Calculating output swing of amplifier

[Sambhav_1]

Hi

I am designing an amplifer and finding issues in calculating the output swing.
I am connecting the positive output(vout1) to negative input and sweeping in from -2 to 3V. But after cecrtaing value the output is getting saturated. Kindly help with this. I am trying to get 2.5V differential swing .

Thanks

 

[wwfeldman]

as i read your circuit, vdd is 1.8V
the simulation shows the output at 1.73 V
that's the best you're going to do

you can't get more out than you put in
- in this case, the power you are putting in is at 1.8V, so the output will get close to 1.8V but never exceed it.

i think you will also notice that the signal to be amplified does not get amplified until it is greater than 0V
because you are powering the circuit between 0V and 1.8V, other voltages below 0V will not have the desired effect

 

[Sambhav_1]

as i read your circuit, vdd is 1.8V
the simulation shows the output at 1.73 V
that's the best you're going to do

you can't get more out than you put in
- in this case, the power you are putting in is at 1.8V, so the output will get close to 1.8V but never exceed it.

i think you will also notice that the signal to be amplified does not get amplified until it is greater than 0V
because you are powering the circuit between 0V and 1.8V, other voltages below 0V will not have the desired effect

so is this the correct response?

 

[martinnl]

Are you taking the vout1 from the gate of one of the pmos transistors in the differential pair?