CMOS operational amplifier design

Thread Starter


Joined Jun 16, 2007
Hello Friends,

I'm taking an electronics course this semester and i got to do a small homework project like for this course..

the amplifier is a differential input single ended cmos op amp

it has to meet the following specs as in the figure

I should use a positive +VDD/2 supply and a negative –VDD/2 supply only.

The requirement to have VOS = 0 V means that there should be no differential mode offset; for a 0 V differential input and a common-mode input at the midpoint of the common-mode input range, the output should be 0 V under nominal supply conditions.

I am free to choose the midpoint of the common mode input range.

The available components are: NMOS transistors, PMOS transistors and resistors. Ideal sources can only be used to generate the supply voltages, not to generate bias currents.

Device Models

The device models are encapsulated in a sub-circuit; use:

x1 d g s b nmos w=10u l=0.13u
x2 d g s b pmos w=10u l=0.13u

The sub-circuit definitions are as follows:

.subckt nmos d g s b params: w=10u l=0.13u
m0 d g s b nmos_internal w={w} l={l}
.model nmos_internal
+ nmos level=1 kp=500u vto=0.3 gamma=0.2 phi=0.6
+ ld=0.025u
+ lambda={0.2*exp(0.13u/{l})/exp(1)}

.subckt pmos d g s b params: w=10u l=0.13u
m0 d g s b pmos_internal w={w} l={l}
.model pmos_internal
+ pmos level=1 kp=120u vto=-0.3 gamma=0.2 phi=0.6
+ ld=0.025u
+ lambda={0.15*exp(0.13u/{l})/exp(1)}


i'm finding this very difficult to achieve

i tried something on a draft and is as follows:

am i close to something ??? any suggestions ?? how to assign a value for every transistor ?

how to complete the schematic ?? and examples close to what i'm going to do

thank you in advance


Joined Jan 7, 2010
i dont really know act.. but, i have read it.. try to get reference from book CMOS Analog Circuit Design. Philip E. Allen & Douglas R Holberg..