| 主题：仪表放大器：常见的应用问题和解决方案 |
| 在线问答： |
| [问：zw-wu] |
我现在用了AD620与AD8221仪表放大器,但在使用过程中,有时输出会出现一些干扰信号,不知这些仪表放大器怎样才能减小无用信号,提高共模抑制 |
| [答：Forest] |
你可以在输入端之前加入低通滤波器，就可以减少干扰信号了。今天的资料中就有详细的介绍。 |
[2005-12-14 10:38:28] |
| [问：zhangxk] |
在应变片式传感器（Load cell）的放大、转换电路中，要将A/D分辨率提高到19位以上，并且转换速度大于50sps，应选用什么样的芯片组合，或者电路设计中应该考虑哪些因素？ |
| [答：Jing] |
you should pay attentation to the throughput that will be trade off
with your accuracy.You should also pay attentation to your input range
and offset I think you can refer to our AD7730L or AD7799 .If you just
want to use AMP+ADC , you can consider AD8230.It"s a chopper-stable instrument
amplifier. |
[2005-12-14 10:40:23] |
| [问：xianluc] |
如何将设计AD623的输入电路，使AD623单电源+5V供电时，输出信号为0～+5V？ |
| [答：Mariah] |
In single supply condition, the input common mode voltage is very critical
to get the rail to rail output. One good tool to analyze the circuit of
AD623 in single supply condition can be got from the link below:
http://www.analog.com/Analog_Root/static
/techSupport/designTools/interactiveTools
/inamp/inamp.html?inamp=AD623%205V |
[2005-12-14 10:41:13] |
| [问：zzb6503] |
在设计电路时，怎样尽可能使仪表放大器抑制50Hz市电干扰？ |
| [答：Forest] |
AD8221仪表放大器放大器本身就具有很强的共模抑制比，他可以在一定程度上抑制市电的干扰。另外，我们建议在你后续的模拟和数字电路加入带阻滤波器。 |
[2005-12-14 10:41:21] |
| [问：zcw0707] |
在测量微小电流时，需要串入隔离放大器，怎么减小隔离放大器带来的影响？ |
| [答：Yiming] |
如果一定要采用隔离放大器，那么隔离放大器的性能不应该恶化输入信号，也就是选用低噪声的隔离放大器。 |
[2005-12-14 10:42:23] |
| [问：zhangxk] |
如何实现应变片式传感器（Load cell）的交流激励、放大及转换？ |
| [答：Jing] |
You can use ratiomeric method and AC extinction.AC Excitation can be
used to cancel out offset errors, regardless of their source.
AC Excitation here means that 2 sets of readings are taken, with the excitation
voltage to the bridge reversed.
Subtracting the 2 readings cancels out the offset errors, as shown in
the boxed equation.
This technique requires that the readings be stored and subtracted. This
is an effective technique, but if you implemented this with discrete components
you would add more error than you were subtracting. |
[2005-12-14 10:43:12] |
| [问：metrolog] |
现在设计的仪表放大器失调电压的温度系数可达到10nV/K吗？ |
| [答：Steve] |
The lowest drift instrumentation amplifier we have is the AD8230 which
has 50nV/C. The AD8555 has 65nV/C and the AD8553 has 100nV/C. We do not
have any instrumentation amplifier that has 10nV/C of drift at this time |
[2005-12-14 10:43:55] |
| [问：mxslgyb] |
请介绍一下仪表放大器和通用放大器的区别，谢谢！ |
| [答：Forest] |
通常仪表放大器是由三个运放和一些集成的电阻组成，它具有较高的输入电阻，很高的共模抑制比，通常用在信号的最前端进行信号处理。如果用通用放大器组成仪表放大器的形式，由于电阻和运放的不匹配，性能上会有很大的损失，尤其是共模抑制比。 |
[2005-12-14 10:44:55] |
| [问：luoqq] |
模拟数字地要分割吗？ |
| [答：Mariah] |
If your circuit is low frequency and need high accuracy, you need to
separate the analog ground and digital ground. |
[2005-12-14 10:45:29] |
| [问：wangqf2422] |
ADX250芯片用于马达、泵、压缩机监控测量振动指标，如何降低电路信号噪声？如何降低功耗？ |
| [答：Yiming] |
降低噪声的方法：1. 用线性电源，2. 在加速度输出端，用合适的低通滤波器把高频噪声滤掉。
降低功耗的方法：可以降低电源电压，但是这样灵敏度会下降。 |
[2005-12-14 10:46:21] |
| [问：wy56] |
请问：我在进行仪表电路设计时，想将静态工作电压隔离掉，该如何处理？
例如：传感器输出的电压是0.5～1.8V，我想只取用该段电压进行放大及后续处理，该如何做？ |
| [答：Eagle] |
You can use AC couple, but you need to resistors to connect to GND to
provide DC bias. In this way, the high input impedence is lower down by
this resistors. For example, AD8221 differential input impendence is 100G
Ohm, if use 1M Ohm resistors, the input impedence will be less than 1M
Ohm. In this case, we can use a JFET input amplifier to buffer the input
to get high impendence fist, then use AC couple to IIA such as AD8221. |
[2005-12-14 10:46:46] |
| [问：zj2172] |
我公司产品用的传感器采用桥式电路，输出的信号可正可负，但给仪器放大器提供的电源是5V单电源，目前是给仪器放大器的参考电源端提供了一个2.5V的偏置电压，请问这种用法可靠吗，会不会有什么问题，有没有更好的解决方法？谢谢！ |
| [答：Steve] |
Do you mean the sensor can swing below GND? If the sensor output is
between 0V and 5V then this configuration is OK to amplify the output
signal of the sensor. But you cannot condition a bridge that outputs negative
voltages if the instrumentation amplifier is operating on only +5V supplies.
|
[2005-12-14 10:47:17] |
| [问：lijin_as] |
为何仪表放大器不能做到Rail to Rail？ |
| [答：Forest] |
AD623 AD8220是可以做到rail to rail |
[2005-12-14 10:47:42] |
| [问：lwtbenben] |
As we know,AD603 can work at the frequency
of 90MHz.But I want know how can I ruduce the EMI when I design the PCB
board?
Thank you! |
| [答：Steve] |
You can use ferrite beads or a common-mode choke at the inputs of the
AD603. |
[2005-12-14 10:48:00] |
| [问：dxp0715] |
我采集的有用信号是50Hz,但发现经过运放后信号叠加了一些干扰信号，我想在A/D前端加一低通滤波电路，请问设计这个电路时需不需要考虑A/D的采样频率 |
| [答：Jing] |
you can add a low pass filter before A/D. But you should consider your
interested bandwidth and the ADC bandwidth .If you want to get more accuracy,you
can slow down the sample rate. |
[2005-12-14 10:48:10] |
| [问：zw-wu] |
我想问一下,我要用在电能质量监测方面,不知选用什么仪表放大器比较好一点 |
| [答：Eagle] |
I am sorry we do not know exactly the requirement. If you need low cost
and you can use +/-5V power supply, then AD623 is a good choice. |
[2005-12-14 10:48:32] |
| [问：paynewon] |
请问如何设计差动放大器，保证最低的温飘和噪声。 |
| [答：Yiming] |
ADI提供集成的difference Amplifier，比如AD82xx系列 |
[2005-12-14 10:49:19] |
| [问：unaffected] |
why the in-amp constructed by off-chip resistor"s
CMRR performance is worse than integrated in-amps? |
| [答：Steve] |
In-amps need matched resistor ratios for high CMRR. You can get high
performance with external resistors if the resistors are well matched.
This can happen if you buy an integrated resistor array. These arrays
cost more than the amplifier. So if you want low cost and high performance,
you should use a monolithic instrumentation amplifier. |
[2005-12-14 10:50:06] |
| [问：kingway98] |
看了关于AD8221的演讲！
不知道将他用做仪表前端放大的时候，特别是接传感器的时候，对于电源有没有什么特殊要求！ |
| [答：Jing] |
It"s very hard to summarize it in one sentence . It will depend on your
real system requirement.Generally, your power supply should be less ripple
voltage and should be larger than what you will in/output and you should
also reserve enough headroom for your output. if you can use +/- power
supply should be better. |
[2005-12-14 10:50:36] |
| [问：xsj1981
0419] |
为提高拾取电路的灵敏度，应该采取怎么样的方法来减小输入端的噪声干扰 |
| [答：Yiming] |
滤波，选出有用信号 |
[2005-12-14 10:50:58] |
| [问：jimmy
88531] |
仪表放大器中外围器件的精度（如电阻误差）会不会影响测量精度，怎样解决这一问题？ |
| [答：Forest] |
一般仪表放大器需要一个外部电阻来调整增益，电阻的温度系数和内部电阻不匹配的话，会造成精度的影响。AD8221 内部的电阻是负的温度系数。 |
[2005-12-14 10:51:04] |
| [问：lijin_as] |
通常单电源仪表放大器输入电压和电源的差值最小为多少？
当AD623 电源为3.3V时，是否能接受最大2.5V的输入（输出 Vo=1/2 Vin=1.25V）? |
| [答：Mariah] |
It depends on the internal design of the amplifer. For AD623, the input
voltage can be from -Vs-0.15 to +VS-1.5. For 3.3V power supply, it is
-0.15V to 1.8V. |
[2005-12-14 10:52:49] |
| [问：lijin_as] |
能否给一个AD8250数据手册的链接，从ADI网站上找不到 |
| [答：Yiming] |
是预发布版，大概明天3月份有样片。 |
[2005-12-14 10:53:05] |
| [问：mxslgyb] |
我想将±2.5V（±5V、±10可选），0~80Hz模拟信号变成差分信号输出，请问采用ADI的放大器有典型电路吗？ |
| [答：Jing] |
you can use our AD8133/9 to transform signal end signal to differential
signal. You can also use our AD8222 to realize it .Remember to use +/-
power spply with enough headroom. |
[2005-12-14 10:53:12] |
| [问：hzplq] |
对多路微信号（如64路）如何采用仪表放大器 |
| [答：Forest] |
仪表放大器输入阻抗一般都比较高，所以比较适合微信号的处理。对于多路信号的处理，前端先可以采用多路开关（漏电流要考虑），再采用仪表放大器。 |
[2005-12-14 10:53:22] |
| [问：sjmww1127] |
在遇到特别微小的信号时,比如只有微伏大小,这个量比运放的失调都要小,是不是就会被运放淹没,这方面不是很明白,请专家给予讲解. |
| [答：Steve] |
If the input signal is very small, in the uV level, and the offset is
bigger then the signal can be submerged by the offset. But if the input
signal is AC then you may be able to condition this.
Two ways to amplify this type of signal:
use a low offset amplifier like the AD8230 or AD8553
or synchronously modulate the signal and make it an AC signal using switches
or an AD630 and then you can make the small signal AC and condition it. |
[2005-12-14 10:53:47] |
| [问：ljd166] |
我如何准确地计算AI内部前端的两个运放的输出点的电压值？ |
| [答：Jing] |
Vo+=(Vin+ -Vin-).RF/RFG+Vin+
Vo-=V- -(Vin+ -Vin-).RF/RG |
[2005-12-14 10:55:19] |
| [问：T4T4T4] |
运放单电源应用后,信杂比是否会下降很多.我在视频应用中,改单电源后,会下降10多db，应该是有问题的吧？ |
| [答：Eagle] |
Normally it"s caused by the vertual GND (at VCC/2 by 2 resistoers).
Add more decoupling capacitors will be helpful. Use an Voltage reference
such as ADR381 will be better. Please also pay attention to the video
amplitude, it will be clipped if too big (Ie. ADA4862-3, input common
mode range is 1~4V at 5V power supply, if signal plus commone mode level
is lower than 1V or great than 4V, it may be clipped). If you use Rail
to Rail Video amplifier (AD8091, ADA4851), it will be better. |
[2005-12-14 10:57:16] |
| [问：dragon
668899] |
惠斯顿电桥输出2毫伏/v的信号，进行线性放大，实现轨对轨输出，12伏单电源供电，能否提供性价比高的解决方案。 |
| [答：Forest] |
你可以采用AD8221作为信号的前端处理，但如果你比较关心温度漂移的话， AD8230也是不错的选择。另外，采用分立的方法一可以达到高精度，
AD8671是我们高精度的运放，噪声很低，比较适合你12V的电源供电。 |
[2005-12-14 10:57:26] |
| [问：kevinlee] |
你们有在高频上应用的呀？
如何抑制干扰 |
| [答：Yiming] |
对高频段应用，ADI提供差分放大器，比如AD8351, AD8138, AD8139. 一般用滤波的方式抑制干扰。 |
[2005-12-14 10:57:27] |
| [问：qiyu] |
AD8221能工作的最高频率是？ |
| [答：Jing] |
it"s 825KHz @gain=1 typically |
[2005-12-14 10:57:41] |
| [问：benyimi] |
前面你提到匹配电阻引来的共模信号干扰,如果要放大nv高频信号如何处理? |
| [答：Mariah] |
How high is your frequency. For nV signal, you need to select very low
noise amplifier. For example, AD8139 is a very low noise part with differential
input and output. |
[2005-12-14 10:58:19] |
| [问：mxslgyb] |
如何将2.5V或5V单端输入变成差分输入，并且使正负极输入无时差 |
| [答：Jing] |
You can use AD8139/3 to do that |
[2005-12-14 10:58:33] |
| [问：wactd] |
ADI的专家，你们好！我想请问放大器使用单电源供电和双电源供电有什么不同吗？对性能有什么影响？ |
| [答：Steve] |
It depends on whether there is enough headroom. Many instrumentation
amplifiers are designed for +/-15V supplies. You can run them on lower
supplies such as +5V but you will have very little head room. So you cannot
use high gain or you have limited input voltage range. The amplifiers
that are rail to rail are better for use on low voltages such as +3.3V
or +5V.
If you do not have enough headroom, you do not have much input or output
range. So there are some performance limitations.
As long as you have enough head room, you can use the in-amp in single
or dual supply. |
[2005-12-14 10:59:12] |
| [问：motaiping] |
仪表放大器的差分输入,和传感器配合使用时,如何设定输入偏置电路?电阻数值如何选取? |
| [答：Forest] |
采用仪表放大器的偏置电路，一般由你的供电电源来决定，推荐你选取VCC/2。电阻值由你需要的放大倍数来决定。 |
[2005-12-14 10:59:15] |
| [问：ljd166] |
如何计算仪放内部的BUFER，A1，A2两个运放的输出电压？ |
| [答：Jing] |
A1 output Vo+=(Vin+-Vin-)RF/RG+Vin+
A2 output Vo-=V--(Vin+-Vin-)RF/RG |
[2005-12-14 10:59:54] |
| [问：shu_chen] |
我想问一下，如果我们需要对信号加入Dither以改善ADC的性能，在仪表放大器或者差分放大器中，应该如何引入比较合适？ |
| [答：Yiming] |
加入diter能够提高SFDR性能，但是降低了SNR。详见AN-410 |
[2005-12-14 11:01:06] |
| [问：xsj19810419] |
如何输入保护？ |
| [答：Eagle] |
We can use Protection Diode to protect the input, but need pay attentaion
to the impendence. Some device (such as AD629, +/-270V common mode range)
can work at high common mode voltage itself. |
[2005-12-14 11:01:47] |
| [问：motaiping] |
仪表放大器和传感器配合使用时,如何进行调零? |
| [答：Forest] |
仪表放大器一般由一个REF管脚，采用不同的DC电压，可以调整输出的直流电平。我们建议在软件中进行调零，这样比较灵活。 |
[2005-12-14 11:02:23] |
| [问：Jeff.Liu] |
请问：AD8221仪表运放能识别放大的电压信号的最下限是多少？ |
| [答：Mariah] |
It depends on the noise performance of the amplifier. Otherwise, your
signal will be submerged by the noise of the amplifier. |
[2005-12-14 11:03:03] |
| [问：motaiping] |
AD8221的输入共模电压范围有多高?它的大小对仪表放大器的性能有何影响? |
| [答：Jing] |
it"s -Vs+2 and +vs-1.2. It"s not correlate with the performance of IN-AMP.
But you should combine it with your gain,output range etc. |
[2005-12-14 11:03:13] |
| [问：seawolf0718] |
请问如果在单电源的情况下,在REF端加一个直流偏置,那么输出是不是VIN*GAIN+VREF?? |
| [答：Forest] |
没错，不过你要考虑你所加的直流偏置的驱动能力。 |
[2005-12-14 11:03:23] |
| [问：huaqun] |
在ECG检测中,第一级增益一般设置为多少? |
| [答：Wenshuai] |
第一级增益的大小受限于仪表放大器的动态范围和电极极化电压差。一般需要考虑极化电压差为300mV.所以如果用AD8221,供电电压为+/-3.3V,那么放大倍数在6倍左右。如果用AD8220，因为是轨到轨输出，所以放大倍数会必AD8821大。更具体讨论可以发邮件到china.support@analog.com. |
[2005-12-14 11:03:41] |
| [问：myrolite] |
仪表放大器的RF滤波器元件参数的选择有些什么原则?有计算方法吗? |
| [答：Yiming] |
请参见ADI仪表放大器应用指南RFI一节 |
[2005-12-14 11:04:41] |
| [问：qiyu] |
AD82系列那种芯片可工作于30M以上？ |
| [答：Yiming] |
请用AD8138,AD8139, AD8351... |
[2005-12-14 11:05:37] |
| [问：Jeff.Liu] |
1.>仪表运放主要适于处理哪些信号（电压，电流，微小信号）？
2.〉仪表运放与普通运放相比有哪些优缺点？
3.〉我现在要处理放大一10UV以下的电压信号，能直接用仪表运放吗？ |
| [答：Mariah] |
1. Voltage, current, small signal should be OK for IN-AMP.
2. In-amp has large input impedance, large CMRR and it features differential
input.
3. Yes, you can. |
[2005-12-14 11:05:43] |
| [问：ljd166] |
仪表放大器的输入端是否要考虑阻抗匹配？是否也要像运放一样匹配？ |
| [答：Mariah] |
I don"t know what kind of impedance matching you refer to. In-amp has
very large input impedance and small output impedance. |
[2005-12-14 11:06:50] |
| [问：motaiping] |
ADI的单电源仪表放大器有那些型号?在应用时直流输出电平如何精确地调整到电源的一半? |
| [答：Jing] |
We have lots of this kind of IN-AMP such as AD8221,AD623/7/9,AD8222,AD8220,AD8250.
You should terminate the REF pin to the middle of your power supply .
But you should use a low impedence output voltage to bias the REF pin.
For example if you use 0-5V power supply,you can use a 2.5V reference
followed with a op-amp(gain=) to drive the REF pin. |
[2005-12-14 11:06:51] |
| [问：ynh] |
使用多个ＰＧＡ串联后，带宽是否降低？压摆率是否变低，和噪声是否按指数增大 |
| [答：Steve] |
The slowest PGA will influence your bandwidth and slew rate. So for
example if you have 2 PGAs with 10MHz (30V/us) and 1 PGA with 1MHz (1V/us),
your bandwidth and slew will be limited to the 1MHz (1V/us) PGA.
Noise will increase. If you have 3 PGAs
PGA_A with 10nV/rtHz then PGA_B with 10nV/rtHz and PGA_C with 10nV/rtHz
and all the PGA are at a gain of G1, G2 and G3, then referred to input
you will have
((((((10nV/rtHz*G1)^2 + 10nV/rtHz)*G2)^2 + 10nV/rtHz)*G3)^2)/(G1*G2*G3)
Noise is summed by its root sum square. |
[2005-12-14 11:06:56] |
| [问：xsj19810419] |
如何有效解决仪表放大器内存在的潜在射频整流问题 |
| [答：Steve] |
You can build an RFI filter at the input. There is an applicatio note,
AN671.
It is also important to keep the inputs as balanced as possible so that
most of the signal is common-mode.
You can also use ferrite beads or common-mode chokes (inductors) to stop
the signal before it reaches the in-amp. |
[2005-12-14 11:09:08] |
| [问：Jeff.Liu] |
现在要放大一5UV的电压信号，能直接用AD8221吗？ |
| [答：Jing] |
I think you can"t. Because the offset voltage of AD8221 is large than
5uV. For this kind of application you can use a chop amplifier such as
AD8628,AD8230 |
[2005-12-14 11:10:20] |
| [问：Guozhong] |
我看了一些App. Note了解了如何在single surpply时放大,但是滤波怎么做<可不可以? |
| [答：Yiming] |
单电源应用时可以做滤波。 |
[2005-12-14 11:10:20] |
| [问：mxslgyb] |
what"s meaning "Rail to Rail"? Thank you! |
| [答：Wenshuai] |
轨到轨，也就是输入或输出的范围与供电电压的靠近程度。一般轨到轨输入/输出会跟供电电压很靠近，大约可以到10mV左右。 |
[2005-12-14 11:10:59] |
| [问：unaffected] |
why not in-amp use differential output? This
can make CMRR larger. |
| [答：Steve] |
Yes. You can use differential outputs with an in-amp. The AD8221"s data
sheet shows how you can make a differential output, Figure 51. We will
also have a new in-amp, the AD8222 which can be configured for differential
outputs.
Most of the applications in the market ask for single ended outputs that
is why most of the in-amps have single ended outputs. But, we show in
the data sheet and in some articles how to make a differential output. |
[2005-12-14 11:11:25] |
| [问：eargle] |
我在设计ECG的电路,请问AD620对RF的干扰在弱信号采集采用图示的电路可能会有多大改善 |
| [答：Mariah] |
使用如幻灯片29页图所示电路和0.01微法的电容 ，–3 dB的差分信号带宽约为1900Hz。增益为5时，采用1V p-p的应用信号，在10
Hz~20 MHz的频率上，测得电路的输入端直流偏移的漂移小于6微伏。在单位增益的情况下，没有直流偏移的漂移。 |
[2005-12-14 11:11:52] |
| [问：ljd166] |
我们选择了AD623，但是如何解决温漂问题，除了选择低温漂的仪放，有没有简单的方法消除温漂 |
| [答：Eagle] |
(1)Please check if you can use AD623BR. B grade has lower temperature
drift.
200 mV Max Input Offset Voltage (AD623A)
2 mV/"C Max Input Offset Drift (AD623A)
100 mV Max Input Offset Voltage (AD623B)
1 mV/"C Max Input Offset Drift (AD623B)
(2)Cnsider other parts such as AD8221BR (not pin to pin)
.25 μV max input offset voltage
0.3 μV/°C max input offset drift.
(3)Input offset drift will be different with different gain.
(4)Lower down other device"s temperature drift will also help to lower
down the system temperature drift. Choose low drift resistor if you have
serial input resistors for protection purpose. |
[2005-12-14 11:12:39] |
| [问：zcw0707] |
如何用运放精确平移直流电位，比如从8V移到2V，但这个8V是变化的，6V是确定的。 |
| [答：Yiming] |
请检查一下你的问题。谢谢 |
[2005-12-14 11:13:34] |
| [问：都市劣人] |
基于成本考虑，用3个通用放大器搭仪用放大器是否合适？ |
| [答：Mariah] |
Yes, if cost is the most concern. |
[2005-12-14 11:13:58] |
| [问：gostray] |
我把微弱信号用AD8304放大后,当与计算机控制板接上后发现其噪声变大,不知是什么原因?是否换用其它仪表放大器会有好处? |
| [答：Jing] |
It"s very hard to clearify it what"s wrong with it.Because you just
provide us a little information. In fact,if you
use AD8304 to interface with a photo diode,it"s a good selection, the
optical power could be less than -70dbm. I think you should pay attentaion
to the bias circuit of AD8304. please call 800 810 1742 to give us more
information. |
[2005-12-14 11:14:05] |
| [问：hugoliang] |
仪器放大器与普通运放的区别.谢谢 |
| [答：Forest] |
仪表放大器是由三个运放，和一些集成的电阻组成，具有比较高的输入阻抗，和很高的共模抑制比。普通运放要组成仪表放大器的话，由于运放和电阻的不匹配，会有很多性能的损失。 |
[2005-12-14 11:14:29] |
| [问：peng-kai] |
原先ADI公司的AD620运放都作为了医疗生物电放大处理的典范，现在，ADI公司又推出的取代芯片在这方面的处理上是否增加了更好的或优于以前的芯片的方法或其它呢，请列举！ |
| [答：Forest] |
AD8221 就是比较好的新的仪表放大器，他的输入阻抗，共模抑制比都有很大的提高。 |
[2005-12-14 11:15:47] |
| [问：T4T4T4] |
仪表放大器的输入级在PCB布局时应要注意什么问题,才能有良好的噪音性能? |
| [答：Steve] |
Yes. You should be aware of what size resistors you use at the inputs.
Use wide traces at the supply pins and use decouple caps. Sometimes noise
from the power supplies can cause spurs to show up at the in-amp. |
[2005-12-14 11:16:30] |
| [问：jacklee2008] |
如何从仪放的输入电压\电流噪声的指标来计算出要测量的微弱信号的最小值? 与普通运放有区别吗? |
| [答：Mariah] |
We recommend you to read the reference manual "Designers_Guide_To_In-Amps_2edition".
There should be very detailed calculation in it. The book can be downloaded
from the website. |
[2005-12-14 11:17:04] |
| [问：hyjlm] |
能否给出一个仪表用的长时间积分电路?选用什么放大器?AD的高输入崭波自稳零器件有什么型号? |
| [答：Eagle] |
If you need long time in intergration, please choose low bias amplifiers
such as AD8610. Also choose low leakage capacitor.
AD8551/52/54, AD8628 are good chope auto zero amplifiers. AD8555 can adjust
gain. |
[2005-12-14 11:17:41] |
| [问：myrolite] |
仪表放大器的输入端是否需要进行保护?如何进行? |
| [答：Jing] |
Sometimes you should add a input protection if your input common mode
voltage could be larger than the IN-AMP common mode voltage. You could
add shortkey diode or ues resistor divider or use voltage bias circuit
to do that. |
[2005-12-14 11:17:52] |
| [问：zhangxk] |
ADI是否提供应用设计中的技术解决方案？ |
| [答：Mariah] |
What kind of the application? You can contact the local office to know
more information of the solution related to your application. |
[2005-12-14 11:17:57] |
| [问：wz623] |
医疗应用中的所谓“右腿驱动”电路如何设计，就是从INAMP的RG处引出到人体参考电极的提高CMRR的电路。 |
| [答：Mariah] |
You can find the righ leg driver circuit in the datasheet of AD620 and
AD8221. |
[2005-12-14 11:18:25] |
| [问：waterbird] |
放大器的接地处理是相当复杂的，对于高精密仪表放大器，是否对电源地平面的铺设有特别设计要求？ |
| [答：Jing] |
Of course , you should pay attentation to the granding issue. You can
use a ground layer to terminate the AGND and DGND . somethimes you should
also use a guard ring to protect the input signal of the AMP. It"s a big
topic for your question and I can"t interprete it very clear here.Please
call 800 810 1742 for more information. |
[2005-12-14 11:22:03] |
| [问：ljd166] |
我们选用了AD623在16BIT的AD采样，是否ADI可以推荐一些详细的PCB LAYOUT的资料给我们，或者推荐一些相应的书籍，资料？ |
| [答：Mariah] |
AD623 is not very good for 16 bits system in terms of the noise performance.
We recommend you to use AD8221. |
[2005-12-14 11:22:30] |
| [问：singer533] |
目前的仪用放大器最高精度可达多少? |
| [答：Mariah] |
What accuracy spec do you mean? Offset? Noise? |
[2005-12-14 11:23:18] |
| [问：mxslgyb] |
How can I make the differential input to single
output? |
| [答：Steve] |
To make a differential input to a single ended output, use an in-amp,
such as the AD8221, AD623, AD620. It takes a differential input and outputs
a single ended output. |
[2005-12-14 11:23:57] |
| [问：wangqf2422] |
AD745作为（水听器）前置放大器使用为降低功耗，采用-5V~+5V供电对于放大信号有什么影响？输入阻抗过高比如大于500兆欧姆，可以么？如何消除前置放大电路产生的噪声？ |
| [答：Yiming] |
最低工作电压为+/-4.8V，所以可以工作在+/-5V.这样输入处处信号的范围变小。AD745的差分如入阻抗为10Gohm，远大于0.5Gohm。请用滤波的方法滤除噪声。 |
[2005-12-14 11:24:38] |
| [问：adlion] |
如何解决仪表放大器在线路应用中的抗干扰问题？ |
| [答：Jing] |
you can use guard ring to protect the input signal of the AMP. You can
also refer to our presentation to realise the RFI filter (page 29). Of
course, you should also pay attentation to you power supply. |
[2005-12-14 11:24:48] |
| [问：tjqytg] |
溶解氧和ad620放大器应当如何连接,连接时应当注意什么问题? |
| [答：Eagle] |
Normally use differential lines to +Vin and -Vin of AD620, need with
shielding to connect to GND. It will be better if you use AD8221 because
AD8221"s CMRR can works at high frequency (10KHz), it will be very helpful
to remove some higher frequence common mode interference. If you use a
very small package or low power package IIA (Such as AD8220,MSOP package,
±2.5V or +5 V power supply, 700uA power) and a low power ADC (Such as
AD7680, 16bit, 3 mW typ at 100 kSPS with 2.5 V supply), then you can transmitter
data digitally. This will help to put the IIA and ADC very near to sensor
and give best performance. |
[2005-12-14 11:25:36] |
| [问：ljd166] |
如何解决仪表放大器的温漂？有没有一些方法或典型的应用电路？ |
| [答：Mariah] |
The temp drift depends on the performance of the in-amp itself. So there
is little things you can do to improve the temp drift. From your side,
you should select low drift in-amp. And for the resistors in your circuit,
you should select low drip resistors also. |
[2005-12-14 11:25:54] |
| [问：ljd166] |
如何得到仪放内部各个工作点的电压计算公式，以方便我们计算输入信号的范围？ |
| [答：Jing] |
buffer A1 output: VO+=(V+ -V-)RF/RG +V+
buffer A2 output: VO-=V- -(V+ -V-)RF/RG |
[2005-12-14 11:26:23] |
| [问：pepjin] |
在AD8221的输入端需要怎样设计滤波器才能最大幅度降低噪声而又得到快速的响应时间? |
| [答：Jing] |
please refer to page 24,27,29 of the presentation for your question. |
[2005-12-14 11:27:41] |
| [问：tyjiaduo] |
怎样解决线性差的问题 |
| [答：Eagle] |
1. Choose a good amplifier, such as AD8221 IIA or AD8610 JFET AMP, also
low INL ADC.
2. Pay attention to some inductutors in filter network, it"s value changes
will current pass it. It"s better to use amplifier to build active filter.
3. Use higher power supply, use dual power supply, or use rail to rail
amplifer when singl power supply. |
[2005-12-14 11:28:14] |
| [问：polarisdll] |
我是在校学生，项目中要用到仪表放大器，由于经验不够，请问ADI有没有关于运放（包括一般运放和仪表运放）的使用方面的实用的文档或者书籍？？ |
| [答：Mariah] |
Yes, please go to our website to download it. |
[2005-12-14 11:29:17] |
| [问：benyimi] |
10MHZ nv信号放大用AD8139放大器可以做到么? |
| [答：Mariah] |
You have to calculate the total noise for your circuit configuration.
And then decide whether it fit or not. For lowest amplifier, AD8099 has
the lowest noise performance. |
[2005-12-14 11:32:04] |
| [问：yxm_2005] |
我想测量0～100UA的弱电流，使用仪表放大器，前端电路如何使电流变为电压输入至仪表放大器 |
| [答：Eagle] |
Please use differential connection, choose AD8221 (100G Ohm input impedence),
use 10k Ohm percision resisiters between +Vin and -Vin to convert 100uA
to 1V, then set gain =5 or 10 to gain it up. |
[2005-12-14 11:32:18] |
| [问：braingk] |
解决仪表放大器的温度飘移问题,有何妙计?要从几方面入手? |
| [答：Yiming] |
1. 请选用温漂小的电阻。
2. 也可以用校正的方法:需要温度传感器。 |
[2005-12-14 11:32:35] |
| [问：pepjin] |
如何处理仪表放大器应用时所出现的共振问题? |
| [答：Mariah] |
What does "共振" mean. Is it self-oscillation? |
[2005-12-14 11:32:47] |
| [问：zhao
huaxishi] |
你好，我想做毫伏级的测量，要求较高的输入阻抗，您能不能给推荐一款放大器或仪表放大器？ |
| [答：Jing] |
AD8221 is a good solution . it"s input impedence is about xGohm and
the offset voltage is just 2uV(max) |
[2005-12-14 11:32:48] |
| [问：htc703] |
请问有差分输入、差分输出的放大器吗？ |
| [答：Jing] |
yes we have.Please refer to AD8139,AD8133/4,AD8138 etc |
[2005-12-14 11:33:16] |
| [问：dilandi] |
ADI有哪些最新的仪表放大器产品 |
| [答：Yiming] |
AD8220/1/2，AD8250,AD8553等 |
[2005-12-14 11:34:03] |
| [问：zwr7810] |
请问对于采集音频信号，选用什么型号的仪表放大器？ |
| [答：Eagle] |
AD623 is good to remove some noise. |
[2005-12-14 11:34:04] |
| [问：wactd] |
我要设计AD9243的前端差分放大，信号频率1MHz,输入0~5V，单+5V电源供电，G=+1，能否提供一个最优的解决方案 |
| [答：Yiming] |
请用AD8138。 |
[2005-12-14 11:35:25] |
| [问：pengxuelian] |
仪表放大器不适合做交流放大器，对吗？ |
| [答：Mariah] |
It can amplify AC signal. But generally speaking, the bandwidth of IN-AMP
is low. |
[2005-12-14 11:36:48] |
| [问：lijin_as] |
ad8250最大输入范围为多少？能否达到+/- 10V |
| [答：Steve] |
The AD8250 can operate on +/-12V. It can condition +/-10V signals. |
[2005-12-14 11:36:51] |
| [问：qindao] |
青岛哪里可以买到你们的产品 |
| [答：Yiming] |
艾睿电子(ARROW NC)青岛代表处 中国山东省青岛市香港中路12号丰合广场B210室 266071 (0532)
5026916 (0532) 5026646
基通国际贸易（上海）有限公司青岛代表处 山东省青岛市山东路1号滨海花园海丽楼9B 266071 (0532) 5028620 (0532)
5026854
安富利电子行销公司（Avnet）青岛代表处 山东省青岛市福州南路16号中港大厦1120室 266071 (0532) 5773254 (0532)
5710557
世健(Excel Point)系统有限公司青岛代表处 山东省青岛市香港中路12号丰合广场B座503 266071 (0532) 5026539
(0532) 5026537
(0532) 5026543 (0532) 5026543 |
[2005-12-14 11:37:09] |
| [问：wy56] |
我的传感器输出的信号电压是缓慢变化的直流电平信号，无法采用交流耦合的方法，请问还有其它的方法吗？例如设置静态偏置电压？ |
| [答：Eagle] |
Then you had to use DC coupler, if you are use differential input, the
unwanted DC level should be common mode voltage to IIA. It it"s high,
use AD629 or AD628. Use higher power supply (+/-15V)will help it"s in
the range of IIA. After the IIA, the DC common mode DC level should be
removed. |
[2005-12-14 11:37:41] |
| [问：betterpao] |
能否讲解关于增益的问题? |
| [答：Yiming] |
假如放大倍数为A，那么增益为20*lg(A)。 |
[2005-12-14 11:38:25] |
| [问：liduming] |
传感器零点输出可正可负，仪表放大器单电源供电，即使Vref有不同的DC电压，也不能正确放大输出，但先把传感器零位输出调为正，则可，或给仪表放大器正负供电。对吗？谢谢 |
| [答：Mariah] |
The problem you have is the input common mode voltage. Please see figer
22 in page 8 of the AD623 datasheet. If you give the part dual supply,
that will solve the problem. |
[2005-12-14 11:38:46] |
| [问：qindao] |
压力传感器信号的采集应该采用哪个放大器比较合适 |
| [答：Yiming] |
请用AD8555 |
[2005-12-14 11:39:10] |
| [问：T4T4T4] |
如何滤去仪表放大器中高频共模信号?有具体电路吗? |
| [答：Eagle] |
If you use AD8221, it will help to remove it, the CMRR is still very
high at 10KHz. If higher, please add filter. 2 small serial resistor in
each input line and a small capactors between +Vin and -Vin will help
to config a low pass filter. |
[2005-12-14 11:39:31] |
| [问：youyubing] |
请问福建ADI的代理？ |
| [答：Yiming] |
美国模拟器件公司深圳代表处 广东省深圳市深南中路2070号电子科技大厦A座1507-08室 518031 (0755) 83781959
(0755) 83780142
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(0591) 7848456 (0591) 7845280
艾睿电子(ARROW XM)厦门代表处 福建省厦门市厦禾路189号银行中心8层10单元 361003 (0592) 2394567 (0592)
2394000
基通国际贸易（深圳）有限公司福州代表处 福建省福州市五四路158号环球广场1602室 350003 (0591) 7804393 (0591)
87804854
基通国际贸易（深圳）有限公司厦门代表处 福建省厦门市厦禾路820号帝豪大厦2405室 361004 (0592) 2961875 (0592)
2961876
安富利电子行销公司（Avnet）福州代表处 福建省福州市五四北路283号天骅大厦2118室 350003 (0591) 7737851 (0591)
7737194
安富利电子行销公司（Avnet）厦门代表处 福建省厦门市湖滨南路28号皇达大厦12/F,Unit M&L 361004 (0592)
5186090
(0592) 5186091
(0592) 5186092 (0592) 5186093
世健(Excel Point)系统有限公司厦门代表处 福建省厦门市汇腾大厦1606室 361012 (0592) 5042386
(0592) 5114572 (0592) 5042385 |
[2005-12-14 11:41:02] |
| [问：ydknow] |
如果积分器的输入信号幅值一直比较小，而放大器的直流漂移导致积分器发生饱和，请问如何解决这个问题呢？ |
| [答：Eagle] |
Chose a low bias ampfiler such as AD8610. |
[2005-12-14 11:41:07] |
| [问：braingk] |
仪表放大器增益非线性和那些因素有关？增益非线性如何处理? |
| [答：Steve] |
Gain nonlinearity is influenced by the open loop gain of the internal
amplifiers. It is the deviation from the ideal gain. There is not much
you can do to correct for this. |
[2005-12-14 11:42:02] |
| [问：pengxuelian] |
一个单电源+10V的交流差分放大器，5KHz频率，增益40~60dB,用哪款合适 |
| [答：Eagle] |
AD8220 if single power supply, of AD8221 if dual power supply. |
[2005-12-14 11:42:42] |
| [问：waterbird] |
关于运放PSRR的问题，当AD620的供电采用由DC/DC产生的＋－12V时，DC/DC130kHz，理论上AD620的PSRR只有20dB，我对这不甚理解，还请指教 |
| [答：Steve] |
Yes, this is true for low gains. That is why it is important to filter
switched power supplies. |
[2005-12-14 11:43:45] |
| [问：benyimi] |
nv信号放大有什么方案么? |
| [答：Forest] |
这个和你的带宽有关系，你是高带宽还是低带宽？我建议你采用低噪声放大器。 |
[2005-12-14 11:44:00] |
| [问：paynewon] |
请问在处理差动微弱信号的时候应该注意什么？谢谢！ |
| [答：Forest] |
除了要采用低噪声仪表放大器AD8221以外，滤波器的设计也比较关键。 |
[2005-12-14 11:45:07] |
| [问：zhke] |
请问:放大器在防静电上通常采用什么样的措施比较好? |
| [答：Jing] |
you can refer to page 29 for RFI filter and you can also apply guard
ring for AMP input and you can also use ESD protection wrist ring |
[2005-12-14 11:45:12] |
| [问：lijin_as] |
AD8250的单片售价大概为多少？ |
| [答：Yiming] |
还处于预发布状态。 |
[2005-12-14 11:45:44] |
| [问：pepjin] |
如何减少差分输入的信号对仪表放大器的干扰？在设计仪表放大器时信号线和地线的布局分布应如何安排？ |
| [答：Eagle] |
Single point of Analog GND, all GND is star connect to this point. Use
shielding cable for +Vin and -Vin cable, the GND also connect to this
point. Use filter to limite the bandwidth (use 2 serial resistors and
a shut capacitor between +Vin and -Vin to config a simple filter). |
[2005-12-14 11:45:54] |
| [问：wactd] |
放大器使用单电源供电和双电源供电有什么区别吗？比如我使用op113，但电源供电的话，从理论上来讲会不会降低它的精度？ |
| [答：Jing] |
if you use +/- power supply,you can get more headroom and output range.You
can also use big gain to minimize common mode voltage.For OP113, if you
use +/- power supply ,you can get better performance. |
[2005-12-14 11:47:17] |
| [问：myrolite] |
在采集系统中有多个输入时,往往要采用复接器,请问对复接器有和要求? |
| [答：Forest] |
开关的等效阻抗和平滑度会带来一些信号的损失，另外等效电溶也会由于电荷注入效应带来不必要的电荷。你可以选用ADI的ADG12xx和ADG14xx系列。
|
[2005-12-14 11:47:47] |
| [问：qiyu] |
你好，如何选择AD系列放大器的具体使用，比如在共摸电压较大时，功率损耗怎样？ |
| [答：Eagle] |
Use AD629 if high common mode voltage. AD629 has +/-270V common voltage
and 1.2mA Quiescent Current. AD628 is +/-120V common mode voltage. |
[2005-12-14 11:48:04] |
| [问：dragon
668899] |
我试过op495的典型差动放大电路，能否给出一个调零的实用电路？他的最高增益设置为多少最合适？ |
| [答：Mariah] |
Actually, you can find some offset trim circuits in one of ADI"s technical
book. Please call 800-810-1742 to get these circuits. |
[2005-12-14 11:48:16] |
| [问：ypqecum] |
对于相同传感器采用不同的放大器采集的信号有0FFSET问题，如何修正 |
| [答：Yiming] |
可以在输出端数字域中直接减掉。 |
[2005-12-14 11:48:27] |
| [问：zw-wu] |
我要用在电能质量监测方面,不知选项用什么仪表放大器比较好一点 |
| [答：Forest] |
AD8221是低噪声的仪表放大器。 |
[2005-12-14 11:48:52] |
| [问：sfslx] |
在仪表放大器的ＲＥＦ端加入反馈参考点，用于完成低通的滤波，这样会不会影响它的共模抑制比性能？ |
| [答：Forest] |
共模抑制比主要是由于仪表放大器的前端两个运放和电阻决定的。 |
[2005-12-14 11:50:01] |
| [问：Jeff.Liu] |
请问：对于１０ＵＶ左右的差分电压信号，是中间插一级放大后用ＡＤ８２２１好，还是直接用ＡＤ８２２１放大好？！ |
| [答：Jing] |
I think you can use a chopper amplifier before AD8221 should be better
such as AD8230. |
[2005-12-14 11:50:54] |
| [问：pepjin] |
仪表放大器如AD8221对电源有和特别要求?它对电源的波纹要求最低限度要多高? |
| [答：Forest] |
没有特殊要求，AD8221 的PSRR是140dB |
[2005-12-14 11:51:47] |
| [问：xwlcba] |
我要设计一种精密的数据采集设备，输入1mV左右,频段为DC-200kHz的信号，而且还有与此信号幅值差不多相同的共模干扰。设备要求信号放大到1V左右，且在放大过程中、在整个关心的频段内相位匹配。第一级采用三仪表放大器放大20倍，第二、三级采用同相分别放大10、5倍。所有运放均采用OP37,但发现直流偏差较大，尤其是随温度漂移，请问如何解决温漂？ |
| [答：Jing] |
I think you can use a low drift AMP such as AD8555,AD8221/2. |
[2005-12-14 11:51:54] |
| [问：adlion] |
仪表放大器的增益,如何出现非线性,如何进行处理 |
| [答：Eagle] |
Use fix gain IIA such as AD8225 (fixed gain of 5). Choose a percision
resistors as gain resistors of AD8221. If you use switch (such as ADG408)
to change the gain resistors, you need consider the impendence of switch.
Use a new and low on resitor switch such as ADG1408 will be better in
this case. Consider the temperature drift of any component on the PCB,
try to get almost the same temperature for all component. |
[2005-12-14 11:51:57] |
| [问：adlion] |
如何实现两个仪表放大器的同步工作?需要增加什么电路或元件? |
| [答：Forest] |
无法控制仪表放大器，它是模拟电路 |
[2005-12-14 11:52:27] |
| [问：waterbird] |
请问ADI那种仪表放大器适合用在高精度,高输入阻抗,高共模抑制比的生物医学仪表？ |
| [答：Eagle] |
AD8221 is the best choice, even it"s not pin to pin with AD620. The
new pin layout is better to get high performance and easier PCB layout. |
[2005-12-14 11:52:56] |
| [问：hzplq] |
与超低噪声PGIA的A/D采样芯片（如CS5534）相比，ADI的仪表放大器在使用上有什么大的优点。 |
| [答：Forest] |
输入阻抗高，共模抑制比高，噪声低 |
[2005-12-14 11:52:59] |
| [问：hanxin] |
我想了解一下,AD8555/6也是ADI的可编程的仪表运放,在应用上可以单线编程,TI有一款PGA309,可以帮我对比一下优势吗? |
| [答：Forest] |
噪声低，价格便宜。 |
[2005-12-14 11:53:39] |
| [问：qindao] |
用放大器可以做电流源，做小信号电流源（1～2ma）应该用哪个器件比较合适，有参考电路吗？ |
| [答：Jing] |
I think you can use AD8027 to do that.I can"t past the reference circuit
here. You can contact with 800 810 1742 to do that. |
[2005-12-14 11:54:29] |
| [问：braingk] |
仪表放大器具有调零功能吗?它对频率特性有何影响？它又如何和信号通道隔离？ |
| [答：Eagle] |
AD8628 is chop amp which is auto zero. IIA normally does not need adjust
zero because it"s good enough. AD8221BR is 25 μV max input offset voltage,
0.3 μV/°C max input offset drift and 0.4 nA max input bias current. |
[2005-12-14 11:55:17] |
| [问：32kmcu] |
我需要采集电力线上的电流和电压，希望精度是16位，采样速度为250KSPS，功耗尽可能的低，封装尽可能小，供电电压尽可能的简单，EMI/EMC特性尽可能好。请推荐ADI的型号和参考完整方案设计，非常感谢！ |
| [答：Eagle] |
May I suggest use OP4177ARU as amplifier, AD7656BST (6ch Simultaneous
sampling ADC, 160mW at 250 kSPS with 5 V supplies, 85 dB SNR at 50 kHz
input frequency), ADSP-BF531 DSP(low power $5.x DSP)?
Please contact with ADI local office or China Support Center: 800 810
1742.
OP4177: Low Offset Voltage: 60 V Max
Very Low Offset Voltage Drift: 0.7 V/C Max
Low Input Bias Current: 2 nA Max
Low Noise: 8 nV/√Hz
CMRR, PSRR, and AVO > 120 dB Min
Low Supply Current: 400 A/Amp
Dual Supply Operation: +/-2.5 V to +/-15. |
[2005-12-14 11:59:43] |
| [问：chen-lai] |
用于PT1000温度测量的低功耗，低成本的仪表放大器？ |
| [答：Eagle] |
AD8220 or AD623 is good choice, you can also consider AD7793 24bit Sigma-Delta
ADC with on chip IIA and reference). |
[2005-12-14 12:01:56] |
| [问：braingk] |
请问谁使用过AD620仪表放大器，有那些要注意的地方，还需要电容做旁路和滤波吗？除了datasheet，那里还有别的参考资料可以看？ |
| [答：Eagle] |
AD620 is released 15years ago, many application document on magazine.
AD8221 is better and chipper. Please download datasheet on www.analog.com.
Very simple filter will be needed if common mode signal is very high.
No filter needed if less than 10kHz common interference. |
[2005-12-14 12:04:52] |
| 非在线问答： |
| [问：] |
1、关于最新的3G的测试解决方案
2、另一个老问题：用频谱分析仪测试CDMA信号时，测量出的读数是否与RBW设置有关；读数要不要加修正值；如何正确读数呢？ |
| [答：] |
1.about the 3G, please go to agilent's website to get more
information. 2. setting of the RBW does affect the output, in the instrument
there is a mode to caculate the CDMA signal power, you simply enable that
mode and read the outputs. |
| [问：] |
10M的单电源运放,兼顾大批量订货价格,贵公司有什么好推荐? |
| [答：] |
there are many other parameters can affact your choice of
AMP, like supply Voltage, accuracy and noise, etc. please go to the following
website to find the most suitable AMP for you.http://www.analog.com/dynamic/parametric
/scResultsDisplay.asp?SearchType=PSS&ProductLine=OPA |
| [问：] |
24bit AD simpling system该采用哪个器件 |
| [答：] |
it depends on what's the performance (speed, noise, drift
etc.) you need,ADI offers many 24 bits ADC, you can get detailed information
from http://www.analog.com/dynamic/parametric/scResultsDisplay.asp?SearchType=PSS&ProductLine=ADC |
| [问：] |
ad1852应该如何应用好些？我以前用过，但没有调出结果来，问过AD公司好多技术支持，也没能解决问题，后来就干脆不用了，现在回想还有些遗憾。 |
| [答：] |
before you use a chip, please read its datasheet carefully
and strictly follow the instruction circuit. |
| [问：] |
ad7714的转换时间最快是多少? |
| [答：] |
the fastest throughput of AD7714 is 1k Hz, when the master
clock is 2.4576M |
| [问：] |
AD8221的售价是多少？ |
| [答：] |
不同的封装，千片数量的单价为1.99，2.32美元军品为4.06美元。具体价格请与本地代理商联系。 |
| [问：] |
AD8250是否适合做 16位ADC的驱动？ |
| [答：] |
Before you make the decision, you should be very clear about
the system error requirement. The condition of "16 bits resolution"
of the ADC can not determine whether AD8250 is OK. Considering the noise
and gain nonlinearity, AD8250 would be a choise for 16 bits ADC driver. |
| [问：] |
ad8604能否用于比较器 |
| [答：] |
Amplifier could be used as the comparator, but several points
should be taken into account. For details, please go to the link: http://www.analog.com/library/analogDialogue
/archives/37-04/comparator.html |
| [问：] |
ADI的可为DDR2内存供电的电源管理芯片有哪些？用于汽车电子中ADI都有些什么产品呢？谢谢专家！ |
| [答：] |
for power supply chips, please go to the link below to detailed
information.http://www.analog.com/en/subCat
/0,2879,766%255F820%255F0%255F%255F0%255F,00.html. ADI also offers many
kinds of chips can be applied in Automotive applications like converters
amplifiers, MEMS, MCU, DSP, etc. |
| [问：] |
ad有没有两路同步的12位模数转化芯片 |
| [答：] |
yes，We have like AD7862,AD7864,AD7866 and etc. For more
information please refer to http://www.analog.com/dynamic/parametric
/scResultsDisplay.asp?SearchType=PSS&ProductLine=ADC |
| [问：] |
ai采集0-5v ,0-20ma信号,请推荐一种隔离设计方案 |
| [答：] |
for the isolate chips information, please go to http://www.analog.com/en/subCat/0,2879,759%
255F783%255F0%255F%255F0%255F,00.html |
| [问：] |
as far as I know, the on chip resistor can not accurately implemented,
but we can carefully choose off-chip resistors value, how ADI can guarantee
their off-chip resistor is accurate? |
| [答：] |
first, I am fraid that what you have known is wrong. The
on-chip resistors are easy to be trimed, thus they can be matched quite
well. Second, ADI does not provide any resistors, you have to buy it by
yourself and test the real value of the them before you use them. |
| [问：] |
nA 级甚至0.几nA的光电信号放大采用什么样的运入及如何设计放大电路 |
| [答：] |
you can use AD795, about the circuit, please refer to AD795's
datasheet Figure 42, you can also have a look at AD8603/07/09;AD8541/42/44. |
| [问：] |
op495 1k的量,多少钱一片 |
| [答：] |
1k的量的话，4.07美元一片,具体报价请与当地代理商联系。 |
| [问：] |
出现了电磁干扰，怎么办？ |
| [答：] |
要想完全抑制电磁辐射是不可能的，但通过对电路进行合理设计，或者采取部分屏蔽措施，可以大大减轻电磁干扰的辐射。 例如尽量缩短电路引线的长度和减小电流回路的面积，是减小电磁辐射的有效方法；正确使用储能滤波电容，把储能滤波电容尽量近地安装在有源器件电源引线的两端，防止各电路中的有源器件(放大器)通过电源线和地线产生串扰；把电源引线的地和信号源的地严格分开，或对信号引线采取双线并行对中交叉的方法，让干扰信号互相抵消，也是一种减小电磁辐射的有效方法；利用散热片也可以对电磁干扰进行局部屏蔽，对信号引线还可以采取双地线并行屏蔽的方法，让信号线夹在两条平行地线的中间，这相当于双回路，干扰信号也会互相抵消。 |
| [问：] |
对于10KHz的方波小信号（3mVpp),要求放大到4Vpp，什么型号的运放和什么形式的电路较为合适？（单电源，不考虑功耗问题）谢谢！ |
| [答：] |
For this kind of application, you can consider AD8099 which
is a very low noise part. |
| [问：] |
对于瞬态尖峰宽范围的信号处理，使用什么芯片最好 |
| [答：] |
What kind of processing you want to do? you may have a look
at our Log amplifers. |
| [问：] |
放大器选的什么芯片？谢谢 |
| [答：] |
请问您设计的是什么电路，对于不同要求，使用芯片也不同，你可以去得到详细信息http://www.analog.com/dynamic/parametric
/scResultsDisplay.asp?SearchType=PSS&ProductLine=OPA |
| [问：] |
轨到轨是什么意思,相对于不是轨到轨的器件它有什么优点?谢谢! |
| [答：] |
轨到轨是指器件的输入，输出范围和电源供电范围非常接近（100-200mv），这样同样供电情况，轨到轨的动态范围会更大 |
| [问：] |
贵公司的此类产品，和业界的其他公司相比较，有什么独特的地方？谢谢 |
| [答：] |
excellent performance, reasonable price |
| [问：] |
具体用什么方法实现直流回路？谢谢 |
| [答：] |
What do you mean DC loop? Amplifier of course can do DC
amplification. |
| [问：] |
模拟差分怎样实现? |
| [答：] |
you can use a transformer or use a different amplifer to
achieve it |
| [问：] |
能不能 给出 这些常用放大芯片的具体资料，给我发过来啊？我对你们公司将要发布的新芯片很感兴趣guguwe@163.com
谢谢了：） |
| [答：] |
您可以去http://www.analog.com/en/cat/0,2878,759,00.html 查询下载您需要的放大器的资料 |
| [问：] |
能否推荐一个ADI的前端差分放大加后端ADC的芯片组合！
要求：放大的输入信号：0---+/-30mV,放大输出差分信号，0--2.5V
ADC要求24位，低速测量！ |
| [答：] |
you can try the sigma-delta ADCs, like AD7794, this is 24bits
ADC with on-chip in-AMP |
| [问：] |
能否推荐一个适合轨对轨输出的运算集成放大器？ |
| [答：] |
There are many amplifiers which have rail to rail outputs.
Please raise your requirement in detail. |
| [问：] |
你好，应用公司的器件来做数据采集，实现mv级的测量，请推荐一个解决方案 |
| [答：] |
这取决于您的信号频率，需求精度，如果有具体问题，欢迎发邮件到China.support@analog.com询问 |
| [问：] |
您给的计算公式好像无法计算出http://www.analog.com/Analog_Root/static/techSupport
/designTools/interactiveTools/inamp/inamp.html?inamp=AD623%205V，我是根据这个程序来判断的？ |
| [答：] |
网页给出的各点电压，就是通过公式计算出来的 |
| [问：] |
请介绍高压摆率的程控放大器 |
| [答：] |
how fast the Slew rate do you need? You can get detailed
information from http://www.analog.com/dynamic/parametric
/scResultsDisplay.asp?SearchType=PSS&ProductLine=OPA |
| [问：] |
请问ADI公司的产品与其它公司的产品相比有哪些优点? |
| [答：] |
ADI是高性能模拟器件/数字信号处理器供应商。 |
| [问：] |
请问何时能看到AD8250的资料 网上似乎没有 |
| [答：] |
还没有正式发布 |
| [问：] |
请问如何搭建一个性能非常稳定的DualSloop的AD转换器？谢谢！ |
| [答：] |
选用ADI高性价比运放，开关，MCU，加高效的软件。 |
| [问：] |
请问在太原哪里可以买到ADI的产品？ |
| [答：] |
对不起，ADI在太原没有办事处，太原客户请通过下面的链接:http://www.analog.com/intl/china/salesdir/distributors.html联系。 |
| [问：] |
如果能找到IC,请与我联系:13113917475 |
| [答：] |
请问你需要什么IC，请发信到china.support@analog.com咨询. |
| [问：] |
如何把ＮＶ信号放大？ |
| [答：] |
请问幅值有多大？频率为多少？带宽为多宽？ |
| [问：] |
如何降低手機發射時干擾的問題,請簡要說明如何選用適合的ADI的IC及PCB電路設計的一般要領. |
| [答：] |
详见ADI仪表放大器应用指南5-8节 |
| [问：] |
声信号拾取电路有什么组成？ |
| [答：] |
传感器，放大器，滤波器 |
| [问：] |
师傅:你好我有个希望你能帮个忙,
我想找一种集成电路,因为原来的型号看不清,之所以向尊敬的IC供应商求助,这种IC是16脚双直插,1脚是接负极,16脚是接正极,电压5V,2\3\4脚是串口输入,5--12是供数码管共阳,需要量是第一批1000片.急!我已经分析过了,这种集成电路是8路多通道转换开关类,希望IC供应商给我报价. |
| [答：] |
仪表放大器可以提供对微弱信号的放大同时抑制共模信号。 |
| [问：] |
微小的信号如何放大 |
| [答：] |
对于8:1多路复用器可以考虑ADG708/ADG758/ADG728/ADG738. |
| [问：] |
为什么自己搭建的仪表放大器的CMRR不如片上集成的仪表放大器的好？ |
| [答：] |
这是因为芯片内部的薄膜电阻可以达到精密匹配，而用运放和外部电阻搭建很难达到这样的精度。 |
| [问：] |
我的理解，仪表放大器就是可以精确放大微小输入信号差的opamp，对吗？ |
| [答：] |
可以这样理解，但是仪表放大器往往是由两个或者三个运算放大器组成的。 |
| [问：] |
我是学通信的，请问在ad公司作研发需要哪些微电子方面的专业知识。 |
| [答：] |
我们每年会有学校招聘。具体要求我们人力资源的同时会提出。如果需要，你可以与我们北京设计中心联系010-8278
2727 |
| [问：] |
我有一个无线遥控装置,有效距离太小(<500m),能否加一运放加大功率,以增加通讯距离 |
| [答：] |
您可以通过增大输出功率来增大传输距离，也可以通过改善天线来增大传输距离。您的无线遥控装置的射频频率为多少？现在的发射功率为多大？使用什么样的天线？ |
| [问：] |
希望了解有关宽频带放大器，100M左右 |
| [答：] |
我们有很多这样的器件。有电压反馈型的也有电流反馈型的。比如说AD8099, AD8009等。具体的选择您可以把频宽、增益、供电电压、输入信号特性等告知我们。联系方法china.support@analog.com. |
| [问：] |
想对常见放大器仪表问题加深 了解 ，并处理好他的维修 |
| [答：] |
请参考http://www.analog.com/en/DCcList/0,3090,759%255F%255F62,00.html.或者与china.support@analog.com联系。 |
| [问：] |
想尽快得到AD7792的中文应用报告,报价及样片,最好能提供5片.郑州办事处的同志讲购买最少100片.我们在开发阶段希望得到支持. |
| [答：] |
对不起，我们现在没有中文的资料。如果再应用中遇到问题，请与800 810 1742或者china.support@analog.com联系。对于样片，请直接到我们的网址申请，我们可以免费提供。 |
| [问：] |
要设计一个肌电测试仪，能给推荐一款ADC吗？谢谢。 |
| [答：] |
我们有很多产品可供选择。AD7685可以推荐给您。对于这个ADC，您可以选择16位的产品。我们这个系列产品名为PulSAR.详细情况请联系china.support@analog.com. |
| [问：] |
仪表放大器能否消除P频率在0到1000Hz时的f/2干扰 |
| [答：] |
我们需要知道您的详细噪声情况。具体请与china.support@analog.com联系。 |
| [问：] |
仪表运放的REF脚能接Vcc/2. |
| [答：] |
是。但这主要与您的供电电路、输入信号范围、输出信号范围有关系。详细请联系800 810 1742. |
| [问：] |
仪表运放与其他运放有何区别？ |
| [答：] |
请参考AD8221的datasheet或者是在线研讨会的第6页。还有问题请联系china.support@analog.com. |
| [问：] |
用opamp搭建仪表放大器，为什么不如片上仪表放大器的CMRR好？ |
| [答：] |
请参考AD620的datasheet或者是在线研讨会的第5/6/7页。还有问题请联系china.support@analog.com. |
| [问：] |
用普通运放组差分输入-差分输出交流放大器，信号频率5KHz, 单+10V供电，用哪个信号合适， |
| [答：] |
Do you mean what amplifier are good for your requirement?
For youre requirement, several amplifier can do what you want. For example,
OP1177. But we have integrated differential amplifier, for example, AD8138/9.
These two parts have very low noise for precision application. |
| [问：] |
有没有使用同相放大而不引入噪声的可能？ |
| [答：] |
There is no possibility to do that, because all the amplifier
has noise. |
| [问：] |
有没有适合大批量生产工业级压力变送器、低价位的芯片 |
| [答：] |
It depends on your application and system requirement. Please
provide your application in details, then we can recommend our parts. |
| [问：] |
有些时候测量CDMA与GSM载波功率时，频谱分析仪的读数还要加个修正值是何意思？为何要加修正值呢？ |
| [答：] |
I think you may ask the support from the manufacture of
the spectrum analyser. |
| [问：] |
在称重系统中用哪一款仪表放大器好？ |
| [答：] |
For weigh scale system, you can consider AD8230 which is
a very precision instrumentation amplifier. |
| [问：] |
在分离电源电路设计中,放大器和三极管如何运用? |
| [答：] |
Amplifier could be used as in control and feedback loop.
|
| [问：] |
在看ADI的参数表时,不明白n/a表示什么?谢谢! |
| [答：] |
It means "not available". |
| [问：] |
在使用仪放的时候是否要考虑输入端的阻抗匹配？ |
| [答：] |
The input impedance of the instrumentation amplifier is
very high. There is no need to consider impedance matching. |
| [问：] |
针对双电源的应用有哪些特点？ |
| [答：] |
For dual supply system, generally, they are used in industrial
applications, since they need to handle large and bipolar signals. Large
signal range also improves the anti-noise and anti-interference performance
of the system. |
| [问：] |
做比例放大时，如果放大五倍，前端电阻和反馈电阻选100欧、500欧好还是1K和5K的好，选择的依据是什么呢 |
| [答：] |
It depends on what you really care about in your system
design. If the noise performance is the concern, then small resistor is
better. If power consumption is the concern, large resistor should be
considered. |
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