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Design >> Analog Design >> Max AC operating voltage VS. AMR
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Message started by rfmems on Apr 26^th, 2010, 1:10am

Title: Max AC operating voltage VS. AMR
Post by rfmems on Apr 26^th, 2010, 1:10am

In design rule manuals, foundries normally give a AMR (absolute maximum rating), which is a hard limit for maximum AC operating voltage. But also warn that even below the AMR value (above VDDmax), there still is degradation.

I am wondering, what kind of rule should apply on the max AC operating voltage. Below AMR for sure, but how high can it go without degrading the performance.

Title: Re: Max AC operating voltage VS. AMR
Post by vivkr on Apr 27^th, 2010, 1:28am

Usually, the AMR is defined as the point where the performance of the transistor degrades by a certain amount, e.g. the leakage increases beyond a certain amount, or the threshold changes by so much amount.
What this also means is that there will likely be some performance degradation even before you reach AMR. At AMR, you simply cross a certain threshold. So there is some measure of arbitrariness in this definition, as in every definition of parameter limits.

The design manual usually specifies in quite some detail as to how the measurement was done, and how AMR is defined. You should check this out.

In some cases, the AMR may really be defined as the point at which the device suffers catastrophic breakdown although I doubt if many foundries define AMR on this basis. In this case, you would of course be seeing substantial performance degradation way before onset of breakdown, i.e. way before you reach AMR.

Vivek