regulated cascode help

[sharkies]

I have a simple regulated cascode.
I tried to get the gain of the loop transfer function, but this is what I get.
Am I simulating this wrong?
The transfer function should be coming out as a low-pass filter shape, but it's not.
I'm feeding a AC source and take the output right before the inductor

Also, I'm running the regulated cascode transistor(the aux amp) in subthreshold since the Vgs is only .2V , Is this Ok? when I check the output of the aux amp, it seems fine, It's only when I check the output at the inductor things seem screwed

 

[prcken]

maybe the dominant pole is very small, what's the start point of the AC sweep? 700Hz?

 

[erikl]

may be the dominant pole is very small ...

The dominant pole is probably 1/2π√LC ≈ 0.16 Hz ?

 

[windknows]

both the vbias and I15 are going to set the vgs of the M46. how do you match them?
and maybe the value of the L,C should be more larger to set the complex pole/zero couse by the LC to smaller frequency

 

[sharkies]

I15 has just enough current so that the Drain of M45 will be .8V.
I'm still lost as to what is wrong with my schematics here...
How do you guys break your loop?

 

[windknows]

did you check the region of the cascode? (since you have mentioned the output of the aux amp is fine)
i still think you have to match the vbias for the I15...