vvchan said:Is there any defination or approximation when can I consider a MOS as a long channel one?
elmolla said:The long channel devices (usually used in MOSFETs) are the good old devices with no short channel effects, strictly speaking, there is no geometrical threshold for which we can define the long channel devices, but speaking withing a given range of operation voltage we can speak for a given range of channel length to be a long channel devices.
eg. 10µm channel devices can be dealt with most of the time as long channel devices
Strictly speaking, short channel devices are devices that exhibit one of the following characteristics:
1. Drain Induced Barrier Lowering (DIBL).
2. Linear Variation of saturation current after pinch-off (Pinch off before velocity saturation).
3. The Channel Lenght Modulation is very apparent.
4. The Mobility Degradation is very apparant.
A long channel device is a device that doesn't exhibit ANY of these effects. So the only way you can check on it is to check the C/Cs of the device you're working with in the operation region you're working at and see if these C/Cs are there.