I have found several interpretations of the sub threshold swing.One is " The subthreshold swing of a device is defined as the change in gate voltage which must be applied in order to create a one decade increase in the output current ".
The other one is that the amount of gate voltage that is needed to bring down the sub threshold current by one decade . which of them is correct and in which context.
Are these two interpretations same but for the former case device is in strong inversion and the latter case the device is in weak inversion ?
What i understood is to have large change in the output current low gate voltage should be enough which implies sub threshold swing should be smaller.If this is true then how are tunneling FETs better over the conventional MOSFETs.(where in tunneling FETs we say the sub threhold swing is not limited?)
Electronic – What does the subthreshold swing of a mosfet actually mean
mosfet
Best Answer
I'll give it a shot. The subthreshold swing definition describes an exponential behavior of the current as a function of voltage. The sign of the parameter should depend on the type of the device (n- or p-), so it's easier to just say that some voltage difference is required for a decade of change in current. Except for the sign it's the same number up or down (if +50mV gives 10 times more current, -50mV should give ten times less). As for the question which device is better... that depends. If you need very low threshold voltages, you don't get a choice, there will be leakage. If you need high operating voltages, then you need thick oxides, which means little leakage and the effect doesn't play much of a role. That used to be the case for most mosfets in the past, but at the current integration density we don't get the next to ideal devices of the past any longer, whether we like that, or not.