For a prototype OpAmp below $($differential amplifier cascaded with Common$-$emmiter and Common$-$Drain$),$ given VDD$=6$V$,-$VSS$=-6$V$,$ IREF$=0\mathrm{.}4$mA$,($W$/$L$)1=($W$/$L$)5=5.$ design requires IO$2=2$mA$,$ IO$3=2$mA$,$ IO$4=10$mA$,$ assume all MOSFET transistors have $=0\mathrm{.}02/$V$,$ and given gm$2=$gm$6$

$=$gm$7=$ gm$8=5$mS$,$ gm$9=8$mS$.$ For MOSFET ro$=(1/$ $+|$VDS$|)/$IDS

At quiesent condition $($v$1=$v$2=$vo$=0),$ VGS$1=$VGS$21\mathrm{.}7$V$,$ Vds$63$V$,$ Vds$36$V$,$ and Vds$4=6$V$.$

For PNP transistor Q$12,$ assume $|$VBE $|0\mathrm{.}7$V$,$ $=100,$ VA$=50$V$.$

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If the current source IREF is implement by a resistor, determine the value of the resistance in Kohm.