[Moved] Problem with the output in a gilbert cell multiplier design

[m.afzal]

I am a first time analogue designer and need help with my Gilbert cell multiplier(CMOS 0.18um technology). The problem is that my circuit doesn't bias correctly.I work in low frequency. the output that I need, the plot of four quadrant of multiplier.

*Gilbert cell analog 5
.options brief
*********************Main circuit**********3
m1  n1 x1 n4 n4 n  L=0.18u   W=50.12u    
m2  n2 n3 n4 n4 n  L=0.18u   W=50.12u 
m3  n1 n3 n5 n5 n  L=0.18u   W=50.12u 
m4  n2 x1 n5 n5 n  L=0.18u   W=50.12u 
m5  n4 y1 n6 n6 n  L=0.18u   W=100.24u 
m6  n5 y2 n6 n6 n  L=0.18u   W=100.24u 

R1 n1 n12 500
R2 n2 n12 500
**********************load library******************13
.lib 'C:\synopsys\Hspice_A-2008.03\mm018.l' tt 
 *****************define stimuli ********************15   
vx1 x1 0 dc=0.6v
vx2 n3 0 dc=-0.6v 
vy1 y1 0 dc=0.4v   
vy2 y2 0 dc=-0.4v 

vdd n12 0 dc=1.8v
vss n6 0 dc=-1.8v

vx	x1	n3     0.2v	
vy	y1	y2	
*************** DC sweep statements **************27      
.op
.dc         vy   -1v     1v    0.5v	     
.probe	dc	v(n1,n2)
.end

 

[erikl]

To get help, instead of the netlist better show your schematic (incl. the test bench).