How to Design a two-stage high-speed op-Amp using equations?

I wanted to design a High-speed Op-amp,i referred text book like Allen.Holberg.

But i am not meeting my Specification,I am using Tanner S-edit for simulation results.

After calculations the overall gain is 70v/v,but according to my specification it is 3000v/v,really i am out of my domain .

Plz can any one help me out, and is there any other method or Text which describes the actual calculation for designing a two-satge High-speed Op-amp....

I am working on 250nm technology and included some of the model parameters calculated...

Some of the parameters calculated are::

K'n= Un*Cox= 284.05cm2*6.166E-7=175uA/V2.

K'p= Up*Cox= 100cm2*6.166E-7= 62uA/V2.

Lambda(0.6um/1.8um):LAMBDAn=0.158,LAMBDAP=0.023.

Vthn=0.37,Vthp= -0.4935.

I wanted to increase the gain to 100Mhz, can any one help me in this..........

i think there must be some transistors in linear region so that the gain is small.

Re: How to Design a two-stage high-speed op-Amp using equati

Hi
In my opinion, you should start from the gain spec. Your gain is >=70db. let say gain is 80db = 10000

Gain = Gain1* Gain2
Gain1= gm2*Rout1,2 = gm2*ro1*ro2/(ro1 + ro2) = gm2/Id2 *[ VA1*VA2/(VA1 + VA2)]

Gain2= gm6*Rout6,7 = gm6/Id6 * [VA6*VA7/(VA6 + VA7)]

VA = Leff* 1/lambda (Leff = Ldrwn - 2Ld) choose Ldrwn =1um ---> Leff = 1 - 2*0.25=0.5um

From gain equation with knowing gm2 (from GBW), Id2 (from slew rate Id2 = Id5/2) and VA ----> gm6/Id6

We also know gm6/Id6 = 2/Vov6 --->Vov6 --->(W/L)6 buy choosing Id6.
You can do sizing the remaining transistor easy. Good luck

BTW: later you will have phase margin problem because I looked at your equation , you do not mention about it

Re: How to Design a two-stage high-speed op-Amp using equati

afujian said:

i think there must be some transistors in linear region so that the gain is small.

Click to expand...

Hi
Actually,I am doing theoritical calculations based on some equations given in Allen.Hollberg text(book name:CMOS analog design).

He has given some equations relating to W/L or Gm on,how to design a Two-Stage Op-amp.....

So having written the specification,i am calculating to meet the spec.....

Still i have not gone to the actual simulation part...after calculating i charaterize my design using tanner-tool........

I have attached the calculated part with this reply.......

Added after 11 minutes:

doibongvui said:

Hi
In my opinion, you should start from the gain spec. Your gain is >=70db. let say gain is 80db = 10000

Gain = Gain1* Gain2
Gain1= gm2*Rout1,2 = gm2*ro1*ro2/(ro1 + ro2) = gm2/Id2 *[ VA1*VA2/(VA1 + VA2)]

Gain2= gm6*Rout6,7 = gm6/Id6 * [VA6*VA7/(VA6 + VA7)]

VA = Leff* 1/lambda (Leff = Ldrwn - 2Ld) choose Ldrwn =1um ---> Leff = 1 - 2*0.25=0.5um

From gain equation with knowing gm2 (from GBW), Id2 (from slew rate Id2 = Id5/2) and VA ----> gm6/Id6

We also know gm6/Id6 = 2/Vov6 --->Vov6 --->(W/L)6 buy choosing Id6.
You can do sizing the remaining transistor easy. Good luck

BTW: later you will have phase margin problem because I looked at your equation , you do not mention about it

Click to expand...

Thanku very much,I will try with this.......