MOSFET biasing effect on internal resistances & capacitances

Q.  What is the effect of MOSFET biasing in the saturation region especially while representing the internal resistances and capacitances in n-channel E-MOSFET configuration?
- Published on 24 Sep 15

a. Channel gets pinched off at the drain by increasing the value of Cgd
b. Channel gets pinched off at the source by increasing the value of Cgd
c. Channel gets pinched off at the drain by decreasing the value of Cgd upto zero
d. Channel gets pinched off at the source by decreasing the value of Cgd

ANSWER: Channel gets pinched off at the drain by decreasing the value of Cgd upto zero
 

    Discussion

  • Satyawati Patil   -Posted on 07 Oct 15
    In E-MOSFET, the internal capacitances also include gate to source capacitance and gate to drain capacitance. The values of these two capacitances are approximately equal especially in the non-saturation region.

    When E-MOSFET is biased in the saturation region,the channel is pinched off at the drain terminal. Due to this, the value of gate to drain capacitance gets reduced to zero.

    However,the value of gate to source capacitance undergoes variations due to change in the size of device. Other internal capacitances include the parasitic capacitances, which generally occurs due to overlapping of oxide layer on the source and drain contacts.

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