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ADI笔记,编号为AN-202.关于运放去耦,有些英文和原来不明白

作者：maolei21ic　栏目：模拟技术

ADI笔记,编号为AN-202.关于运放去耦,有些英文和原来不明白
1.It should be apparent that most of the voltage difference
between the AMPLIFIER OUTPUT and the negative supply
appears across the compensation CAPACITOR.

2.If the negativesupply voltage is changed abruptly, the integrator AMPLIFIER will force the OUTPUT to follow the change.
如果负供电电压发生突变,积分运放会强迫输出随之改变.
下面的原理不是很明白.
3.When the entire AMPLIFIER is in a closed-loop configuration the
resulting error signal at its input will tend to restore the
OUTPUT, but the recovery will be limited by the slew rate
of the AMPLIFIER.
当运放闭环运行时,在输入的错误信号会恢复输出,但是恢复会被压摆率限制.
4. As a result, an AMPLIFIER of this type may have outstanding low frequency POWER supply rejection,but the negative supply rejection is fundamentally limited at high frequencies.
因此,此类放大器会有杰出的低频供电抑制,但负电压供电会被限制在高频.
5. Since it is the feedback signal to the input that causes the OUTPUT to be restored, the negative supply rejection will approach zero for signals at frequencies above the closed-loop bandwidth.
由于输入端的反馈信号导致输出恢复,负压供电抑制会由于信号的频率在闭环带宽之上而接近0
6.This means that high-speed, high-level circuits can “talk to” low-levelcircuits through the common impedance of the negativesupply LINE.
这意味着:高速,高电平的电路,通过负压供电线,可以和低电平的电路"对话".

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作者： iC921 于 2006/3/20 0:38:00 发布：

试试吧
2.If the negativesupply voltage is changed abruptly, the integrator AMPLIFIER will force the OUTPUT to follow the change.
如果负供电电压发生突变,积分运放会强迫输出随之改变.
如果负电源电压发生突变,积分放大器会迫使输出跟着改变.

3.When the entire AMPLIFIER is in a closed-loop configuration the
resulting error signal at its input will tend to restore the
OUTPUT, but the recovery will be limited by the slew rate
of the AMPLIFIER.
当运放闭环运行时,在输入的错误信号会恢复输出,但是恢复会被压摆率限制.
工作于闭环的运放,输入误差信号会反映到输出,但是反应速度会受压摆率限制.

4. As a result, an AMPLIFIER of this type may have outstanding low frequency POWER supply rejection,but the negative supply rejection is fundamentally limited at high frequencies.
因此,此类放大器会有杰出的低频供电抑制,但负电压供电会被限制在高频.
因此,此类放大器会有良好的低频电源抑制,但在高频处负电源抑制基本上受到限制.

5. Since it is the feedback signal to the input that causes the OUTPUT to be restored, the negative supply rejection will approach zero for signals at frequencies above the closed-loop bandwidth.
由于输入端的反馈信号导致输出恢复,负压供电抑制会由于信号的频率在闭环带宽之上而接近0
由于输入端的反馈信号可以使得输出重建,因此，在闭环带宽内的信号频率，负电源抑制会接近0

6.This means that high-speed, high-level circuits can “talk to” low-levelcircuits through the common impedance of the negativesupply LINE.
这意味着:高速,高电平的电路,通过负压供电线,可以和低电平的电路"对话".
这意味着:高速高电平电路可以通过负电源线的共模阻抗与低电平的电路"串扰"起来.
（也不太理解）

* - 本贴最后修改时间：2006-3-20 0:41:44 修改者：iC921

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作者： maolei21ic 于 2006/3/20 22:50:00 发布：

去耦的原因:电源对突变的抑制不如正电源的好
Note that the problem with these AMPLIFIERs is associated
with the negative supply terminal. Positive supply rejection
may also deteriorate with increasing frequency, but the
effect is less severe. Typically, small transients on the
positive supply have ONLY a minor effect on the signal
OUTPUT. The difference between these sensitivities can
result in an apparent asymmetry in the AMPLIFIER transient
response. If the AMPLIFIER is driven to produce a positive
voltage swing across its rated load, it will draw a current
PULSE from the positive supply. The PULSE may result in a
supply voltage transient, but the positive supply rejection
will minimize the effect on the AMPLIFIER OUTPUT signal. In
the opposite case, a negative OUTPUT signal will extract a
current from the negative supply. If this PULSE results in a
“glitch” on the bus, the poor negative supply rejection will
result in a similar “glitch” at the AMPLIFIER OUTPUT. While a
positive PULSE TEST may give the AMPLIFIER transient response,
a negative PULSE TEST may actually give you a pretty GOOD
look at your negative supply LINE transient response, instead
of the AMPLIFIER response!
这一段似乎解释了突变的由来,即:由于负电源相对于正电源来说,负电源对突变的抑制不如正电源的好.当放大器产生正电压驱动负载时,将从正电源中汲取电流脉冲,但是正电源良好的抑制比,使得这个顺态干扰不会影响输出信号.

Remember that the imPULSE response of the POWER supply
itself is not what is likely to appear at the AMPLIFIER.
Thirty or forty centimeters of wire can act like a high Q
INDUCTOR to add a high-frequency component to the normally
overdamped supply response. A decoupling CAPACITOR
near the AMPLIFIER won’t always cure the problem either,
since the supply must be decoupled to somewhere. If the
decoupled current flows through a LONG path, it can still
produce an undesirable glitch.
如果去耦电容的位置不好,去耦电流会沿着其它长路流动,突变无法去除

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作者：赤铸于 2006/3/21 2:56:00 发布：

re
1.It should be apparent that most of the voltage difference
between the AMPLIFIER OUTPUT and the negative supply
appears across the compensation CAPACITOR.
放大器输出端和反相输入端间的电压差大部分施加在补偿电容两端

2.If the negativesupply voltage is changed abruptly, the integrator AMPLIFIER will force the OUTPUT to follow the change.
如果负电源发生突变，积分放大器将迫使输出跟随这种变化

3.When the entire AMPLIFIER is in a closed-loop configuration the
resulting error signal at its input will tend to restore the
OUTPUT, but the recovery will be limited by the slew rate
of the AMPLIFIER.
当运放位于闭环电路中时，输入端的误差信号将使输出趋于恢复（恢复到正确状态），但恢复过程会受到压摆率的限制

4. As a result, an AMPLIFIER of this type may have outstanding low frequency POWER supply rejection,but the negative supply rejection is fundamentally limited at high frequencies.
因此,此类放大器会有杰出的低频电源抑制，但负电源抑制在高频下相当有限

5. Since it is the feedback signal to the input that causes the OUTPUT to be restored, the negative supply rejection will approach zero for signals at frequencies above the closed-loop bandwidth.
既然输出的恢复是依靠输入端的反馈信号实现的，对于高于闭环带宽的频率，负电源抑制性能近似为零（因为在高于闭环带宽的频率下反馈信号也很弱了）

6.This means that high-speed, high-level circuits can “talk to” low-level circuits through the common impedance of the negativesupply LINE.
这意味着：高速，高（交流）电平的电路能够通过电源线的公共阻抗和低电平电路发生窜扰
（高频电流流过公共阻抗上产生高频干扰电压，由于负电源高频抑制很弱，就发生了窜扰——窜到其它放大器的输出端）

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作者：赤铸于 2006/3/21 3:10:00 发布：

re
Remember that the impulse response of the POWER supply
itself is not what is likely to appear at the AMPLIFIER.
Thirty or forty centimeters of wire can act like a high Q
INDUCTOR to add a high-frequency component to the normally
overdamped supply response. A decoupling CAPACITOR
near the AMPLIFIER won’t always cure the problem either,
since the supply must be decoupled to somewhere. If the
decoupled current flows through a LONG path, it can still
produce an undesirable glitch.

电源自身的脉冲响应（动态响应）和在放大器（的电源引脚）处看到的不太一样（其实就是说导线阻抗）。30、40cm左右的线类似于高Q值电感，相当于使原本过阻尼（因而较稳定）的电源响应增加了高频成分（可理解为在传递函数上加了个高频项，因而有可能发生振荡）。靠近放大器的去耦电容并不总能解决问题，因为电源必须被“去耦到某个地方”（大概就是电流必须有来有回，构成闭合回路的意思）。如果去耦电流流过很长的路径，同样能产生不利的尖峰干扰（应该是指电流型耦合，或者叫感性耦合）

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作者： maolei21ic 于 2006/3/23 0:20:00 发布：

终于到去耦重点了
1.Figure 3 illustrates three possible configurations for negative
supply decoupling.

2.In 3a, the dotted LINE shows the
negative signal current path through the decoupling and
along the ground LINE. If the load “ground” and decoupled
“ground” actually join at the POWER supply, the “glitch”
on the ground LINEs is similar to the “glitch” on the negative
supply bus. Depending upon how the feedback and
signal sources are “grounded,” the effective disturbance
caused by the decoupling CAPACITOR may be larger than the
disturbance it was intended to prevent.
3a这张图不理解,有更加具体的例子吗?放大器的输出电流是如何流动到"POWEER SUPPLY TERMINAL"上的.
也许我应该这么认为,ACB三点之间我可以看成其它接在正电源和地之间的元器件,信号电流从这些元器件流动.
使得干扰串到负电源上.

2.Figure 3b showshow the decoupling CAPACITOR can be used to minimize disturbance
of V– and ground buses. The high-frequency
component of the load current is confined to a loop that
does not include any PART of the ground path. If the CAPACITOR
is of sufficient size and quality, it will minimize the
glitch on the negative supply without disturbing input or
OUTPUT signal paths.
图3b显示了正确的负电源去耦方法.去耦电容要接在放大器的负端和负载地之间.

3.When the load situation is more complex,
as in 3c, a little more thought is required. If the AMPLIFIER
is driving a load that goes to a virtual ground, the actual
load current does not return to ground. Rather, it must be
supplied by the AMPLIFIER creating the virtual ground as
shown in the figure. In this case, decoupling the negative
supply of the first AMPLIFIER to the positive supply of the
second AMPLIFIER closes the FAST signal current loop without
disturbing ground or signal paths. Of course, it is
still important to provide a low impedance path from
“ground” to V– for the second AMPLIFIER to avoid disturbing
the input reference.
当电流信号如图3C所示流动,当前极放大器驱动后极放大器时,去耦电容接在前一放大器的负端和后一放大器的正端.

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作者： maolei21ic 于 2006/3/23 0:34:00 发布：

模拟电路中,去耦越多,情况越糟糕
1.The key to understanding decoupling CIRCUITs is to note
where the actual load and signal currents will flow. The
key to optimizing the CIRCUIT is to bypass these currents
around ground and other signal paths. Note, that as in
Figure 3a, “SINGLE point grounding” may be an oversimplified
solution to a complex problem.

2.Figures 3b and 3c have been simplified for illustrative
purposes. When an entire CIRCUIT is considered, conflicts
frequently arise. For example, several amplifiers may be
POWERed from the same supply, and an individual decoupling
CAPACITOR is required for each.

3.In a gross sense the decoupling CAPACITORs are all paralleled. In fact, however,
the inductance of the interconnecting POWER and
ground lines convert this harmless-looking arrangement
into a complex L-C network that often rings like the Avon Lady.”
当大量并联去耦电容时,看起来无害,实际上形成了复杂的L-C网络
rings like the Avon Lady.”?????????

4.In CIRCUITs HANDLING FAST signal wavefronts,
decoupling networks paralleled by more than a few centimeters
of wire generally mean trouble.
当电路有高速信号时,在几厘米内并联的去耦电容使得情况更坏.
和数字电路不同吗?数字电路要求每个IC要去耦.

Figure 4 shows how small resistors can be added to lower the Q of the
undesired resonant CIRCUITs. The resistors can generally
be tolerated since they convert a bad high-frequency
jingle to a small damped signal at the op amp supply terminal.
The residual has larger low-frequency components,
but these can be handled by the op amp supply rejection.
解决方法是在负电源和放大器的负电源端接一个小电阻.

8楼：	>>参与讨论
作者： computer00 于 2006/3/23 1:18:00 发布：哈哈，rings like the Avon Lady，此人比较幽默。。。

9楼：	>>参与讨论
作者： 3极管于 2006/3/23 1:28:00 发布：看不懂英文,惭愧

10楼：	>>参与讨论
作者： analogman 于 2006/3/23 11:28:00 发布： Avon Lady是什么意思？

11楼：	>>参与讨论
作者： computer00 于 2006/3/23 12:27:00 发布：查金山词霸，Avon是英国中部一河，像那条河那样振荡（波动）？

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作者： maolei21ic 于 2006/3/23 13:29:00 发布： AVON--化妆品雅芳???

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