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发表于 2011-5-1 16:41:13
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回复【5楼】renpeng009 大鹏集成
能不能说下电容倍增器的具体实现过程，以前还真没学到过。自己大概想了下，想看看是不是正确
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我发现还真没有相关的中文介绍，就算找到的仅有几条资料都是大摆微积分算式，看着就头疼。下面是Wikipedia对其的英文解释，比较浅显易懂我就不翻译了：
Capacitance multiplier
From Wikipedia, the free encyclopedia
A capacitance multiplier mimics a capacitor of different capacitance than the built-in capacitor's.
This is useful in DC power supplies where very low ripple voltage (under load) is of paramount
importance, such as in class-A amplifiers.
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Transistor based
A basic capacitance multiplier.
Here the capacitance of capacitor C1 is multiplied by the transistor's current gain (β).
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(原文件名:tr.jpg)
R1 and C1 form a low-pass filter and help smooth any ripple in VS. R1 supplies the charging current
as well as the transistor's (denoted by Q) base current. R2 is the load on the circuit. Without
Q, R2 would be the load on the capacitor and C1 would have to be very large to maintain low ripple.
With Q in place, the loading imposed upon C1 is simply the load current reduced by a factor of β.
Conversely, C1 appears "multiplied" by a factor of β to the load.
Note that this circuit is not a voltage regulator, since the output voltage varies directly with
the input VS. The output voltage is about 0.65V less than the base voltage, which in turn is about
2–3 V less than VS (when loaded). Larger values of R1 (and C1) reduce the output ripple to almost
negligible levels. On the downside this causes the output to rise slowly towards the required value
(especially when the load is connected), due to the larger time constant of R1 and C1.
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Operational Amplifier based
A basic capacitance multiplier.
Here the capacitance of capacitor C1 is multiplied by the quotient of the resistances of R1 and R2.
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(原文件名:op.jpg)
能翻_墙的看这里：http://en.wikipedia.org/wiki/Capacitance_multiplier |
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发表于 2011-5-1 16:04:59
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发表于 2011-5-1 16:12:34
