jgk2004
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Hello all,
When selecting a technology for a upcoming proposed product, evaluation of the transition frequency, fT is important to see the speed limitations of the technology under test. My questions is, is there a "rule of thumb" when looking at achievable gain bandwidth product (GBW) of a future designed amplifier when considering fT? For example, when I used 90nm, the fT of a min L, 100n, 120mV overdrive transistor had an fT of 60GHz, I thus made the conclusion that fT/10 is easy to achieve for a GBW of an amplifier. My questions, is this a good "rule of thumb"? In my past designs I could always reach this goal before hitting the "power-GBW grave" What I mean by this, is you keep on increasing your current to increase your gm, but at the same time the parasitics keep on building up and thus there isn't an increase in your GBW anymore because Cc increases with parasitics..... GBW = gm/2piCc.... Therefore you keep on digging your grave
What is your idea of this fT ~~GBW relationship??
Jgk
When selecting a technology for a upcoming proposed product, evaluation of the transition frequency, fT is important to see the speed limitations of the technology under test. My questions is, is there a "rule of thumb" when looking at achievable gain bandwidth product (GBW) of a future designed amplifier when considering fT? For example, when I used 90nm, the fT of a min L, 100n, 120mV overdrive transistor had an fT of 60GHz, I thus made the conclusion that fT/10 is easy to achieve for a GBW of an amplifier. My questions, is this a good "rule of thumb"? In my past designs I could always reach this goal before hitting the "power-GBW grave" What I mean by this, is you keep on increasing your current to increase your gm, but at the same time the parasitics keep on building up and thus there isn't an increase in your GBW anymore because Cc increases with parasitics..... GBW = gm/2piCc.... Therefore you keep on digging your grave
What is your idea of this fT ~~GBW relationship??
Jgk
