Please Help: CMOS Common Source Amplifier

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justsunny

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Dear All,

I am new in Analog CMOS IC design.
I am trying to design the following amplifier in CMOS 180nm technology in cadence.

1. How do I calculate the W and L for all transistors ?
2. How do I calculate the gm1 of nmos(M1) and gm2,gm3,gm4 of pmos(M2.M3,M4) ?
3. How do I calculate Vtn, Vtp, UnCox, UpCox and channel length modulation factor for both nmos and pmos

Supply voltage is 6 V and gain has to be -1000.

Please Help.
Thanks.
 

You need one more input parameter to calculate your W and L, that is the current.

For example, the current is 10uA.

M3,M4 and M5 are diode connected.
In saturation mode:
Ids3=Ids4=Ids5 --> Vdssat3=Vdssat4=Vdssat5 -->Vsg3=6V/3=2V.
(W/L)3=(W/L)4=(W/L)5 will be calculated by
Ids = (1/2)*k*(W/L)*(2V - Vt)^2
Where k, and Vt you can get from Model file.

For M1:
Vdssat = Vin - Vt

gm1~ k *(W/L) * Vdssat
ro1 ~ 1/(lamda*Ids)

Gain = gm1 * (ro1//ro2)

From Gain = 1000 --> you could calculate (W/L)1

Good luck!
 

How do i calculate the value of lamba (channel length modulation fator ) for both pmos and nmos in 180nm CMOS ? is the value of lambda a constant for pmos and nmos ?

Thanks.
 

Hi justsunny,

The lamda is not a constant value, you could find the equation for this parameter in BSIM manual document. Currently, the related parameter in model file is PCLM.
In the past, you could find the value of lamda @ level 1/2 of model file. But now, my suggession is to run simulation with L ~ 1um/10um and Vds ~ 1/2Vdd then measure the lamda from I_V plot. By this way, you can get an acceptable value of lamda using for your hand calculation.

Best Regards,
 

    J

    justsunny

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