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Analog Design Procedure

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navi_s

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Hello All,
I have some general question about designing some Analog block and steps.
Lets consider we want to design simple Current Source biased by simple PMOS current source with given GAIN, GBW, CL
1. First should be from given GBW and load capacitance obtain the Gm
2. Then we from given Amplification(GAIN) and from Gm of step 1 we should decide what should be output resistance in order to achieve desired gain.
3. What next. Based on Gm and Rout we should obtain Current. Is that right?
4. We want some DC output level. How with all these parameters to design PMOS current source transistor and aplification NMOS such that to have proper DC, Output current, Gm and Rout??

Thank you in advance
 

I think the key rather is the iteration, not step by step design. From your method it is missing that what is happening when it turns out that achievable gain is too small, it is not linear enough or its flicker noise is huge? In many cases we have to change the circuit itself after a step, not its parameters and we cannot add these as steps to your basic calculation.

Browse for "analog octagon", I think that is a true method.

And if you have no experience it is recommended to start with minimum sizes in your amplifier example, and increase sizes until all parameters are good enough or to see what is achievable with such a circuit, and just keep that in your mind.

For general, bit more complicated cases there are some step by step design methods, if you want to see some check this: https://aicdesign.org/2016-short-course-notes-2/
 

    navi_s

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