How to simulate the gm of XMn1?

[graceice]

The netlist is below，how can i get the gm of XMn1 in hspice ? "gm(XMn1)” can not work here，due to the fact that XMn1 is a subcircuit.


3Ks

***** Transistor Noise model*****
XMn1 o g1 sub sub nnmos L=0.25u W=300u nf=120 sx=1 dx=1
XMn2 g2 g2 sub sub nnmos L=0.25u W=21u nf=8 sx=1 dx=1

 

[yschuang]

I do not quite understand what you said about subckt. A general form of subckt is shown something like
Xbias
mn1 d1 g1 s1 b1 nmos
mn2 d2 g2 s3 b2 pmos
.end
So if you are interested in the gm of mn1, use lx7(Xbias.mn1) or gm(Xbias.mn1).

 

[graceice]

***** Transistor Noise model*****
XMn1 o g1 sub sub nnmos L=0.25u W=300u nf=120 sx=1 dx=1
XMn2 g2 g2 sub sub nnmos L=0.25u W=21u nf=8 sx=1 dx=1

Hi, 3ks.

In the netlist, Xmn1 is a subckt，it is a rf model.

I do not quite understand what you said about subckt. A general form of subckt is shown something like
Xbias
mn1 d1 g1 s1 b1 nmos
mn2 d2 g2 s3 b2 pmos
.end
So if you are interested in the gm of mn1, use lx7(Xbias.mn1) or gm(Xbias.mn1).

Added after 5 minutes:

Xa Vdd Vdd 0 0 n12_ckt_rf Lr=0.13u Wr=5u nf=16

Vin Vdd 0 1.5

.op
.dc Vin 0 1.5 0.01
.print lx7(Xa.MAIN)

I have run this in hspice，but I found the gm=0 when Vin vary from 0 to 1.5V

I can not know the reason.

I do not quite understand what you said about subckt. A general form of subckt is shown something like
Xbias
mn1 d1 g1 s1 b1 nmos
mn2 d2 g2 s3 b2 pmos
.end
So if you are interested in the gm of mn1, use lx7(Xbias.mn1) or gm(Xbias.mn1).

 

[wangyufn]

I think you can get Gm from its definition d(i)/d(V).
Another method is to check the detailed operation point simulation summary, Gm will be listed in it for each transistor.