gm/ID
優(yōu)點(diǎn)：直接和VGS-VTH 對(duì)應(yīng)，查找表，短溝道，亞閾值。
長(zhǎng)溝道模型：
截止區(qū)：ID = 0。
線性區(qū)：Ron，ID = \frac{1}{2}uCoxW/L[2(VGS-Vth)VDS-VDS^2]
飽和區(qū)：ID = 1/2uCoxW/L(Vgs-Vth)^2
gm/Id = 2/(Vgs-Vth)
transit frequency fT =? 1/2pi gm/Cgs , Cgs = 2/3 Cox WL? ?
傳統(tǒng)設(shè)計(jì)方法
假設(shè)Vov = 300mV， ID = 1mA；Vout = -vin gm 1k, gm = 2ID/Vov = 2.1mA/300mV = 6.7ms
Av = -gmRL = -6.7ms.1k = -6.7, 帶寬500Mhz, Av = 10
gm = 10/1k = 10ms，Cgs = 1/2pi/300/500M = 1.1pf
fT = gm/cgs/2pi?= 9.4G。?
可以知道Vov, gm/Id, Id
?gm/Id 與fT
500Mhz， 10
gm?= 10ms
Cgs = 1/2pi/300/500 = 1.1
ft = gm/2pi/cgs = 9.4G
gm/Id <17.5
Id = 570u
確定L。確定W
W不影響，gm/Id，ft。影響Cgs, Id
https://picture.iczhiku.com/resource/eetop/syirgiALKqjZpnCV.pdf
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