如何为您的ADC选择最合适的基准电压源和放大器?

如何评定一颗ADC非线性？丢码？
[答：Jing]
you can use ADC"s INL and DNL parameter to evaluate the non-linearity and you can also use ENOB parameter to check code loss. Thanks!Generally ENOB releated with ADC"s SNR
[2006-2-28 10:32:08]
[问：吉星]
在差分输入时，不考虑直流，使用差分放大器和变压器哪个更好．
[答：Mariah]
Transformer is better for the better noise and distortion performance, especially in very high frequencies.
[2006-2-28 10:32:14]
[问：Jane Yang]
请问应如何处理板级噪声对于高精度AD的影响？特别是输入部分的噪声？
[答：Jing]
This is a good question and it"s very difficult to answer. Generally, You should consider all the input noise derived from sensor/AMP/BUFFER. You can also use a LPF to reduce the input noise. Remember the BGP of AMP should be 100x of ADC"s throughput. Thanks!
[2006-2-28 10:34:30]
[问：石林艳]
AD变换的参考基准源很重要，对模拟供电电源和数字供电电源的要求也很高吗
[答：Rui]
模拟供电电源，和数字供电电源相对基准源来说，精度要求相对较低，一般情况下用10uF的电容和0.1uF滤波即可。
[2006-2-28 10:34:31]
[问：zcs_1]
请解释一下，分辨率和转换精度之间的区别
[答：Mariah]
For conversion accuracy, it involves many aspecs. For example, INL, DNL, offset, gain error.
[2006-2-28 10:34:46]
[问：Leemour]
对不起能否讲一下什么是：RAIL TO　RAIL，这个我一直不太明白。
[答：Xiangquan]
轨到轨指输入轨到轨，或输出轨到轨，具体指的是输入信号或者输出信号的范围基本接近于电源，譬如电源是+-5V，输入信号或输出信号可以达到+-4.9几V以上
[2006-2-28 10:35:25]
[问：jlwg]
很多种adi的a/d转换器件都自带有标准电压源，请问是使用器件自带的标准电压源好还是另外使用独立的标准电压源更精确？
另外使用ad7710时，每次转换信道后的第一次转换结果是否是有效的？
[答：Troy]
Use an independant reference to get the highest accuracy and lowest temperature drift.  It depends on how much accuracy your application needs over temperature.
[2006-2-28 10:37:14]
[问：xwlcba]
您提到驱动AD的运放增益带宽积要求大于100倍采样速率,请问对运放的转换速率有何具体要求?
[答：Troy]
To get the lowest distortion (THD), we recommend using an amplifier with at least 100x gain-bandwidth product greater than the sample rate.
[2006-2-28 10:39:36]
[问：bly1979m]
本人最近做了一个项目用于精确测量温度的，就用到了这两种器件！请推荐几款贵司产品？并说说它的大概价格是多少？
[答：Jing]
It"s depend on the accuracy of your system requirement. I am pleased to recommend that you can use our ADR421+AD7799. For price, you can check it on our web or consult our distributor according to your volume. Thanks!
[2006-2-28 10:39:40]
[问：guahuahua]
选用AD7788时，能选择的最适当的参考基准源是哪一款
[答：Mariah]
You can try the software we recommended in the presentation "reference selection wizard". You can download it from the link of http://www.analog.com/Analog_Root/static/techSupport
/designTools/voltageReference/download.html

 
[2006-2-28 10:41:33]
[问：arzhiy]
RC滤波器设计在ADC前就会出现相位漂移的情况，这样采集到的信号是一个失真的，是这样的吗？
[答：Troy]
The RC filter will not add any distortion to the signal.  The RC filter will reduce noise at frequencies higher than its cutoff frequency.  This improves ADC performance because it reduces out-of-band noise to the ADC input.
[2006-2-28 10:44:33]
[问：yz_yjg]
我们的有一个双信道数字示波器产品，当进行垂直移位时，即施加给AD9288的直流电平改变时，发现发现基中一个信道在LCD屏上的某些区域的基线变粗（这有规律，如每间隔16或32出现），有2mm到8mm左右不等，更换AD9288即可。大多数是其中的一个ADC有问题，我们希望基线在屏幕上移动时（不加信号），扫描基线的不要发生粗细变化，请问是什幺原因？AD9288能完全消除这种现象吗？
[答：Mariah]
We need to know more details about your circuit. Would you please send your question and schematic in details to china.support@analog.com, and then our engineer will help you on that.
[2006-2-28 10:45:35]
[问：callhxw]
双极性输入信号，采用OP转换为单极性的到ADC，设计时应关注哪些？
[答：Jing]
First , you can select AD8129/AD8130 to realise the function. But this will reduce the ENOB. I suggest you use differential input ADC too. You should consider the noise from the AMP and the GBP of the AMP.You had better to select a high GBP and CMRR and low noise AMP. Thanks!
[2006-2-28 10:45:35]
[问：Jane Yang]
which reference is better: external or on-chip, for high speed (40~105M) and 12~14bit ADC?
[答：Troy]
External references give better initial accuracy and lower drift over temperature.  Using the on-board reference or an external one depends on the accuracy you need in the application.  Generally speaking, the higher the ADC resolution (# of bits), the more likely you will need an external reference.
[2006-2-28 10:46:16]
[问：liu.gy]
1、就ADI的产品而言，请给出“基准电压源+ADC”的两种方案：分离与集成 两个方案的优缺点？
2、运放到ADC之间什幺时候需要加滤波处理？如果加滤波处理，请给出滤波的方式及性能比较？
 
[答：Xiangquan]
1。集成主要带来方便，但是往往由于工艺的限制往往不能发挥转换器的最高性能，如果选择合适的外部参考源，则可以比较好的发挥转换器的性能
2。运放与AD之间的滤波主要为的是滤除噪声，抗混迭，以及给ADC的转换产生的瞬态能量提供缓冲，一般一阶RC低通滤波即可，或者对于带通滤波，可以根据自己的要求进行设计
[2006-2-28 10:46:34]
[问：chenhaifeng]
放大器的PSRR是否与外电路及输入信号无关？
[答：Haoran]
PSRR主要是电源对信号的影响，与外电路和信号无关
[2006-2-28 10:47:12]
[问：hzluoping]
请问：1）精密ADC的数字地和模拟地的正确接法及对ADC转换精度的影响？
      2）在单片机系统应用时，对精密ADC的启动和数字信号的输出的控制
         有何要求？
[答：Jing]
1> you should consider the system current. If the digital current is small, you can seperate digital GND and analog GND and combine them together in one point. If the digital current or noise is very large, you can also look ADC digital GND as analog GND.
2>I don"t know what you mean. Generally ,some of our ADC has hardware start and software start selection.
[2006-2-28 10:48:39]
[问：arzhiy]
常用的RC往往本生噪声也很大，这样且不是更加增加了采样的噪声？
[答：Haoran]
噪声主要来源于电阻，实际上在可能的情况下或电路稳定的前提下，尽量增大电容可以提高噪声性能。
[2006-2-28 10:48:50]
[问：boclandc]
我采用了AD7671,测试8信道的线性电子尺(等效线性电阻),请问有什幺好的多信道切换,我采用了二片MAX4052后面通过AD620做驱动,但是切换至稳定时间需达10uS,在切换速度上非常不理想.不知贵公司有否这样的方案,使切换速度小于或等于2uS?谢谢!!
[答：Mariah]
ADI has many new mux and switches which has better performance, like ADG121x, ADG13xx and ADG14xx. Also the settling time also depends on your circuit. You can send your schematic and question to china.support@analog.com. Our engineer can analyze your circuit and give out the solution.
[2006-2-28 10:49:42]
[问：ecnanjing_EBY7E]
请问,电压基准的精度和温度系数对AD的精度的影响的换算关系是怎样的?
[答：Haoran]
你可以在今天的资料中找到，并且可以从我们的网站上下载
[2006-2-28 10:50:00]
[问：hzluoping]
模拟地和数字地的接法对ADC影响大，如何作好接地？
[答：Rui]
地的接法一般有两种，1。把地平面分割为模拟地和数字地，或者一层数字地，一层模拟地，然后共同接到共地点。2。不分割模拟和数字地，使用多点接地。
对于第一种情况，注意数字地层和模拟地层不能重迭。
对于第二种情况，要提供尽量多的接地点。
[2006-2-28 10:50:14]
[问：amatist]
基准源有齐纳二极管和带隙电压基准等几种,它们有何优缺点?
[答：Troy]
References built using bandgaps have lower temperature drift, but they are more complicated and more expensive.  Zener references are usually less expensive, but have more noise and may have lower initial accuracy and higher drift over temperature.
[2006-2-28 10:50:22]
[问：amatist]
对电压基准源的要求主要有那些指标?如何选择电压基准源?
[答：Jing]
Intinal accuracy, temperature drift is two of the key factor. You can according to your system error requirement and download our REF+CONVERTER wizard to select the corresponding REF. Thanks!
[2006-2-28 10:50:22]
[问：elmer]
放大信号中出现大的脉冲信号，怎样去除这个信号？
[答：Haoran]
你可以先在运放前增加低通滤波器。
[2006-2-28 10:51:00]
[问：wzj0713]
pA~mA的高动态低变化速率输入的信号调理拟使用ADI产品ad8304，现在需咨询的是如何最小限度的减小引入噪声（从PCB版图、工艺和电路处理两方面）。
[答：Jing]
You can use AD8304 to interface a PIN and converter current to voltage. To minize the input noise, you should select a better PIN--this is the first noise source. Then you should select high accuract resistor and capacitor . Of course, multi layer PCB is better to minize the inout noise.