help on use nwell resistor

[plz762127]

*0005cs amplifer gain
.OPTIONS POST=2
M1 VOUT VIN GND GND NMOS_3P3 W=7U L=0.35U
XRD1 VOUT VDD VDD NWELL R_LENGTH=50U R_WIDTH=5U
*R1 VOUT VDD 8.5K
VDD VDD GND DC 3.3
VIN VIN GND DC VDC1 AC 1
.PARAM VDC1=0.5
.OP
.AC DEC 100 1 10G SWEEP VDC1 POI 7 0.5 0.75 1 1.25 1.5 1.75 2
.LIB 'C:\synopsys\Hspice_Z-2007.03\zhouxiaoqiu\sm046005-1d.hspice' typical
.END
When I use R1 VOUT VDD 8.5K instead XRD1 VOUT VDD VDD NWELL R_LENGTH=50U R_WIDTH=5U it is all right
I think the use of nwell is wrong ,how to use it
this is the part in Chartered .35
.subckt nwell 1 2 3 r_length=50u r_width=5u
*****************************************************************************
* Nwell diffusion unsalicided resistor model
*****************************************************************************
.param r_rsh0= 850
.param r_dw= -1.838e-7
.param r_dl= 0
.param r_l='r_length-2*r_dl'
.param r_w='r_width-2*r_dw'
.param r_n='r_l/r_w'
.param r_tnom=25
.param r_vc1=0
.param r_vc2=0
.param r_tc1=3.57E-03
.param r_tc2=1.09E-05
.param r_area = '0.5*r_length * r_width'
.param r_peri = 'r_length + r_width'
.param r_temp='1+r_tc1*(temper-r_tnom)+r_tc2*(temper-r_tnom)*(temper-r_tnom)'

*/ model for substrate capacitance
.model r_dsub d level=3 Cj=1.71E-04 Mj=0.23 Pb=0.61 Cjsw=4.76E-10 Mjsw=0.317 Php=0.619 tref=25

*/ terminal 1
d1_r 3 1 r_dsub area = r_area pj = r_peri
*/ body
rbody_r 1 2 r='r_temp*r_n*(r_rsh0+r_vc1*abs(v(2,1))/r_n+r_vc2*abs(v(2,1))*abs(v(2,1))/r_n/r_n)'
*/ terminal 2
d2_r 3 2 r_dsub area = r_area pj = r_peri

.ends nwell
*/
*/

 

[keith1200rs]

Hmm. I am not sure I can help much, other than to say that my simulator (not Hspice) will not accept a circuit dependant variable as a parameter in a resistor. I guess Hspice will otherwise you would get an error.

I would try a simple voltage source & the resistor and sweep the voltage and measure the current. That will give you the resistor value and help track down the problem.

Keith.

 

[cmos80]

XRD1 VOUT VDD VDD NWELL R_LENGTH=50U R_WIDTH=5U

is the correct way.