[转]几道analog面试题

no4ing

学习中。。。

kevin_xiao

我们没学过Ra的书，哎，只学过模拟电路。准备看看拉杂维的书了。

zc14052050

看不懂

sandkowa

very good stuff

babbage

there are 3 kind of offset: loop offset, system offset and random offset. In this, random offset is major, many material study this.So some simple word is hard to explain this. If you want to be one good designer, u should study this carefully and consider this when you design one differial pair.

fanda100

好帖，长见识！希望高手多发发！

mulder

谁家的面试题？

xwlpxc

拉查维的书以前看得太肤浅，记录了，领教了

hlbecky

学习学习了，谢谢！

Distance_He

For the sake of stability, the gm of second stage is always larger than first stage, usually 8-12 times larger.
To get a PM of 72 degree(no overshoot in frequency domain, only alittle overshoot in time domain but better settling time performance),we need fnd = 3GBW. If you calculate, you will get such expression:gm2/gm1 = 4Cl/Cc. Cc is usually 2-3 times smaller than Cc. Then gm2 is8-12 larger than gm1. Sansen told us in class that when you design anOTA, increasing the current in the second stage will always solve theproblem, but at the cost of power. You can reference the book "Analogdesign essentials" by Willy Sansen, he introduce the design of OTA inchapter 6,7,8.
PMOS has better performance in noise. But use PMOS as the input willintroduce doublet problem. You will find poles and zeros too close toeach other which will affect your time domain applicaion in settlingtime a lot. Furthermore, fT of PMOS is lower than NMOS, which willlower the speed of your circuit.