7  Simulators / Circuit Simulators / Specifying subcircuits for temperature sweep
 on: Jan 18th, 2023, 6:51pm 
Started by kemiyun | Post by kemiyun
Hi, I'm trying to find the best practices for sweeping temperature for some subcircuits of my design while keeping other sections at another constant level. What is the best way of doing this? **EDIT: Forgot to add, I'm trying to do this in spectre, version should be latest, but I will check again tomorrow.

More detailed problem definition: I have a positive temp co current generator that feeds a current into an oscillator that has a negative temp co characteristic so the current generator compensates for the temp variation to a degree. I would like to simulate the temp co effects of these subcircuits on the frequency without separating them or modifying the schematic.

My naive solution that I don't like: I can easily separate these circuits and buffer them or just feed sim output from one to the other. I don't want to do this. I don't have a reason, I just don't like it  ;D . It's not elegant.

Several related solutions I could find from Cadence forums: I've found the following solutions, but these are pretty old. I would like to check whether there are better ways available in newer versions.
I do not like the solution above, because I would have to define it for a lot of devices which is tedious and requires actual parameter changes in the circuit.
I think this solution is closer to what I want but it's a very old response and personally I have a bit of a dislike for MTS stuff (not a rational dislike, I just distrust stuff I don't use as often and my past experience with MTS was problematic in a big project).

I would appreciate any advice on how to do it, or where to look for more info, or any keywords that would put point me in the right direction.

Thank you.

8  Measurements / Phase Noise and Jitter Measurements / Re: Phase Noise through the NTF of VCO
 on: Jan 17th, 2023, 9:19am 
Started by subtr | Post by smlogan
Dear subtr,
Do you still have an interest in your question? If so, I can share an Excel workbook that you can use to place your control voltage noise data (noise versus frequency) and it will plot the resulting output phase noise given the Kvco.


9  Design / Analog Design / Re:  standard deviation of the mismatch for two devices
 on: Jan 16th, 2023, 1:19am 
Started by polyam | Post by A Kumar R
Hi Polyam,

usually PDK document contains a plot of Vth mismatch voltage vs. 1/sqrt(WL), can we find this constant from the plot?.


10  Design / Mixed-Signal Design / Intergtared PGA design problems for delta sigma modulator
 on: Jan 15th, 2023, 7:21pm 
Started by designer_ring | Post by designer_ring
A PGA is required for a high precision DC signal sensing DSM ADC, with function of providing 1~128 signal gain, rail-to-rail input/output, buffering the ADC's SC sampling circuits. Other requirements are also critical: high input impendace, low noise/aliasing, low offset, low power, low INL.

There are generally 2 kinds of strcuture:
1) Resitive Feedback using two OPAs, Buffers are required to driving S/H stage.
2) Capacitive coupled PGA using 1 OPA, input precharge buffers are required to provide high input impendance.

Main challenges:
1) Driving capacibility is conflict with low alasing, anti-aliasing filter is requried before ADC S/H stage, but this will degrade the settling.
2) Varieties of dynamic techniques are used to improve settling without bringing noise problem. e.g. precharge, dynamic filter. BUT the switch's glitch become another serious problem.
3) Even I have solved all problems listed below, the power consumption is relatively high compared with industry benchmark.

I read many IA's papers (Huijsing, e.t.), but these IAs are usually designed for monolithic chip, usually a very large decoupling cap is conencted at the output.

Could anyone help point out any mistake of my understanding above? or provide any inspiration, materials about integrated PGA? Thank you very much!

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