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Delay and bandwidth calculation for analog signals in Cadence

Hello,

I am working on an analog CMOS circuit. In order to choose the optimum size of the transistors, I want to check the delay and bandwidth for the output signal.

I wanted to sweep the Length and Width of the transistors to find the optimum sizes that are suitable for my project.

To use the calculator for measuring the delay, I should set the Threshold voltage in the following window.

I want to see the amount of delay for all the size sweeping at the same time to compare them.

But the problem is that by changing the size of the transistors, DC level and amplitude of the output signal are varied. So, I could not have all the delayed results at the same time.

My question is that, is there any solution that the threshold value in the calculator set automatically based on the selected signal?

I have another question that would be appreciated if anyone could help me. The calculator has the "bandwidth" option, which I am not sure how to use for calculating the bandwidth of the output signal. (what I did is using ac analysis and then use the calculator to plot the bandwidth which did not plot any result)

Bests

ShawnLogan over 4 years ago

Dear Famaz,

Farnaz said:
But the problem is that by changing the size of the transistors, DC level and amplitude of the output signal are varied. So, I could not have all the delayed results at the same time.
My question is that, is there any solution that the threshold value in the calculator set automatically based on the selected signal?

If you can express the output threshold as the average of the output signal, I would think you could change your numeric constants in the threshold value entries with an expression. In this fashion, the delay will be computed at a threshold dependent on the average output of your amplifier. I assume the average output will change as you change the transistor sizes.

Farnaz said:
The calculator has the "bandwidth" option, which I am not sure how to use for calculating the bandwidth of the output signal. (what I did is using ac analysis and then use the calculator to plot the bandwidth which did not plot any result)

If you examine the function reference for the calculator functions at the On-line support site, the calculator function is designed for a frequency domain signal - not a time domain signal.

https://support.cadence.com/apex/techpubDocViewerPage?xmlName=vivaxlug.xml&title=Virtuoso%20Visualization%20and%20Analysis%20XL%20User%20Guide%20--%20Calculator%20Functions%20-%20Calculator%20Functions&hash=pgfId-1234892&c_version=IC6.1.8&path=vivaxlug/vivaxlugIC6.1.8/appD.html#pgfId-1234892

Shawn
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Farnaz over 4 years ago in reply to ShawnLogan

Thanks for your help
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