Hello!
I have to analyse and if necessary optimise this circuit. **broken link removed**
Technology of the circuit is at0.35n
When I connect it as voltage follower and simulate with spice I get response like this: **broken link removed**
Why the output don't follow the input until 0.7V. Is this because of the treshold voltage of m1 and m2? Can I fix it in some way or only with changing substrate doping?
Parameters of this transistors are:
m1 w_6 inn w_1 vssa MODNm w=50U l=12U m=6 ad=55P as=55P pd=52.2U ps=52.2U nrs=8M
+ nrd=8M
yes it is.
It is not 'strange characteristic', it is normal.
your circuit isnt designed as rail-to-rail input characteristic.
Many op-amp desiged in this metod. you can search internet for rail-to -rail
(input) op-amp. for example get some datasheet of rail-to-rail op-amp schematic
and evaluate its circuits.
yes,the result is right.
do you simulate the CMR of the opa?
it is no much useful to change the doping.
the most is rail to rail, as Davood Amerion said.