r**********0
发帖数: 15 | 1 电路单电源3.3V供电，V-，V+均为1.65V，输出为0V，伴有幅值极小的频率500K左右的
噪声。是发生自激了吗？可能是什么原因呢？电流源用的是高精度电流源可以精确到
1nA.
如果V-=1.24V，V+=0.06V，运放正常工作吗？输出会是怎样？
多谢高手指教 |
c*******l
发帖数: 4801 | 2 这个电路的cross over freq是50k左右，好像
如果你的op-amp输出impedance大的话，比如几k,cross over附近的phase会掉下来，
就没有phase margin了
看看你的output impedance.
【在 r**********0 的大作中提到】
: 电路单电源3.3V供电，V-，V+均为1.65V，输出为0V，伴有幅值极小的频率500K左右的
: 噪声。是发生自激了吗？可能是什么原因呢？电流源用的是高精度电流源可以精确到
: 1nA.
: 如果V-=1.24V，V+=0.06V，运放正常工作吗？输出会是怎样？
: 多谢高手指教
|
f*****0
发帖数: 489 | 3 I always say that Chinese schools should teach students how to ask questions
. you are just articulating as a rock.
"电路单电源3.3V供电，V-，V+均为1.65V，"
what are V- and V+? in your chart, you marked only V+ (the non-inverting
termianl?). You have to remember that what is presumed for you isn't
necessarily presumed by others.
"输出为0V，伴有幅值极小的频率500K左右的噪声。"
like how small is 极小?
"是发生自激了吗？可能是什么原因呢？"
nobody knows for sure, as you there is so much confusion and so limited info.
but it would be very hard for a 50 |
c****s
发帖数: 2487 | 4
这500KHz有点像是charge pump的工作频率啊
如果你这里的V-不是这么产生的算我白说
电压减小后肯定不能“正常”工作了嘛
至于新的工作状态是否可以接受就要另看了
首先得看看输入diff pair的工作点
【在 r**********0 的大作中提到】
: 电路单电源3.3V供电，V-，V+均为1.65V，输出为0V，伴有幅值极小的频率500K左右的
: 噪声。是发生自激了吗？可能是什么原因呢？电流源用的是高精度电流源可以精确到
: 1nA.
: 如果V-=1.24V，V+=0.06V，运放正常工作吗？输出会是怎样？
: 多谢高手指教
|
n******g
发帖数: 662 | 5 What is the GBW of the OPA? Rf and Cf cause a noise gain pole at around 1MHz.
Use a wideband OPA or re design Rf and Cf.
Probably you also should consider the parasitic capacitance and the
impedance of the current source. They also affect the stability of your
circuit. |
n***r
发帖数: 25 | 6 the gain of the amp is not 500K/10. You think the current source impedance
is 0 ohm? LOL. Primary school students in china know that.
Stupid jerk!
;I always say that Chinese schools should teach students how to ask
questions
;. you are just articulating as a rock.
;the gain of the amp is 500k/10=50k x, approaching most opamp's open loop
;gain, if not more.
;
;so for an input differential of 0.06v-(-1.24v)=1.3v, your opamp would have
;clip'd long ago.
;
;at that king of gain, the bandwidth of th
【在 f*****0 的大作中提到】
: I always say that Chinese schools should teach students how to ask questions
: . you are just articulating as a rock.
: "电路单电源3.3V供电，V-，V+均为1.65V，"
: what are V- and V+? in your chart, you marked only V+ (the non-inverting
: termianl?). You have to remember that what is presumed for you isn't
: necessarily presumed by others.
: "输出为0V，伴有幅值极小的频率500K左右的噪声。"
: like how small is 极小?
: "是发生自激了吗？可能是什么原因呢？"
: nobody knows for sure, as you there is so much confusion and so limited info.
|
n***r
发帖数: 25 | 7 I agree with cosmos. it could be charge pump.
It depends what kind of amplifier. Some amplifiers have charge pump
integrated. Some chopper amplifiers may have switches working at the
frequency as well.
It could also be the switching power supply problem.
Seems it's not oscillation. when circuit oscillates, it's usually not small
signal.
Why connecting 10kohm to vin+? You are adding resistor thermal noise to your
circuit. And it's easier to pickup external interference signal.
【在 r**********0 的大作中提到】
: 电路单电源3.3V供电，V-，V+均为1.65V，输出为0V，伴有幅值极小的频率500K左右的
: 噪声。是发生自激了吗？可能是什么原因呢？电流源用的是高精度电流源可以精确到
: 1nA.
: 如果V-=1.24V，V+=0.06V，运放正常工作吗？输出会是怎样？
: 多谢高手指教
|
a*****s
发帖数: 6260 | 8 普通的运放哪里来的电荷泵. 不知道他所谓的很小的500k噪声是怎么来的,
不是把示波器打到最小档看见的吧. 诚挚地建议他把示波器的探头拿起来
放空中悬着, 看还有没有.
small
your
【在 n***r 的大作中提到】
: I agree with cosmos. it could be charge pump.
: It depends what kind of amplifier. Some amplifiers have charge pump
: integrated. Some chopper amplifiers may have switches working at the
: frequency as well.
: It could also be the switching power supply problem.
: Seems it's not oscillation. when circuit oscillates, it's usually not small
: signal.
: Why connecting 10kohm to vin+? You are adding resistor thermal noise to your
: circuit. And it's easier to pickup external interference signal.
|
n***r
发帖数: 25 | 9 Some opAmps do have integrated charge pump in order to have Rail to Rail
input voltage range with no cross-over Vos distortion.
【在 a*****s 的大作中提到】
: 普通的运放哪里来的电荷泵. 不知道他所谓的很小的500k噪声是怎么来的,
: 不是把示波器打到最小档看见的吧. 诚挚地建议他把示波器的探头拿起来
: 放空中悬着, 看还有没有.
:
: small
: your
|
a*****s
发帖数: 6260 | 10 这个只有看他用的到底啥片子了... 照说就算是电荷泵的噪声也该在数据手册里
说明.
【在 n***r 的大作中提到】
: Some opAmps do have integrated charge pump in order to have Rail to Rail
: input voltage range with no cross-over Vos distortion.
|
|
|
c****s
发帖数: 2487 | 11 以我的理解那个电源本身就提供负电压
最简单的办法是直接用示波器看看电源输出
一般charge pump不算成运放的一部分吧
这部分的复杂程度和个头都不小
【在 n***r 的大作中提到】
: Some opAmps do have integrated charge pump in order to have Rail to Rail
: input voltage range with no cross-over Vos distortion.
|
n***r
发帖数: 25 | 12 I am not sure whether charge pump noise is specified or not. One datasheet I
looked before was not specified.
【在 a*****s 的大作中提到】
: 这个只有看他用的到底啥片子了... 照说就算是电荷泵的噪声也该在数据手册里
: 说明.
|
n***r
发帖数: 25 | 13 Please do some google search, you will find some OpAmps with integrated
charge pump. It's not that difficult to integrate using modern CMOS
technology.
【在 c****s 的大作中提到】
: 以我的理解那个电源本身就提供负电压
: 最简单的办法是直接用示波器看看电源输出
: 一般charge pump不算成运放的一部分吧
: 这部分的复杂程度和个头都不小
|
a*****s
发帖数: 6260 | 14 电荷泵本身的噪声不会单列, 但总的噪声是会的. 能有轨到轨的运放
输出噪声不至于那么差.
不过噪声大家都会说跟你的电路和版图大大相关, 云云
I
【在 n***r 的大作中提到】
: I am not sure whether charge pump noise is specified or not. One datasheet I
: looked before was not specified.
|
h********t
发帖数: 555 | 15 嘿嘿，它整天就在这里胡说八道，其实它连基本的电路知识都没有。
have
【在 n***r 的大作中提到】
: the gain of the amp is not 500K/10. You think the current source impedance
: is 0 ohm? LOL. Primary school students in china know that.
: Stupid jerk!
:
: ;I always say that Chinese schools should teach students how to ask
: questions
: ;. you are just articulating as a rock.
: ;the gain of the amp is 500k/10=50k x, approaching most opamp's open loop
: ;gain, if not more.
: ;
|
f*****0
发帖数: 489 | 16
impedance
dumb ass. the signal is a current source (with infinite output
impedance), and the output voltage is always the input current times Rf
(500K), and has nothing to do with source impedance.
Stupid jerk!
【在 n***r 的大作中提到】
: the gain of the amp is not 500K/10. You think the current source impedance
: is 0 ohm? LOL. Primary school students in china know that.
: Stupid jerk!
:
: ;I always say that Chinese schools should teach students how to ask
: questions
: ;. you are just articulating as a rock.
: ;the gain of the amp is 500k/10=50k x, approaching most opamp's open loop
: ;gain, if not more.
: ;
|
f*****0
发帖数: 489 | 17
integrated
why don't you tell us some such opamps that you have used.
【在 n***r 的大作中提到】
: Please do some google search, you will find some OpAmps with integrated
: charge pump. It's not that difficult to integrate using modern CMOS
: technology.
|
n***r
发帖数: 25 | 18 Hahaha. Now you got smart up. It doen's matter whether it's 10 ohm or 100
ohm. It's a transimpedance amplifier.
Question again:
When you analyzed: "Gain of the amp is 500K/10=50k blah..blah...blah...."
Wasn't that stupid?
【在 f*****0 的大作中提到】
:
: integrated
: why don't you tell us some such opamps that you have used.
|
h********t
发帖数: 555 | 19 你前面才说放大器增益是 500K/10， 人家指出你的错误，你又赶快改口说输出等于 输
入电流乘以Rf. 你非但不感谢别人的指教，还咬人一口。我说你脑子有病，你还不承认
。你在网上发帖，图个啥？帮助别人，同时赢得尊重，对吧？其实你连电路基本常识都
没有，一开口就破绽百出，你还不知趣， 经常来这胡说八道，让大家愈发鄙视你，你
这不是犯贱吗？
【在 f*****0 的大作中提到】
:
: integrated
: why don't you tell us some such opamps that you have used.
|
n***r
发帖数: 25 | 20 I haven't used any of such opamps, but I know they exist.
If you could make yourself ARTICULATE, you should search google.com
with "rail to rail amplifier with integrated charge pump"
Why a "smart & ARTICULATE" people like you need to ask me such a question?
【在 f*****0 的大作中提到】
:
: integrated
: why don't you tell us some such opamps that you have used.
|
|
|
n***r
发帖数: 25 | 21 Hotbelmont,
I totally agree with what you said. He made many good points. He is willing
to help people with questions here, which is very good. I shouldn't have
treated him like this.
The problem is that, fku0000, you dont respect other people.
That's the point. Ok, I am done here
【在 h********t 的大作中提到】
: 你前面才说放大器增益是 500K/10， 人家指出你的错误，你又赶快改口说输出等于 输
: 入电流乘以Rf. 你非但不感谢别人的指教，还咬人一口。我说你脑子有病，你还不承认
: 。你在网上发帖，图个啥？帮助别人，同时赢得尊重，对吧？其实你连电路基本常识都
: 没有，一开口就破绽百出，你还不知趣， 经常来这胡说八道，让大家愈发鄙视你，你
: 这不是犯贱吗？
|
h********t
发帖数: 555 | 22 也没觉得它真的是想帮助别人。其实它就是脑子有病，想卖弄卖弄。我觉得可能是因为它在生活中特失败，所以想在网络上找到一点成就感。问题是它水平实在太次，连一些基础知识都没闹明白，嘴巴还很硬。别人如果要纠正它，它就恼羞成怒，象疯狗一样开始开始乱咬人。因为水平太次，而且人品也太差，哦，不对，因为狗品太差，不仅是在这里，而且还在车版，家居生活版, 为人父母版，美国新闻版，也是人人喊打，经常被骂的抱头鼠窜。过去两年，它都被封了十几次了。
willing
【在 n***r 的大作中提到】
: Hotbelmont,
: I totally agree with what you said. He made many good points. He is willing
: to help people with questions here, which is very good. I shouldn't have
: treated him like this.
: The problem is that, fku0000, you dont respect other people.
: That's the point. Ok, I am done here
|
c****s
发帖数: 2487 | 23 这些我都做过，不用google:)
LZ原文里画的图就是直接给运放外接的负电压
其实现在有些搞笑的是我们外人在这里瞎猜
而正主反倒没什么动静，呵呵
【在 n***r 的大作中提到】
: Please do some google search, you will find some OpAmps with integrated
: charge pump. It's not that difficult to integrate using modern CMOS
: technology.
|
c****s
发帖数: 2487 | 24 那个得看具体应用，如果是音频放大，500KHz和高频谐波都无所谓
【在 a*****s 的大作中提到】
: 电荷泵本身的噪声不会单列, 但总的噪声是会的. 能有轨到轨的运放
: 输出噪声不至于那么差.
: 不过噪声大家都会说跟你的电路和版图大大相关, 云云
:
: I
|
f*****0
发帖数: 489 | 25
wow! for someone who hasn't used such an opamp, you sounded like an
expert.
question?
can you tell us which ones you were referring to when you talked about
the datasheet not having noise data from the charge pump?
http://www.google.com/search?
hl=en&q=rail+to+rail+amplifier+with+integrated+charge+pump&btnG=Google+S
earch&aq=f&oq=&aqi=
no, the ADI chip couldn't have possibly been the one used by the
original poster here so you can skip that - I am sure you don't
understand it anyway.
【在 n***r 的大作中提到】
: I haven't used any of such opamps, but I know they exist.
: If you could make yourself ARTICULATE, you should search google.com
: with "rail to rail amplifier with integrated charge pump"
: Why a "smart & ARTICULATE" people like you need to ask me such a question?
|
f*****0
发帖数: 489 | 26
because no one should respect dumbasses.
don't be scared. we are still interested in your identifying that "rail
to rail opamp with integrated charge pump" that you know so well.
【在 n***r 的大作中提到】
: Hotbelmont,
: I totally agree with what you said. He made many good points. He is willing
: to help people with questions here, which is very good. I shouldn't have
: treated him like this.
: The problem is that, fku0000, you dont respect other people.
: That's the point. Ok, I am done here
|
f*****0
发帖数: 489 | 27
100
you have to understand the context under which I made the comment about
the gain. if you don't, re-reading it may help.
the purpose of that exercise is to get some idea about its a/c bandwith.
if you look at the left of the R1 resistor, the circuit is an inverting
amplifier, with the input voltage being I*R1, and the gain being -Rf/R1.
that is a typical process to design an I-V converter using opamps.
that has nothing to do with the signal source's output impedance, which
you implified in y
【在 n***r 的大作中提到】
: Hahaha. Now you got smart up. It doen's matter whether it's 10 ohm or 100
: ohm. It's a transimpedance amplifier.
: Question again:
: When you analyzed: "Gain of the amp is 500K/10=50k blah..blah...blah...."
: Wasn't that stupid?
|
h********t
发帖数: 555 | 28 你连大二的电路基础都没闹明白。你就自娱自乐吧。
【在 f*****0 的大作中提到】
:
: 100
: you have to understand the context under which I made the comment about
: the gain. if you don't, re-reading it may help.
: the purpose of that exercise is to get some idea about its a/c bandwith.
: if you look at the left of the R1 resistor, the circuit is an inverting
: amplifier, with the input voltage being I*R1, and the gain being -Rf/R1.
: that is a typical process to design an I-V converter using opamps.
: that has nothing to do with the signal source's output impedance, which
: you implified in y
|
f*****0
发帖数: 489 | 29
for someone calling itself "hot", you are anything but.
【在 h********t 的大作中提到】
: 你连大二的电路基础都没闹明白。你就自娱自乐吧。
|
n***r
发帖数: 25 | 30 Ok. I'v already wasted too much time on you. This is my last time to teach
you lessons.
;because no one should respect dumbasses.
Guess I dont have to respect you anyway.
I am not an expert. But I am good enough to kick your sorry ass.
You dont know they exist. And you dont want to spend time to do searching.
But you do have time to write long & erroneous articles to showoff yourself.
Here is the link for you dummy. Go figure out the part yourself.
http://electronicdesign.com/Articles/ArticleID
【在 f*****0 的大作中提到】
:
: for someone calling itself "hot", you are anything but.
|
|
|
f*****0
发帖数: 489 | 31
don't worry, we didn't think so (but thank you for that confirmation
anyway) and we knew from the moment you open up your mouth.
searching.
yourself.
that's a nice part, isn't it.
But where did it say that the integrated charge pump runs at 500khz, our
LZ's problem?
stupid jerk.
【在 n***r 的大作中提到】
: Ok. I'v already wasted too much time on you. This is my last time to teach
: you lessons.
:
: ;because no one should respect dumbasses.
: Guess I dont have to respect you anyway.
: I am not an expert. But I am good enough to kick your sorry ass.
: You dont know they exist. And you dont want to spend time to do searching.
: But you do have time to write long & erroneous articles to showoff yourself.
: Here is the link for you dummy. Go figure out the part yourself.
: http://electronicdesign.com/Articles/ArticleID
|
n***r
发帖数: 25 | 32 Let me go over with you again.
;the gain of the amp is 500k/10=50k x, approaching most opamp's open loop
;gain, if not more.
Let's replace the 10 ohm with 0 ohm. Will your inverting amplifier theory
work? will the transimpedance amplifier work? Admit it, you were misled by
the 10ohm resistor then you came up with a wrong AC bandwith analysis.
;at that king of gain, the bandwidth of the opamp is very low, likely <10hz -
;check out the opamp's datasheet.
Wrong! The bandwidth of the Transimpedance
【在 f*****0 的大作中提到】
:
: don't worry, we didn't think so (but thank you for that confirmation
: anyway) and we knew from the moment you open up your mouth.
: searching.
: yourself.
: that's a nice part, isn't it.
: But where did it say that the integrated charge pump runs at 500khz, our
: LZ's problem?
: stupid jerk.
|
n***r
发帖数: 25 | 33 I said charge pump COULD be a problem. Maybe yes maybe no.
I think if you really want to help LZ here. You should ask him what part he
is using. whether there is an intergrated charge pump or chopping switches.
If you want to know what switching frequency the charge pump runs you can
call the company to figure it out. I cant answer all your questions.
However, even I am not a Doctor, I am quite sure that you are infected by
Rabies.
【在 f*****0 的大作中提到】
:
: don't worry, we didn't think so (but thank you for that confirmation
: anyway) and we knew from the moment you open up your mouth.
: searching.
: yourself.
: that's a nice part, isn't it.
: But where did it say that the integrated charge pump runs at 500khz, our
: LZ's problem?
: stupid jerk.
|
n***r
发帖数: 25 | 34 ;"如果V-=1.24V，V+=0.06V，运放正常工作吗？输出会是怎样？"
;
;so for an input differential of 0.06v-(-1.24v)=1.3v, your opamp would have
;clip'd long ago.
I guess LZ want to apply negative voltage to reverse bias photo detector
junction. So that the photo detector will have less capacitance to improve
the TIA response. |
f*****0
发帖数: 489 | 35
you could have a split personality; someone could have pee'd in your
rice bowl; Maybe yes maybe no.
thanks, that's very helpful.
can
then don't come out saying that the 500khz ripple is due to the charge
pump if you don't have a clue how fast it is running.
not to mention that stupid comment about oscillation usually being
large. if you had the faintest clue about opamp oscillation and had seen
it on a scope, you wouldn't have said that.
【在 n***r 的大作中提到】
: I said charge pump COULD be a problem. Maybe yes maybe no.
: I think if you really want to help LZ here. You should ask him what part he
: is using. whether there is an intergrated charge pump or chopping switches.
: If you want to know what switching frequency the charge pump runs you can
: call the company to figure it out. I cant answer all your questions.
: However, even I am not a Doctor, I am quite sure that you are infected by
: Rabies.
|
n***r
发帖数: 25 | 36 ;"如果V-=1.24V，V+=0.06V，运放正常工作吗？输出会是怎样？"
;
;so for an input differential of 0.06v-(-1.24v)=1.3v, your opamp would have
;clip'd long ago.
I guess LZ want to apply negative voltage to reverse bias photo detector
junction. So that the photo detector will have less capacitance to improve
the TIA response.
Seems you should apply V+ > V-, Just to make sure you dont forward bias the
P-N junction. |
r**********0
发帖数: 15 | 37 多谢各位高手的提示，发现500K噪声来自电流源，如果不接入电流源则测不到500K噪声
。另外示波器探头接别的测试点，比如Vdd，Vref，都有很清晰的电压波形，一条直线
，一放到运放输出就有噪声波形并降至“0”，而如果用数字万用表测运放输出会有对
应于电流源变化的正确直流电压输出值。
我单独验证过运放是好的，并且测过Vos不会导致输出端直流偏置到“0”。
请问可能是什么原因导致探头一放上去就会把电压拉下来？Tektronix普通的探头。 |
f*****0
发帖数: 489 | 38
in your circuit, the output should have a dc content of 1/2Vdd because
the opamp is powered by a single rail, and you shouldn't read 0 on the
scope.
a regular DMM shouldn't read out a 500Khz noise so that's OK.
that's never the issue.
the most likely issue is the circuit's output impedance mismatch vs.
that of the probe, or a defective probe. if the signal you are
amplifying is really a high frequency signal, opamp's output impedance
does go up with frequency. but unless you are using some weir
【在 r**********0 的大作中提到】
: 多谢各位高手的提示，发现500K噪声来自电流源，如果不接入电流源则测不到500K噪声
: 。另外示波器探头接别的测试点，比如Vdd，Vref，都有很清晰的电压波形，一条直线
: ，一放到运放输出就有噪声波形并降至“0”，而如果用数字万用表测运放输出会有对
: 应于电流源变化的正确直流电压输出值。
: 我单独验证过运放是好的，并且测过Vos不会导致输出端直流偏置到“0”。
: 请问可能是什么原因导致探头一放上去就会把电压拉下来？Tektronix普通的探头。
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