# Gyrator implementation of chip inductor

1. ## Re: Gyrator implementation of chip inductor

Originally Posted by promach
@Ata_sa16

Vc is the voltage node name for V(in) of the following Gm2 circuit block.

Why does Vc drops from around 2.9V to 1.8V ?

Attachment 140634

The exact Gm2 equation as discussed in https://www.reddit.com/r/chipdesign/...chip_inductor/ is as follows:

Attachment 140635
I dont have any idea.

That is true. You have to write approximate equations in order to understand the circuit behavior not getting stuck in detailed small signal calculations.
in that formula if ro is high, gm4=gm3 and rd=1/gm3 (since ro3 is high), again you will reach Gm=gm1 as i wrote earlier.

2. ## Re: Gyrator implementation of chip inductor

Regarding transconductance values determination, should I use manual calculation or simulation ? As for transconductance simulation, how would I do it ? in AC small-signal simulation ? I could not find any spice examples on transconductance measurement.

3. ## Re: Gyrator implementation of chip inductor

for BSIM3v3 NMOS model as in http://sprunge.us/EGHI or below , how do I find out which parameter is the transconductance, gm ?

There is no documentation regarding this at http://ngspice.sourceforge.net/exter...330_manual.pdf

*model = bsim3v3
*Berkeley Spice Compatibility
* Lmin= .35 Lmax= 20 Wmin= .6 Wmax= 20
.model N1 NMOS
+Level= 8
+version=3.3.0
+Tnom=27.0
+Acnqsmod=1 elm=3
+Capmod=3
+Nch= 2.498E+17 Tox=9E-09 Xj=1.00000E-07
+Lint=9.36e-8 Wint=1.47e-7
+Lintnoi=1e-9
+Vth0= .6322 K1= .756 K2= -3.83e-2 K3= -2.612
+Dvt0= 2.812 Dvt1= 0.462 Dvt2=-9.17e-2
+Nlx= 3.52291E-08 W0= 1.163e-6
+K3b= 2.233
+Vsat= 86301.58 Ua= 6.47e-9 Ub= 4.23e-18 Uc=-4.706281E-11
+Rdsw= 650 U0= 388.3203 wr=1
+A0= .3496967 Ags=.1 B0=0.546 B1= 1
+Dwg = -6.0E-09 Dwb = -3.56E-09 Prwb = -.213
+Keta=-3.605872E-02 A1= 2.778747E-02 A2= .9
+Voff=-6.735529E-02 NFactor= 1.139926 Cit= 1.622527E-04
+Cdsc=-2.147181E-05
+Cdscb= 0 Dvt0w = 0 Dvt1w = 0 Dvt2w = 0
+Cdscd = 0 Prwg = 0
+Eta0= 1.0281729E-02 Etab=-5.042203E-03
+Dsub= .31871233
+Pclm= 1.114846 Pdiblc1= 2.45357E-03 Pdiblc2= 6.406289E-03
+Drout= .31871233 Pscbe1= 5000000 Pscbe2= 5E-09 Pdiblcb = -.234
+Pvag= 0 delta=0.01
+ Wl = 0 Ww = -1.420242E-09 Wwl = 0
+ Wln = 0 Wwn = .2613948 Ll = 1.300902E-10
+ Lw = 0 Lwl = 0 Lln = .316394
+ Lwn = 0
+kt1=-.3 kt2=-.051
+At= 22400
+Ute=-1.48
+Ua1= 3.31E-10 Ub1= 2.61E-19 Uc1= -3.42e-10
+Kt1l=0 Kt1=-0.1 Prt=764.3

•

4. ## Re: Gyrator implementation of chip inductor

how do I find out which parameter is the transconductance, gm ?
None of it particularly. As you know, gm is operation point dependent, the actual circuit operation point and many of the listed level 8 model parameters affect gm.

5. ## Re: Gyrator implementation of chip inductor

@FvM

However, the mosfets are not in saturation all the time since the input to the CMOS inverter is a sinusoidal wave as shown below:

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