What is the best practice of optimize both CMRR PSRR and DC Gain of an amplifier?

Dear SimbaG,

SimbaG said:

Could you give me some suggestions to optimizing all performance of this amplifier? 

The design optimization process for any circuit design depends on your design requirements. Some requirements are more important than others to a design and hence one chooses design parameters that maximize performance relative to the most important or critical design requirements. There are many papers, texts, and references available that cover the trade-offs between the parameters you are computing (such as gain, bandwidth, PSSR, CMRR).

In many cases, a manual optimization is performed as one knows the trade-offs between parameters. However, ADE Assembler does have a circuit optimizer if you are interested. It is very important, however, that you understand the trade-offs between the parameters you are modifying to optimize your design. I would recommend reading some texts or papers regarding these parameters before relying totally on a circuit optimizer. A few documents exist within the On-lien support portal:

Real-time tuning using ADE-Explorer:

https://support.cadence.com/apex/techpubDocViewerPage?xmlName=explorer.xml&title=Virtuoso%20ADE%20Explorer%20User%20Guide%20--%20Real-Time%20Tuning%20in%20Simulations%20-%20Opening%20the%20Real-Time%20Tuning%20Assistant&hash=pgfId-1016466&c_version=ICADVM20.1&path=Explorer/ExplorerICADVM20.1/chap10.html#pgfId-1016466

Manual tuning using ADE Assembler:

support.cadence.com/.../techpubDocViewerPage

ADE Assembler also ha a Rapid Adoption Kit (RAK) describing its circuit optimizer at the On-lIne support URL:

https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1Od000000050Y8EAI&pageName=ArticleContent

I hope this helps.

Shawn

Dear SimbaG,

SimbaG said:

Could you give me some suggestions to optimizing all performance of this amplifier? 

The design optimization process for any circuit design depends on your design requirements. Some requirements are more important than others to a design and hence one chooses design parameters that maximize performance relative to the most important or critical design requirements. There are many papers, texts, and references available that cover the trade-offs between the parameters you are computing (such as gain, bandwidth, PSSR, CMRR).

In many cases, a manual optimization is performed as one knows the trade-offs between parameters. However, ADE Assembler does have a circuit optimizer if you are interested. It is very important, however, that you understand the trade-offs between the parameters you are modifying to optimize your design. I would recommend reading some texts or papers regarding these parameters before relying totally on a circuit optimizer. A few documents exist within the On-lien support portal:

Real-time tuning using ADE-Explorer:

https://support.cadence.com/apex/techpubDocViewerPage?xmlName=explorer.xml&title=Virtuoso%20ADE%20Explorer%20User%20Guide%20--%20Real-Time%20Tuning%20in%20Simulations%20-%20Opening%20the%20Real-Time%20Tuning%20Assistant&hash=pgfId-1016466&c_version=ICADVM20.1&path=Explorer/ExplorerICADVM20.1/chap10.html#pgfId-1016466

Manual tuning using ADE Assembler:

support.cadence.com/.../techpubDocViewerPage

ADE Assembler also ha a Rapid Adoption Kit (RAK) describing its circuit optimizer at the On-lIne support URL:

https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1Od000000050Y8EAI&pageName=ArticleContent

I hope this helps.

Shawn

Thank you for your reply.

First of all, sorry to say that I can't access the documents you provide, I am emailing my university help desk to ask if they can help me. After that, I will open the documents.

University users cannot self-register. Please contact your University Program Representative or Customer Support for registration assistance.

Moreover, as you said, manual optimization is important, and there are many trade-offs. But what I interesting in this thread is using Cadence Optimization to assist me in tuning my opamp, and how to use Cadence ADE.

An optimization includes DC Gain, GBW and MOSFET region via Virtuoso ADE had been completed as my screenshots show. 

My question actually is mainly focused on, how to add CMRR condition into Virtuoso ADE optimization? Such as CMRR > xx dB.

For an example, the DC Gain > 60dB condition is "value(dB20(VF("/vout")) 2) and max 60. This means DC Gain > 60dB in cadence ADE.

Dear SimbaG,

SimbaG said:

First of all, sorry to say that I can't access the documents you provide, I am emailing my university help desk to ask if they can help me. After that, I will open the documents.

I would highly recommend you follow through with your university as it it sounds you need some good reference material on the Cadence tools.

SimbaG said:

My question actually is mainly focused on, how to add CMRR condition into Virtuoso ADE optimization? Such as CMRR > xx dB

You will create an waveform for the CMRR function and set specifications for its minimum value at the specific frequencies required for your specification. Essentially, the value() function using the CMRR function as one argument and a specific frequency will provide the value of the CMRR function at a specific frequency to compare with the requirement at that specific frequency.

The resulting value will be a parameter used in the optimization process.

Shawn

Unknown said:

I would highly recommend you follow through with your university as it it sounds you need some good reference material on the Cadence tools.

Yes, thanks again for your suggestion.

Unknown said:

Essentially, the value() function using the CMRR function as one argument and a specific frequency will provide the value of the CMRR function at a specific frequency to compare with the requirement at that specific frequency.

Yes, CMRR is a function of frequency, so the condition should be like value( CMRR(VF("/vout")) 2), to get CMRR@2Hz.

Of course, there is no function named as CMRR. In my practice, I have to change the testbench to calculate CMRR, so that I can't add DC Gain condition in CMRR testbench.

Should I copy the opamp and use two instances of the opamp, one with Gain testbench, another with CMRR testbench? Is it a good practice?

Dear Simba,

SimbaG said:

In my practice, I have to change the testbench to calculate CMRR, so that I can't add DC Gain condition in CMRR testbench.

Should I copy the opamp and use two instances of the opamp, one with Gain testbench, another with CMRR testbench? Is it a good practice?

You can use a single test bench and run different analyses with a single testbench. If you want to use the same test bench with different analyses and you need to reconfigure it for different tests, you may be able to use the analogLib switch and relay components. Information can be found on the On-line support site or from your UNIX promot:

spectre -h relay

spectre -h switch

Shawn

Thanks a lot.

I am going to look up how to analyze CMRR and DC Gain in one test bench with two analyses. And also appreciate your patience.

Have a nice day.