转自:中电网

1. 双电源运放和单电源运放有多啥差别？对双电源运放我能用单电源吗，会照成什么问题吗？谢谢！
In theory, no matter single or dual supply, the op amp actually care the voltage range it operates. In reality, usually the single supply op amp can work at a narrow voltage range, e.g. 0V to 5V and dual supply op amp needs a wide operating voltage range. When using a dual supply op amp at single supply, pay attention on the CMVR and the output swing that the op amp can operate properly.  
2.在弱信号放大器中，如何降低电源引起的噪声？如何保持信号放大后的不失真？
Please try to use de-coupling cap to reduce power supply noise. During the layout, please place these cap as close as the V+ pin as possible.
Also, you may try to put guard-ring on the pcb at the pos / neg input pins.
If it"s possible, try to use 2 stages of opamps instead of one opamp. With min gain of the 1st opamp or called "preamp", the distortion can be less significant to your system.  
3.怎么样加入短路保护功能？
Usaully the short circuit protection circuit is built inside the op amps but only some have it. Pls check the datasheet to see if the op amp you choose with the protection circuit built-in.  
4.请问当放大器放大线性度不好时应如何调节
It really depends on the op amp circuit design. You may need to choose an op amp with better Harmonic Distortion spec. But limiting the input signal to the Analog ground will help improve the linearity of the output signal.
 
5.运算放大器的负载能力与哪些因素有关？如何提高运算放大器的负载能力？
The output capability of an op amp depends on the output stage circuit design. In case you really need to drive a heavy load, we recommend that you should use an external transistor.
6.请专家讲解一下什么叫"轨至轨"?谢谢！
Rail-to-Rail input means that the op amp can work with an input signal coming from very close to or equal to both the +ve supply rail and -ve supply rail.

Rail-to-rail means that the op amp can output a siganl swing very close to both the +ve supply rail and -ve supply rail.
The Rail-to-rail feature is important in the single supply (i.e low voltage) applications.
 
7.请说明提高转换率的方法.是否需要外接另外一个运放来获得更好的驱动能力
The slew rate is fixed for a particular op amp once its design is finished.
Usually op amp is designed for signal conditioning but not for driving very high current. Power transistor or specific amplifier (e.g. Audio amp like our Boomer series) are recommend for high power applications.
 
8.放大器设计工具对元件的分布参数/寄生参数有何考虑?  
These data is not included in this webench tool because parasitic parameters always releated to your pcb material...number of layer, trace width, etc. These uncertain is not completed..also not important for you to start design at the very beginning stage.
 
9.双极运放和CMOS运放在性能有何差别?
Biploar op amp usually has a lower input impedance and high input bias current, high current noise, also has a faster speed.
CMOS op amp usually has a higher input impedance and lower input bias current, high voltage noise, lower speed (BW) but consume very low current.
 
10.請問如何有效的實際測量op的特性
All of the IC from our company are tested before we ship out. Basically, datasheet/spec is a very good reference for device performance. The actual measurement can be done by customer depends on the actual configuration. In general, I will suggest to use as buffer / voltage follower to test the opamp.
11.如何提高低功耗运放的负载能力？谢谢！
Low power op amp means it "Quiescent current" (i.e. no load) is very low, say a few uA. When it is used to drive heavy low - high current output, the low quiescent current will not make sense any more. Therefore, low power op amp usually cannot support high output.
 
12.在电路设计时使用运算放大器，基本的原则是什么？需要注意那几方面的问题？
Just brifely.
Power supply range.
Input range.
Output range.
Gain of the amplication
Output loading
If RRIO is needed?
enough GBWP to cover whole freq range...  
13.如何减少差分输入的信号干扰 ?
Try add guard-ring at the positive & negative inputs of the opamp when you design your PCB layout.
 
14.运算放大器用于微伏级信号放大，如何解决放大倍数和噪声控制？
Try to use small gain only for the preamp stage in order to protect the input signal before the real gain stage...mean two stages of opamp is the solution for very small input signal. Also, choose low noise part number..
Suggestions: lmv721, lmv722, lmv751, lmv771, lmv772 & lmv774.
 
15.在什么情况下,需要特别注意运放的CMRR和PSRR参数?  
CMRR is the ratio of the offset voltage over common mode voltage. As a result, be carefull if you have large offset opamp with small common voltage inputs.
 
16.用运放组成的有源滤波器和数字滤波器相比,有何差别和优缺点?
For some simple (low order) filter, active analog filter is easy to implement and low cost. But high order active analog filter design can be very difficult.
In implementing Digital filter, you need to converter the analog signal to digital signal first and also you need to have a MCU or DSP to do all the calculation. That could be expensive.