求教：运放的输入管的gm的问题

Usually we use large W/L ratio for input transistor of OPA to overcome mismatch and noise. Given the bias current, large W/L will push input transistor into weak inversion. Therefore, Gm will be nI/Vth, NOT sqrt(2KWI/L). I suggest to calculate Gm in weak inversion by hand instead of strong inversion.

谢谢liliang.gu但是你说的nI/Vth 这个n是什么意思?

n=1~2, Vth=kT/q

n=1~2, Vth=kT/q

i/(n*vth)

Exactly！

请看Willy Sansen的书
《analog design essential》

降低噪声的需要

假如是为了减少offset的话，工作在weak inversion状态并不推荐；

应该是降低噪声，提高匹配的原因吧～～～～

check your devicein the saturation region?

DDDDDDD