[SOLVED] OTA output saturation range

[Junus2012]

Dear All

I am simulating the output swing saturation regionof my OTA . I am using cascode load so I was expecting to get limited out swing due to the cascodse but I surprised that I am getting approxiametly rail to rail output saturation range.

The method I am using to simulate the output range is by connecting the OTA as an inverting amplifier with gain 10, the input voltage is in the range if the ICMR so it will affect the output properties.

do you have any reason to explain my case?
Thank you

 

[FvM]

There are different cascode current mirror variants in use, some have low "saturation" voltage. You'll know the answer if you analyze the circuit details.

 

[Junus2012]

Hello FvM

I am not using the wide swing cascode voltage. any way I came to know the reason. When I see the output voltage it seem to be linear but if I take the derivative by the calculator and looking for the area where the closed loop gain is at the desired value I would see the real linear region as you can see in the attached image. So I was tricked by the output signal

 

[FvM]

You have ben asking about output swing, not linear range of the transfer characteristic. The latter is already limited by the differential pair input stage,