m**a
发帖数: 464 | 1 各位大牛，求问一个pole怎么解。
电路很巧妙，推导了之后求transimpedance gain什么的都挺简单的，但我就是不会求
这个pole了。
原paper里只是直接说了一句3dB BW在(1+A)gm/C2.
有一篇斯坦福的论文引用了这篇文章，推了很复杂的一堆，我觉得应该没这么难呀，解
一堆二次方程什么的。
原paper：
B. Razavi, “A 622Mb/s 4.5pA/√Hz CMOS transimpedance amplifier,”
ISSCC Tech. Digest,San Francisco, CA, Feb. 7-9, 2000, pp. 162-163.
斯坦福的paper：
A 56MΩCMOS TIA for MEMS Applications
电路在附件
先说谢谢了 | h********t
发帖数: 555 | 2 Assuming the poles of the OpAmp and 1/(Cload*Rd) are located at high
frequency, then 3db bandwidth of the circuit you are showing is determined
by R and C of the node vx.
if you ignore cp, (assume cp is 0), the output resistance looking into vx is
1/((1+A)*gm). Capacitance load is C2. pole = 1/RC=(1+A)gm/C2
Note: if we ignore Cp, the equivalent load capacitance to Vx is C2 only. The
reason is simple. if you apply at test current source at vx, the current
won't go to C1, because it is assumed Isig has infinite output impedance. So
, C1 does not load Vx node.
what if we must include Cp? Then C1 and Cp will also load Vx.
the output resistance looking into vx is (C1+Cp)/C1 *[1/((1+A)*gm)].
This is because Cp reduces the loop gain by a factor of (C1+Cp)/C1 , so
output resistance increases by a factor of (C1+Cp)/C1 .
capacitive load at vx becomes C2 + C1*Cp/(C1+Cp)
3db pole = 1/RC=(1+A)gm/[(C1C2+C1Cp+C2Cp)/C1]
if Cp -->0, it becomes (1+A)gm/C2 | m**a
发帖数: 464 | 3 谢谢大牛，包子已发：）
determined
is
The
So
【在 h********t 的大作中提到】
: Assuming the poles of the OpAmp and 1/(Cload*Rd) are located at high
: frequency, then 3db bandwidth of the circuit you are showing is determined
: by R and C of the node vx.
: if you ignore cp, (assume cp is 0), the output resistance looking into vx is
: 1/((1+A)*gm). Capacitance load is C2. pole = 1/RC=(1+A)gm/C2
: Note: if we ignore Cp, the equivalent load capacitance to Vx is C2 only. The
: reason is simple. if you apply at test current source at vx, the current
: won't go to C1, because it is assumed Isig has infinite output impedance. So
: , C1 does not load Vx node.
: what if we must include Cp? Then C1 and Cp will also load Vx.
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