in Hspice , what is “beta”??

hspice beta

I designed simple Cs amp wit active load.

follow is list file

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element 0:mm1 0:mm2 0:m1
model 0:pch.13 0:pch.13 0:nch.18
region Saturati Linear Saturati
id -1.5309m -1.4281m 1.4280m
ibs 1.205e-20 1.125e-20 -2.331e-20
ibd 2.8036f 5.627e-19 -50.8288n
vgs -7.4691 -7.4691 3.0000
vds -7.4691 -5.6078 3.3922
vbs 0. 0. 0.
vth -810.8161m -816.3119m 610.4944m
vdsat -6.5832 -6.5757 1.5230
beta 72.3651u 72.4344u 777.8039u
gam eff 519.9555m 519.9558m 866.6245m
gm 249.4204u 153.1575u 812.7456u
gds 25.8188u 99.2249u 9.2181u
gmb 363.3548u 275.5685u 196.8015u
cdtot 4.1028f 4.3392f 8.0071f
cgtot 14.4586f 14.4634f 23.1583f
cstot 20.6489f 20.6520f 32.0798f
cbtot 9.5857f 9.8074f 21.4919f
cgs 16.2329f 16.2228f 19.9898f
cgd 946.4484a 953.2504a 1.8745f

I dont' understand what is mean "beta".

it mean "K" in mosfet current equation or "K'" ? or otherwise?

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beta is the transconductance coefficient.

in simulations, beta is one of the parameter used in MOSFET SPICE modeling.

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beta is product of
µCox and (W/L)

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I got another question.
What is Vdsat in the .lis file?
saturation voltage? over-drive voltage?

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vdsat=vgs-vth
beta=K*(w/l)

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Vdsat = vgs - vth??

but above lis file, vgs= 3 , vth = 0.610 , vdsat= 1.5230

vgs - vth = 2.39 ... but vdsat = ?? 2.39 = ?? = 1.5230??

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Vdsat is the minimum Vds requried to keep the tansistor in saturation.

Opamp741 reffered to Vgs-Vth u use to calculate the current for MOS in saturation.

Correct me if I am wrong Opamp741

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But when Vds> Vgs-Vth, the mos enter into saturation. Why Vdsat does not equal to Vgs-Vth?

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IN square-law IDS equation, when vds>vdsat=vgs-vth, the transistor enter Saturation. The conlusion is derived from quadratic equation's maximum valus. but in level3 or BSIM3 model, the relation between IDS and VGS, VDS, VBS is not simple square-law. there exits the maximum value of equation in linear region, from which we can get vdsat, and this vdsat is not exactly the same as VGS-VTH. a coeffient n usually included: Vdsat=(VDS-VTH)/n, n just a experience factor.

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Vdsat is when a mosfet enters saturation region. For Long channels, VDsat = (Vgs - Vth) but as the channel length shrinks VDsat is no longer equal to Vov as a lot of secondary effects kick in.