How to make sure the transistors in saturation region?

[hbsustc]

Hi, all.

I use ADS to simulate the AC response of this gain-boosting amplifier as the following figure (please see the attachment), but it is verypainful to choose the comfortable voltage Vref and Vin if I use the simple DC-source or DC parameter in AC-source in order to make sure M1 and M2 in saturation region. Because of the current-source Id, the Vd and Vout is very large when I set the Vin and Vref from 0.5-0.7V. Maybe
there is effective ways to find the right Vin and Vref such as connecting one large resistance between the Vref and the Vout node?


Looking for the help from everybody.
Thank you very much indeed..

 

[DenisMark]

U need to utilize negative feedback to stabilizate operation point. Some example of testbench i've attached. Due to negative feedback u can stabilize operation point of M1 and do proper AC analysis.
Testbench requeres to set VOUT_DESIRED, it is some VOUT value in expected output range. U can do AC sweep regarding VOUT_DESIRED to define output swing range (criterion is gain decreasing on 3dB)

 

[hbsustc]

Thank u very much, i will try