| [问：nnyy0011] |
目前ADI公司的超过12位上百兆精度ADC产品与以前ADC产品在设计技术和工艺技术上有什么方面的突破或者提高？如何解决运放有限增益、电容匹配度和ADC分辨精度之间的矛盾呢？ |
| [答：Eagle] |
We has some new technology and some specially designed RF gain block, IF differential ampifier (ADC driver such as AD8352). It"s much fast enough. |
[2006-10-18 12:06:10] |
| [问：powertoy] |
稳定性和匹配网络的关系？ |
| [答：Yiming] |
Recommend you to read the RF Circuit Design Theory and Applications (射频电路设计理论及应用) chapter 9: RF Transistor Amplifier Designs. 科学出版社 （Reinhold Ludwig, Pavel Bretchko） |
[2006-10-18 12:07:32] |
| 非在线问答： |
| [问：] |
1、我使用LM324，输入有正反向稳压二极管（8.2V,VCC+=12V,VCC-=-12V),输出有7.5V稳压管，但为啥一直烧（在正常使用中）？
2、信号源负端和电源地何处相连较好（电源器件出处、运放附近）？ |
| [答：] |
Maybe you gain is very hign, LM324 has 1.5mV offset, it's been gained up to 7.5V if gain of 5000, then it shut protect diode. Suggest ty OP4177 which has only 75uV offset. Another possible issue is the DC offset from sensor or front gain stage, then you need AC coupler between gain stages. |
|
| [问：] |
AD7730是5V供电的。如果称重传感器5V供电的话，输出信号太小，不利于抗干扰。如果加入分压电路，容易产生漂移，增加成本。能否将器件的供电电压提到10V以上？ |
| [答：] |
If you cannect the +Vref to the +5V power of the bridge joint piont by a seperated line, -Vref to the GND point of the bridge joint point, then it's easy to remove the interference. |
|
| [问：] |
ADI的运放输入是否可以直接承受较高的ESD，可否提供具体型号 |
| [答：] |
Most Amp is under ESD level of 200V only, you need add ESD protection. Some ADC such as OP2177 has input protection which will protect input to be no more than power rail. Some interface IC such as ADM202E, ADM3202, ADM483E has 15kV ESD protection. |
|
| [问：] |
AD公司目前有多路的运放芯片吗？如8路16路或更多。 |
| [答：] |
Normally 4 amp such as OP4177, AD8674, AD8668. But some very special driver has 8ch, such as ADD8708 (18ch Gama buffer), ADD8701 (12ch Gama buffer) |
|
| [问：] |
ad公司有大功率低噪声的运放吗? |
| [答：] |
Low noise amplifier is typically small signal, such as OP27, AD8672, SSM2109. But some amplifier can drive 150mA current, such as AD8592. |
|
| [问：] |
A类,AB类放大器和D类放大器的稳定性有什么不同?在设计上如何考虑? |
| [答：] |
Class A and Class AB type amplifer are in the same stable level provide the same bandwidth and gain. But class D is quite different. Class D type amplifier need carefully consider L and C effect in feedback network. |
|
| [问：] |
Dear sir!
How to compensate the offset voltage and its drift over large tempereature range(eg. -40~80 Celsius Degree)of an operational amplifer? Give me detailed schematics please |
| [答：] |
A simple way is using a Chop amplifier such as AD8551, AD8628 which has 0 offset and no drift, because it use chop method to remove offset. Another way is choosing a low drift amplifier such as OP2177 which has 60uV Voffset and 0.7uV/'C temperature drift. The third way is using one digital potention meter such as AD5245 to adjust the offset, or use a DAC such as AD5628 to provide another offset to compensate. It need look up table in MCU or DSP. |
|
| [问：] |
how can i know my amplifier reliable or not? |
| [答：] |
I think you mean if it's stable under any condition. Test it under big step signal, observe if any the rings. Test with different frequency sin wave, use sweep is better. You can use a DDS (such as AD9833, AD9954) to generated sweep sin wave. |
|
| [问：] |
ICL7652斩波自稳零运放的失调电流、失调电压温漂和时漂都很低。请问ADI有哪种型号的运放跟ICL7652指标相当或更好？ |
| [答：] |
OP1177 is closest if high power (+/-15V). OP1177/2177/4177 has 60uV offset and 0.7uV/'c drift. AD8571, AD8551, AD8628 is OK if low power supply (5V only). |
|
| [问：] |
如何提高ADC的精度？14位ADC最高有效精度由什么决定？谢谢 |
| [答：] |
You can choice a good ADC with low INL and DNL. Good layout and decouple always helpful. You can also use over sampling. |
|
| [问：] |
采样微弱信号，比如1mv的交流电压，为了防止噪声，是不是接成差分模式最好？能推荐一款正负3.3v供电的相应运放吗？谢谢 |
| [答：] |
Yes. You can use a instrumental amplifier. Here you can use AD623. |
|
| [问：] |
低噪声放大器噪声电压如何计算，计算重点在哪 |
| [答：] |
You need use Vn * Sqrt (BW) + In * Rin + VN of 0~10Hz + VN of input noise. Where Vn is nV/Sqrt(HZ). In is nA/Sqrt(Hz). |
|
| [问：] |
对于小信号的放大，如何选择放大器参数？ |
| [答：] |
For small signal, need low offset amplifer. OP2177 is good choice for both low offset and low drift. You also need low noise. |
|
| [问：] |
烦劳推荐一款低噪声、低压供电（3.3V）的运放。 |
| [答：] |
AD8656. Low noise: 2.7 nV/√Hz @ f = 10 kHz ; Low offset voltage: 250 μV max over VCMOffset voltage drift: 0.4 μV/°C typ and 2.3 μV/°C max Bandwidth: 28 MHz Rail-to-rail input/output Unity gain stable; 2.7 V to 5.5 V operation; −40°C to +125°C operation |
|
| [问：] |
放大器的稳定性补偿是需要考虑到负载的大小,即空载,重负载和轻负载的补偿有何不同? |
| [答：] |
Actually need consider the load type, especially capacitor type. Please make sure 40 degree phase margin. |
|
| [问：] |
放大器振荡产生的主要原因有那些?和EMI有关吗? |
| [答：] |
Most likely because phase margin not enough. Normally we see dirve capacitor load directly with high speed amplifier (such as AD8061, AD8091, ADA4851, AD8006, AD8009), here need add small serial resistors before driver capacitor load. Some times because some Amplifer it self is not unit gain stable device, you need use min gain of 5 or 10 as datasheet required. And, for current feed back amplifiers (such as AD8073), you need use the recommend feed back resistors as datasheet suggest. |
|
| [问：] |
感性负载和容性负载的稳定性补偿方法是否一样?演示中所列三中方法是否也适合于感性负载? |
| [答：] |
L type load need different compensation ways. Actually its change the phase margin. |
|
| [问：] |
高共模电压运放与非高共模电压运放的构造上有什么不同?高共模电压运放的输入级有精密分压电阻,可以这么理解吗? |
| [答：] |
Some high voltage device achieve high common mode level by techonology itself, such as Biplor process (OP2177), or D MOS tech. Or use iCOMS tech to get +/-8V over CMOS type IC (such as AD8662). But some device use internal divided down resistors (such as AD629, it can work on +/-250V common mode voltage) |
|
| [问：] |
工业用仪表放大器一般有哪些特点？ |
| [答：] |
Industry amplifier based on 3 amplifiers, it has high CMRR, high input impedance, and good match so low drift. |
|
| [问：] |
工作于1MHZ宽带VGA型号？ |
| [答：] |
AD603, AD8337 VGA is much fast (90MHz or 280MHz BW). |
|
| [问：] |
共模反馈稳定性如何分析？ |
| [答：] |
Dropped |
|
| [问：] |
环路内补偿方法中加入Rx会增大直流误差，而且减小输出的摆幅范围。对电路的总体性能影响大不大？怎样改善？ |
| [答：] |
It depends on the accuracy you want to get in your system. If you cares about the accuracy and rail to rail output performance, you can use snubber network compensation method which will not influence the DC accuracy. |
|
| [问：] |
精密 AD 的PCB布线有何讲究? |
| [答：] |
The power supply decoupling and ground layout is very critical for precision circuit. |
|
| [问：] |
脉冲前沿1us，持续时间100US，请谈谈设计中应注意的问题，推荐几款A/D芯片。 |
| [答：] |
For high speed converter, ADI provides lots of product with different resolutions. Can you tell the resolution you need and what information you want to get through ADC? Do you only need the amplitude of the signal? |
|
| [问：] |
目前ADI公司的超过12位上百兆精度ADC产品与以前ADC产品在设计技术和工艺技术上有什么方面的突破或者提高？如何解决运放有限增益、电容匹配度和ADC分辨精度之间的矛盾呢？ |
| [答：] |
For the new parts, ADI use advanced technology and process. It can achieve better SNR, SFDR and also lower power consumption. For you second question, can you explain it in much more detail? |
|
| [问：] |
那一款经济实惠的ADI运算放大器可以处理视频信号。 |
| [答：] |
AD8091 ,AD8061, ADA4850/1, ADA4860 |
|
| [问：] |
能不能简单介绍一下放大器的内部结构 |
| [答：] |
If you want to know more about it, you can call 800-810-1742 to get some technical material on the amplifier structure. |
|
| [问：] |
能否将运放和ADC的协同工作作为一个专题研讨会的形式来讲解？？？？ |
| [答：] |
That is a good idea. We will consider it. |
|
| [问：] |
能否讲一下TIA放大器，和应用分析 |
| [答：] |
We have some technical mateiral on ITA application. You can call 800-800-1742 or send email to china.support@analog.com to get the related material. |
|
| [问：] |
你好!
我用LM358设计了一个PWM滤波数模转换电路,为什么一开始上电,硬件就有最高电压输出(此时软件还没有工作).是我设计的问题?还是别的?
请问有没有什么好的办法解决此问题.谢谢. |
| [答：] |
Dropped |
|
| [问：] |
你好！在高精度的测量中，使用线性电源要优于开关电源。那么，如果使用开关电源并在它后面加了线性稳压再给测试电路供电，这样效果和直接使用线性电源会一样吗？ |
| [答：] |
That will be good if you use LDO after the switching power supply. |
|
| [问：] |
你好，请问在ADG509前端使用了RFI滤波器，那么它的输出端，也就是输入到AD620的时候，还要再加RFI滤波器吗？ |
| [答：] |
What is your application? Can you describe your application and circuit design in detail? You can send email to china.support@analog.com. Our engineer will give you suggestions based on your application. |
|
| [问：] |
您说的增益大会使稳定性提高，实际上应该是指增益带宽积大，是么？ |
| [答：] |
No. The gain refers to the noise gain or the noninverting input gain. |
|
| [问：] |
判断运算放大器的稳定方法有那些? |
| [答：] |
Just like what the presentation showed, you can use step input and see the overshooting of the output to tell the stability. |
|
| [问：] |
请讲解一下放大器的寄生参数对放大器稳定性的影响.谢谢! |
| [答：] |
Basically, the parasitic comes from the external circuit and layout. It will influence the stability and signal integration performance. |
|
| [问：] |
请教贵公司现在DA的最高精度是多少位啊? |
| [答：] |
24bits |
|
| [问：] |
请介绍放大器板的防雷措施。谢谢 |
| [答：] |
Dropped |
|
| [问：] |
请介绍几款贵部的应用比较广泛差分放大器(差分输入 差分输出) |
| [答：] |
AD813x, AD815x |
|
| [问：] |
请问，高增益电流型放大器设计要注意什么问题？ |
| [答：] |
电流反馈放大器使用中最容易忽略的是反馈电阻。 |
|
| [问：] |
请问，如果在增益过零点之前相位已超过360度的系统是稳定的吗？ |
| [答：] |
不稳定。 |
|
| [问：] |
请问：在设计应用系统中如何在提高增益时保证系统带宽？ |
| [答：] |
选用更高增益带宽积GBWP的放大器。 |
|
| [问：] |
请问ADI技术专家：OP2177（OP2177的压摆率为700mV/S，带宽为1.3MHz）工作在巴特沃斯二阶低通滤波器（fcut=1000Hz）并在0dB放大的情况下，其中输入信号峰-峰值：20Vp_p，fin=50Hz。在这种情况下，OP2177能正常工作吗？谢谢！ |
| [答：] |
您给出的数据有误，OP2177的Slew Rate=0.7V/us=700mV/ms=700,000V/s。而不是700mV/s。Slew Rate=dv/dt|max=2*pi*f*Vp. 理论上，只要slew rate大于2*pi*f*Vp，运放就可以正常放大。您的信号要求为（2*pi*50*10=3140V/s），OP2177的Slew Rate指标高于此值，因此可以正常工作。 |
|
| [问：] |
请问电流型高放大倍数（10000000）、高速、低噪音放大器如何设计，选什么器件？ |
| [答：] |
AD8009就是一款高速低噪声电流反馈放大器 |
|
| [问：] |
请问放大生理信号如血压，心电，用什么型号的放大器性价比最高？谢谢 |
| [答：] |
医学应用的仪表放大器，现在ADI主推AD8221. |
|
| [问：] |
请问专家,关于放大器稳定性有没有分析的算法?在那里可找到这方面的资料? |
| [答：] |
稳定性的分析工具是波特图，您可以参考自动控制原理教材和模拟电子技术教材。 |
|
| [问：] |
请问专家,有那些软件可用来对射频功率放大器的稳定性进行分析? |
| [答：] |
安捷伦公司的ADS是一个很好的工具。 |
|
| [问：] |
如果我想采集一个很微弱的信号，是不是差分采样是最好的模式？如果是，那怎么样考虑增加一下差分电路的输入阻抗呢？并请推荐一款适合于差分输入的低噪声且低压供电的运放。 |
| [答：] |
您是对的，差分信号的突出优点就是能够抑制共模干扰。您说的这种放大器实际上是姨表放大器，比如AD620，AD8221等等。 |
|
| [问：] |
如何避免在运放电路中出现震荡,特别是高放大倍数的多级运放中?如果要放大几十万倍，每个放大级的增益如何分配,对补偿有什么特别要求吗？ |
| [答：] |
震荡的原因是相位裕度不足。输入级的电感，以及电容性负载都有可能引起震荡。本次讲座提供了三种可行的方法来提高稳定性。增益的分配，原则是每一级的增益最好均匀分配。 |
|
| [问：] |
如何补偿两个极点之中的零点 |
| [答：] |
Drop it |
|
| [问：] |
如何解决op07 差分放大受温度影响漂移严重? |
| [答：] |
Drop it |
|
| [问：] |
如何用运放组建负采样保持电路？由于偏置电流的影响，经典的采样保持电路好像只能做成正保持的。 |
| [答：] |
Drop it |
|
| [问：] |
如何最小化放大器本身的输出漂移，如果采用补偿电路那种比较好？ |
| [答：] |
请选用采用ADI 自稳零技术的运算放大器，如AD8628, AD8551/2/4, AD8571/2/4,AD8555 |
|
| [问：] |
设计运放过程中，手工运算占一个什么样的地位？因为一些零，极点分析刚你们也说到可能很复杂。 |
| [答：] |
Drop it |
|
| [问：] |
什么叫 rail to rail 放大器 |
| [答：] |
轨到轨放大器，即输入或者输出的电压接近电源或者地 |
|
| [问：] |
什么样的运算放大器能够处理视频传感器输出的信号。 |
| [答：] |
视频放大器一般为高速放大器 |
|
| [问：] |
天津哪里能够您的产品? |
| [答：] |
您可以联系ADI公司的正规代理商：Avnet安富利电子行销公司天津代表处 (022) 23612796；艾睿电子(ARROW TJ)天津代表处 (022) 83191526； |
|
| [问：] |
通过串联电阻是如何提高系统的相位稳定裕量的？ |
| [答：] |
请参考Ask The Application Engineer—32，Practical Techniques to Avoid Instability Due to Capacitive Loading。 |
|
| [问：] |
为何有的data sheet中的测试图显示的相位裕度是负的？与理论中的60度相差很远？ |
| [答：] |
你能举例说明吗？是那个器件的数据手册？ |
|
| [问：] |
为什么单位增益的运放更不稳定呢？ |
| [答：] |
如果你查看运放的开环增益和相位曲线图的话，通过今天幻灯片上介绍的相位裕量的定义和
通过开环增益相位曲线图得到相位裕量的方法，会发现在单位增益的情况下，相位裕量最
小。 |
|
| [问：] |
为什么感性负载会改善相位余量，但是却不常应用？ |
| [答：] |
因为对于大部分的负载它们的特性都是容性的。 |
|
| [问：] |
我们要对pA级的电流做放大，有什么好的方案吗？放大器部分是不是一定要加金属屏蔽 |
| [答：] |
对于pA电流的放大，放大器的Ib要求很高。可以选用JFET或者CMOS输入的放大器。你需要的带宽是多少呢？对于低频的信号，你可以用AD549，AD8601、3、5等等，对于高频，你可以选用AD8067。关于屏蔽，你可以使用guid ring的技术，它在这几个型号的数据手册中能找到。 |
|
| [问：] |
我们做过雷电波峰值表的设计，被测信号的频率集中在3M左右，使用的是贵公司提供的AD9034组成的采样保持电路。为测量负峰值，我们在另一路前面还搭了反向放大器。但信号通过反响放大器时，出现了如刚才所述的震荡，请问用刚才所讲的那三种电路就可以消除么？具体的，用哪种更好些？ |
| [答：] |
那要看你电路的具体形式和选用的放大器。你可以把你的电路发到china.support@analog.com，我们的工程师会根据你的电路推荐补偿方法。 |
|
| [问：] |
我想询问一下ADI有没有关于运放设计以及运放使用的参考资料，谢谢！ |
| [答：] |
请致电800-810-1742索取。 |
|
| [问：] |
我也经常关注贵公司的产品,我想问的是贵公司产品的质量能得到大家的认可
主要是由于什么方面呢(对用户来说肯定是可靠性等),我想问的是贵公司是怎么做到的呢?是在测试上下功夫? |
| [答：] |
dropped |
|
| [问：] |
我曾经用过贵公司的AD629做前级差分放大，后来采购人员反映该芯片不易采购，贵公司是否已停产该芯片？贵公司是否有替代产品？在使用AD629的方案中，发现该芯片很容易损坏，在共模输入电压高（220VAC）的场合，对前级的放大电路，您有何建议？ |
| [答：] |
AD629并没有停产，请与ADI的正规代理联系采购。AD629可以承受+、-270V的共模电压，对于220V肯定没有问题。你可以把你的电路发到china.support@analog.com，我们的工程师会帮你分析你电路可能的问题。 |
|
| [问：] |
现代高频放大器,什么频段叫高频? |
| [答：] |
对于ADI的放大器来讲，通常我们把带宽大于50MHz的放大器叫做高速放大器。 |
|
| [问：] |
一般cmos的运放，由工艺偏差引入的vos大概在什么量级？ |
| [答：] |
由于ADI采用了digi-trim的工艺，CMOS运放的Vos可以控制在几个uV的范围内。 |
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| [问：] |
音频放大电路中，常在反相放大器的反馈电阻上并接一个若干pF的电容，请问这相当于一阶有源滤波器的设计吗？电阻阻值通常根据增益进行选择，那么电容容值根据什么确定呢？ 电路中通常有很多级这样的电路级连而成，这样会形成高阶滤波器吗？对频率和相位的影响如何计算呢？（或分析方法） |
| [答：] |
这个电容形成的低通滤波器的截止频率为1/2piRC。你可以通过你需要的截止频率和反馈电阻的值，得到C值。如果多级会起到多阶的作用。这个电容会补偿系统的稳定性。但是请注意，对于电流反馈型放大器，请不要使用此方法。 |
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| [问：] |
用放大器对外输出电压，为了防止外部高压损坏运放如何采取防护措施？
谢谢！ |
| [答：] |
你所指的高压是输入的吗？如果是，那么可以加箝位二极管。 |
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| [问：] |
有关放大系统的抗干扰问题，您能帮我分析一下常见的问题及其解决方法吗？谢谢 |
| [答：] |
抗干扰最好的方法就是屏蔽。另外对于电源来讲，好的去耦设计也很重要。 |
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| [问：] |
运放电路稳定性除了分析电路的相位裕度还要考虑？ |
| [答：] |
相位裕量直接决定了稳定性。 |
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| [问：] |
运放噪声增益具体是什么概念？好像就是运放正向放大的增益？ |
| [答：] |
是的。 |
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| [问：] |
运算放大器的输出信号上伴随有自激的高频信号或漂移的低频信号,请问如何消除或抑制? |
| [答：] |
请使用几天介绍的这三种补偿方法。 |
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| [问：] |
运算放大器的温漂如何补偿 |
| [答：] |
尽量选用温漂小的放大器，同时放大器电路的电阻的温漂系数也要小。 |
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| [问：] |
在运放的IC设计中应该如何来考虑其参数（偏置电压，长宽比等）的设置？谢谢 |
| [答：] |
dropped |
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| [问：] |
专家您好！前段时间我们开发了一台放大器，其中用到仪表放大器和运算放大器，遇到一个比较棘手的问题：放大器的前端短路（0输入），我想尽量实现0输出，但是效果一直不太好，您能赐教一些好的建议吗？谢谢您 |
| [答：] |
这是由于运放的Vos引起的，可以加上一些电路调节输出的零点。具体方法你致电800-810-1742，我们会把电路发给你。 |
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