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Homework Questions

1. The term 'Saturation' has a different meaning in the  I-V characteristics of  MOSFET and  BJT. Explain the difference between BJT and  MOSFET.

2. In MOSFET,  carriers need to move from  Source to Drain via the inversion channel under certain Vgs and Vds conditions. A "Pinched off" channel takes place at the drain side. Now explain how the carriers move in the Pinched off region of the channel (that is, the depleted portion of channel, near the drain end)  ?  In other words, if the channel is pinched off, then there are 'negligible' amounts of carriers there.  How can it conduct electric currnets ?

3. In a MOSFET, if one increases |Vds| in the saturation region, the Id will  remain at a near constant-value. However, if the|Vds| is increased much further, then MOSFET will run away (i.e., breakdown), and the |Id| will be  increased rapidly. Explain what causes the device to run away in terms of physical phenomena in the drain, source, channel and oxide under this  |Vds| condition. ?