How to design an Analog Integrated circuit?

[mvj]

Hi All,

I am very new to the field of analogue IC design and i am wondering how to go about designing a circut( i.e. determine the W and L values of transistors in a circuit) when there is no step by step procedure mentioned in any of the books.For example, some configurations of opamps have a detailed step by step design procedure mentioned in Allan Holberg where as other configurations do not have anything mentioned about the design, how do we desing the circuits in such a case??

Any information is greatly appreciated.

Thank you!!

 

[rakko]

mvj,
I suggest you follow this link to get started. Generally speaking you need to read more than one bokk or paper to do this. You will need cmos layout and rules which you can get from the tool vendor, cmos design principals from any cmos design books. Put the information together yourself and design.
https://www.edaboard.com/threads/62312/

 

[leo_o2]

Use Cadence or Hspice EDA tools for simulation.

 

[mvj]

Thank you Rakko and leo_o2 for the suggestions. Whether it is the layout or simulation, how to decide the W and L values. Should i initially assume some values for the transistor dimensions, simulate them and then based on the result alter them.

Please guide me, thank u!!

 

[hamidmoallemi]

Hi

values of W and L depends on your design and what you want to design,for example if you want to design a logic gate you must consider rise time and fall time of gate and also load capacitance and from formulas choose a initial value and then simulate and change this value to reach to the best value,
about L we usually choose it as small as possible in process,for example for a 180nm process we choose L=180n for most cases
about analog circuits you can refer to "Design of analog CMOS integrated circuits" by Behzad Razavi

 

[mvj]

Hi

from formulas choose a initial value and then simulate and change this value to reach to the best value,

Thank you Hamidmoallemi for you suggestions. I do understand the approach but the problem is that not every circuit topology has formulae mentioned. In most of the cases the functioning of the circuit alone is mentioed and no mathematical analysis is done; in such a case should i do the analysis and derive an equation and use it while designing circuits?

Thank you!!

 

[hamidmoallemi]

hi
To design a circuit especially analog circuit you should analyze some circuits before and have a good sense of circuit design,
in most cases especially in submicron IC design exact formulation is impossible and you must use simulation,but first you should choose some parameters ,
for doing this you must do a rough analysis knowing some formulas such as the voltage swing needed for a transistor ,dc operation point ,...and then go to simulation,