I am designing a folded cascode using the sky130nm pdk and came across a odd phenomenon.
In the picture below , you can observe the intrinsic parameters i obtained in the operating point
Based on this , and assuming gain is gm3 ( gm1/gds1 (1/gds3+gds2) ) ( M4 and M5 cascoded current source has high impedance ) , the gain would be around 65 dB.
However , when running AC simulation , i got 45 dB which is substantially lower
I tried to debug this by looking at the output impedance and its value is 10 times lower hence it could explain the difference observed in the gain.
Now the question is , should i not trust the intrinsic parameters ? Why is there such a difference ? How could I solve this issue ?
Hi everyone
I am designing a folded cascode using the sky130nm pdk and came across a odd phenomenon.
In the picture below , you can observe the intrinsic parameters i obtained in the operating point
Based on this , and assuming gain is gm3 ( gm1/gds1 (1/gds3+gds2) ) ( M4 and M5 cascoded current source has high impedance ) , the gain would be around 65 dB.
However , when running AC simulation , i got 45 dB which is substantially lower
I tried to debug this by looking at the output impedance and its value is 10 times lower hence it could explain the difference observed in the gain.
Now the question is , should i not trust the intrinsic parameters ? Why is there such a difference ? How could I solve this issue ?
I am using ngspice42
Thanks for the help in advance, Alex