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请教一个非常简单的问题

请教一个非常简单的问题# EE - 电子工程

G*72010-04-27 07:04

1 楼

目前eBay Tech China, Paypal China, Stubhub China 招聘。
主要为技术岗位，工程师,team leader,PM,Director个级别只为都有。欢迎踊跃投递~
欢迎联系：j*****[email protected] or g********[email protected]。

t*r2010-04-27 07:04

2 楼

我的EB1A,458 timeline(NSC)：
10月5号的Fedx隔夜邮寄/NSC
10月20号的485 RD/receipt number
11月22日的Finger Print/biometric打指纹
1月10日，至今无法在uscis官网查到任何记录和状态(打uscis电话，让我下个月1号再
来电咨询)
-------------------------------------------------
注意事项
------------------------------------------------
1, 我有一个朋友10月3号的RD，今天拿到了EAD和AP(2018年1月10日)
2, 现在看来TSC要比NSC快的不是一点点，看来要注明TSC还是NSC
3, 打指纹是否能walk in取决于local office，建议最好不要walkin
4，出生公证如果丢失别怕，公证处都有备份，你可以free索取一个copy
5，公证处做的出生公证如果不符合要求，可以要求公证处free再做一次
Waiting for next steps:
?/?/?Transferred to NBC
?/?/?Interview notice received
?/?/?Interviewed and approved

i*s2010-04-27 07:04

3 楼

以色列一位摄影师在红海捕捉到月亮水母罕见又漂亮的照片。它们看上去好像外星生物
。37岁摄影师尤祖鲁-马苏达在沙特阿拉伯海岸附近短途旅行时用呼吸管潜泳，拍摄到
月亮水母的这些惊人照片。
马苏达说：“这种水母看上去就像单个细胞，它们拥有指引飘动生活方式的潜意识智力
。我还了解到它们为幼鱼提供避难所。我在许多水母中游动，离它们非常近。它们会碰
到我的手臂或腿，但不会令你感到不快。”
苏达在2小时内不仅观察月亮水母，还和它们同游。这些水母不会刺痛触碰它的人，这
位摄影师才让它们径直游向他，甚至碰到他的手臂。亮水母直径20到25厘米，通过脉动
触须在水中游动。
这位摄影师还看到许多颜色艳丽的鱼、有蓝色斑点的黄貂鱼、海鳝、章鱼、鱿鱼、狮子
鱼、梭鱼和乌龟等海洋动物。（孝文）

n*a2010-04-27 07:04

4 楼

有一个很简单的问题，苦苦思索没有好的办法，各位大侠指点。
问题：关于集成电路设计的，有一个sample信号的电路，对于sample到的模拟电压（DC
），想保持比较长的时间，例如几秒或者更长。如果用一个电容保存的话，随着时间推
进，由于漏电流会使电容的电压逐渐降低，这样时间比较长的话，所要保持的信号就衰
减了。请教有没有一个电路结构能够自动的补偿漏电流的影响？
非常感谢。

G*72010-04-27 07:04

5 楼

春节假期结束，招聘继续，嘿嘿。欢迎各位朋友踊跃投递~

【在 G*******7 的大作中提到】

: 目前eBay Tech China, Paypal China, Stubhub China 招聘。
: 主要为技术岗位，工程师,team leader,PM,Director个级别只为都有。欢迎踊跃投递~
: 欢迎联系：j*****[email protected] or g********[email protected]。

t*r2010-04-27 07:04

6 楼

贡献一个我朋友的timeline：
3/15/2017 485 received
6/15/2017 Finger Print
10/26/2017 Transferred to NBC
12/11/2017 Interview notice received
1/10/2018 Interviewed and approved

h*h2010-04-27 07:04

7 楼

好大

【在 i*****s 的大作中提到】

: 以色列一位摄影师在红海捕捉到月亮水母罕见又漂亮的照片。它们看上去好像外星生物
: 。37岁摄影师尤祖鲁-马苏达在沙特阿拉伯海岸附近短途旅行时用呼吸管潜泳，拍摄到
: 月亮水母的这些惊人照片。
: 马苏达说：“这种水母看上去就像单个细胞，它们拥有指引飘动生活方式的潜意识智力
: 。我还了解到它们为幼鱼提供避难所。我在许多水母中游动，离它们非常近。它们会碰
: 到我的手臂或腿，但不会令你感到不快。”
: 苏达在2小时内不仅观察月亮水母，还和它们同游。这些水母不会刺痛触碰它的人，这
: 位摄影师才让它们径直游向他，甚至碰到他的手臂。亮水母直径20到25厘米，通过脉动
: 触须在水中游动。
: 这位摄影师还看到许多颜色艳丽的鱼、有蓝色斑点的黄貂鱼、海鳝、章鱼、鱿鱼、狮子

s*f2010-04-27 07:04

8 楼

典型的dynamic circuit的load floating问题，加个pmos header，output加个inv，
inv的output连到pmos，那么就能自动charge回来了。
如果我没有理解错楼主的意思的话。

G*72010-04-27 07:04

9 楼

国内JAVA机会，期待各位加入~

t*r2010-04-27 07:04

10 楼

搞一个群专门用来共享485进展的信息互助小组

【在 t*******r 的大作中提到】

: 我的EB1A,458 timeline(NSC)：
: 10月5号的Fedx隔夜邮寄/NSC
: 10月20号的485 RD/receipt number
: 11月22日的Finger Print/biometric打指纹
: 1月10日，至今无法在uscis官网查到任何记录和状态(打uscis电话，让我下个月1号再
: 来电咨询)
: -------------------------------------------------
: 注意事项
: ------------------------------------------------
: 1, 我有一个朋友10月3号的RD，今天拿到了EAD和AP(2018年1月10日)

i*s2010-04-27 07:04

11 楼

h*t2010-04-27 07:04

12 楼

For me, this is not a simple question.
You have to either improve the process and layout to reduce the leakage, or
convert it to digital with ADC and store it in registers, than convert it
back to analog signal with DAC when you need it.
I would love to know who has a better solution.

G*72010-04-27 07:04

13 楼

求贤若渴...

t*r2010-04-27 07:04

14 楼

update:
10.16 RD TSC
11.17 FP
1.8 transfer
1.9 transfer again
1.10,11 EAD

h*h2010-04-27 07:04

15 楼

好大

【在 i*****s 的大作中提到】

h*t2010-04-27 07:04

16 楼

The signal he talked about is analog..

【在 s***f 的大作中提到】

: 典型的dynamic circuit的load floating问题，加个pmos header，output加个inv，
: inv的output连到pmos，那么就能自动charge回来了。
: 如果我没有理解错楼主的意思的话。

G*72010-04-27 07:04

17 楼

:-)

t*r2010-04-27 07:04

18 楼

update
10.3 RD TSC
11.30 Transfer to NBC
12.10 I-131 RFE
No fingerprint Notice

e*s2010-04-27 07:04

19 楼

很一般。

s*f2010-04-27 07:04

20 楼

看漏了"模拟"两字，只做digital的飘过。

【在 h********t 的大作中提到】

: The signal he talked about is analog..

G*72010-04-27 07:04

21 楼

eBay Tech China招聘。
涉及岗位：JAVA 工程师、产品经理、项目经理、Director各个级别职位都有。欢迎踊
跃投递~
欢迎联系：g********[email protected]。

t*r2010-04-27 07:04

22 楼

更新快的都是TSC
10.5 RD TSC
11.6 FP
12.27 to NBC
ap, ead no update

h*t2010-04-27 07:04

23 楼

no problem. you are welcome to float back if you have a better idea.

【在 s***f 的大作中提到】

: 看漏了"模拟"两字，只做digital的飘过。

G*72010-04-27 07:04

24 楼

春节假期结束，招聘继续，嘿嘿。欢迎各位朋友踊跃投递~

【在 G*******7 的大作中提到】

s*12010-04-27 07:04

25 楼

求拉群，刚看见这个帖子
可以重新发一下QR吗？

【在 t*******r 的大作中提到】

: 搞一个群专门用来共享485进展的信息互助小组

c*l2010-04-27 07:04

26 楼

还有个科学实验的办法：
用个时间counter,先calibrate漏电速率，然后反推回去
多烂啊

or

【在 h********t 的大作中提到】

: For me, this is not a simple question.
: You have to either improve the process and layout to reduce the leakage, or
: convert it to digital with ADC and store it in registers, than convert it
: back to analog signal with DAC when you need it.
: I would love to know who has a better solution.

G*72010-04-27 07:04

27 楼

国内JAVA机会，期待各位加入~

u*g2010-04-27 07:04

28 楼

扫WX二维码
[在 songshan311 (song) 的大作中提到：]
:求拉群，刚看见这个帖子
:可以重新发一下QR吗？

h*t2010-04-27 07:04

29 楼

The leakage current could be non-linearly depending on the voltage across the capacitor. It could keep changing with time as the voltage across the capacitor changes with time due to leakage current. The leakage also changes dramatically when ambient temperature changes. If you want to calibrate it, you have to repeat this calibration process from time to time to take care such temperature drift effect. It is quite complicated.

【在 c*******l 的大作中提到】

: 还有个科学实验的办法：
: 用个时间counter,先calibrate漏电速率，然后反推回去
: 多烂啊
:
: or

G*72010-04-27 07:04

30 楼

:-)

p*y2010-04-27 07:04

31 楼

over 100 people, how to join?

s*f2010-04-27 07:04

32 楼

虽然不是做模电的，但是我在想可以用feedback来实现(控制理论)。用一个op amp当
comparator，问题是ref voltage从哪儿来（这个没想明白）。至于如何recharge，这
个和数电一样，即feedback的输出控制一个header pmos。

s*12010-04-27 07:04

33 楼

超过100人了，能加我好友再拉群吗？
WX ID：jiasong278665
谢谢谢谢

n*a2010-04-27 07:04

34 楼

A good point! That is what I am considering now. But I still can not have a
mature schematic to realize it.

【在 s***f 的大作中提到】

: 虽然不是做模电的，但是我在想可以用feedback来实现(控制理论)。用一个op amp当
: comparator，问题是ref voltage从哪儿来（这个没想明白）。至于如何recharge，这
: 个和数电一样，即feedback的输出控制一个header pmos。

p*u2010-04-27 07:04

35 楼

进不去了我的微信是pingyang2013qq 请问可以拉我进去么？

g*t2010-04-27 07:04

36 楼

有所谓的delay phase lock loop,就是你说的类似吧,不过那是数字的.

虽然不是做模电的，但是我在想可以用feedback来实现(控制理论)。用一个op amp当
comparator，问题是ref voltage从哪儿来（这个没想明白）。至于如何recharge，这
个和数电一样，即feedback的输出控制一个header pmos。

【在 s***f 的大作中提到】

g*t2010-04-27 07:04

37 楼

RC filter能行吗?

or

【在 h********t 的大作中提到】

i*n2010-04-27 07:04

38 楼

First you sample, then you hold. it's just a sample and hold circuit.
You can hold the charge in a floating cap, if there's no small resistance to
leak the charge, how could you lose the charge in just a few seconds?
a floating gate in an EPROM can hold the charges for 10 years, why do you
worry about just a few seconds?

h*t2010-04-27 07:04

39 楼

the leakage is primarily due to sampling switches, not the silicon oxide between the capacitor top plate and bottom plate.Most CMOS processes are junction isolated. If you draw a structure of such MOSFET, you will see reverse biased PN junction associated with the MOSFET. The reverse biased PN junction has leakage current, which is exponentially increases with temperature.Even if you use a silicon-oxide isolated process, there is still some leakage current through the channel. The charge migh

【在 i******n 的大作中提到】

: First you sample, then you hold. it's just a sample and hold circuit.
: You can hold the charge in a floating cap, if there's no small resistance to
: leak the charge, how could you lose the charge in just a few seconds?
: a floating gate in an EPROM can hold the charges for 10 years, why do you
: worry about just a few seconds?

g*t2010-04-27 07:04

40 楼

刚才翻了翻书。发现这个问题确实不简单。
hold circuit一般处理的都是比较短时间的hold,
leakage造成的drop的处理已经很复杂。
他原问题要求的hold时间，肯定比一般的
zero order hold之类东西里面的hold时间长不少。
所以我想，最佳方案可能还就是A/D然后把数字存起来。

the leakage is primarily due to sampling switches, not the silicon oxide
between the capacitor top plate and bottom plate.Most CMOS processes are
junction isolated. If you draw a structure of such MOSFET, you will see
reverse biased PN junction associated with the MOSFET. The reverse biased PN
junction has leakage current, which is exponent

【在 h********t 的大作中提到】

: the leakage is primarily due to sampling switches, not the silicon oxide between the capacitor top plate and bottom plate.Most CMOS processes are junction isolated. If you draw a structure of such MOSFET, you will see reverse biased PN junction associated with the MOSFET. The reverse biased PN junction has leakage current, which is exponentially increases with temperature.Even if you use a silicon-oxide isolated process, there is still some leakage current through the channel. The charge migh

i*n2010-04-27 07:04

41 楼

let's say you've got a poor leaking switch with just 200K ohm Roff,
why can't you put 1000 such switch in series, then you get a 200M Roff
switch and you won't have to worry about leakage any more?
OP didn't say if how much die area he can afford to get the job done.

h*t2010-04-27 07:04

42 楼

He does not mention about the die size, that doesn't mean he doesn't care
about die size and cost. why don't you just run some simulation or at least
do some math before you argue? assuming the sampling cap is 10pF. That takes
a significant amount die area. also assuming the channel resistance is 100G
Ohm. is that even much larger than what you proposed of 200Meg Ohm? with
100G Ohm and 10pF, do you math, tell me what is the time constant. if
initially sampled input is 1v, and after that the ana

c*l2010-04-27 07:04

43 楼

听着不现实

【在 i******n 的大作中提到】

: let's say you've got a poor leaking switch with just 200K ohm Roff,
: why can't you put 1000 such switch in series, then you get a 200M Roff
: switch and you won't have to worry about leakage any more?
: OP didn't say if how much die area he can afford to get the job done.

i*n2010-04-27 07:04

44 楼

Wow, I had to admit i didn't do any calculation. Nice explanation.
So, it turns out, it's not an easy question although it looks simple.
May call it "non-volatile analog memory". If anyone can come up with a
solution without going digital, it could be a big deal.

takes a significant amount die area. Also assume the channel resistance is
100G Ohm. is that even much larger than what you proposed of 200Meg Ohm?
with 100G Ohm and 10pF, the time constant = RC=1. if initially the voltage
on the samp

【在 h********t 的大作中提到】

: He does not mention about the die size, that doesn't mean he doesn't care
: about die size and cost. why don't you just run some simulation or at least
: do some math before you argue? assuming the sampling cap is 10pF. That takes
: a significant amount die area. also assuming the channel resistance is 100G
: Ohm. is that even much larger than what you proposed of 200Meg Ohm? with
: 100G Ohm and 10pF, do you math, tell me what is the time constant. if
: initially sampled input is 1v, and after that the ana