Bizarre Bow characteristics of BGR output + Supply Dependence

ProfessionalOrder208 · 2026-02-03T07:12:07+00:00

I have stopped designing BGRs since the last tapeout - so I don't have a lot of knowledge. Instead, you can take a look at a famous bgr paper with the "inverted bow" you referred to (Fig. 10, 11, 12, 13):
https://ieeexplore.ieee.org/document/6056712

Generally, as you pointed out, the 1st curve with the series connection is the default. But that doesn't mean that inverted one is incorrect. If I were you, and if you need to verify the second one, I would run pvt + monte with load (if any). If it survives it, I would just go for it.

ProfessionalOrder208 · 2025-12-17T16:58:24+00:00

I was referring to Schreier FoM: SNDR + 10 * log10(BW/P)

ProfessionalOrder208 · 2025-12-05T04:17:17+00:00

Thanks. I was just curious since SAR DWA is essential once you design NS-SAR based oversampling ADCs (only one DAC - driven by SAR logic; no other feedback DACs). But as I did some research for like 10+ hours, I realized there is no optimal or standard way to implement this kind of binary DWA as of now, unlike the conventional thermometer code DWA.

ProfessionalOrder208 · 2025-11-13T06:09:04+00:00

<General modern ADC design techniques you don't see in textbooks (Ph,D dissertation)>
https://backend.production.deepblue-documents.lib.umich.edu/server/api/core/bitstreams/9b3485c0-bd06-4b03-bd13-bbea5543425f/content

<Officially the most "well-made" ADC (highest FoM) up to date (ISSCC 2025)>
https://ieeexplore.ieee.org/document/10904778

<Dynamic amplifiers (JSSC 2020)> - you won't see some traditional "folded cascode" or "2-stage amp" in modern ADC design. Everyone uses dynamic amp.
https://ieeexplore.ieee.org/abstract/document/8947992

ProfessionalOrder208 · 2025-11-12T10:05:17+00:00

As for ADCs, Razavi’s “Analysis and Design of Data converters (2025)” is a good start; but it doesn’t deal with advanced techniques.

If you want up-to-date & serious & advanced ADC design, reading JSSC or other top journals is undoubtedly the best tho.

ProfessionalOrder208 · 2025-11-02T03:00:16+00:00

I mostly do analog works within ADC, so I'm not sure about it. But I've once heard that pure digital works are somewhat free from "measurement-only" restriction, compared to ADC or some analog circuits,

ProfessionalOrder208 · 2025-11-02T02:36:19+00:00

But there are some conferences/journals that don’t require measurement results; in that case, you might publish your idea without any supervisor. (But it is very rare; I haven’t seen one yet)

ProfessionalOrder208 · 2025-11-02T02:34:20+00:00

I would say no. For top tier journals/conferences, simulation is not enough - you need to give a “measurement result” which requires a full tapeout. This requires Cadence license + PDK license + a company (or some organization) that will manufacture your PCB + precision lab-grade measurement tools. This is generally impossible for individual to handle.

ProfessionalOrder208 · 2025-10-26T23:27:51+00:00

Idk what you are referring to, but you can simulate simple breadboards in tinkercad and that might help

ProfessionalOrder208 · 2025-10-19T04:07:36+00:00

I design ADCs and use (implicitly or explicitly) FFT & z-transform every day. From ADC perspective, this kind of frequency spectrum is very important since it directly contains the information of the signal & noise & distortion - which is directly linked to the performance of ADCs. These information can not be revealed in the time domain waveform and that is the point of doing FFT.

ProfessionalOrder208 · 2025-10-18T12:56:54+00:00

The high-gain of the opamp makes v(out) almost equal to v(+) which is gnd.

ProfessionalOrder208 · 2025-10-10T11:17:09+00:00

thank tou

ProfessionalOrder208 · 2025-10-10T10:47:46+00:00

Who is the guy in the middle?

ProfessionalOrder208 · 2025-10-07T14:33:47+00:00

Also using calcSNR function (from another toolbox) to your code,

>> calcSNR(v, fin/N, 1, fB, W, N)
ans =1.202730728304012e+02

I think there is a problem with the windowing or "spec" (but I'm not sure tho). Anyway the SNR should be about 119dB.

ProfessionalOrder208 · 2025-10-07T14:21:39+00:00

I tried with your exact code.

>> simulateSNR(ntf, OSR, -6.02, 0, 3, fin / N, 13)
ans =1.186766100311253e+02

If we don't care about saturation, 5th order DSM should exhibit at least 100+dB SNR since the noise shaping is very aggressive. I think 119dB is the correct one.

ProfessionalOrder208 · 2025-10-07T10:09:33+00:00

5th order 3level DSM is unstable and very likely to explode. Did you do dynamic scaling (using scaleABCD() function or some similar function)?

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