Question

If a circuit designer wants to ensure that a MOSFET exhibits no more than 5 pA of leakage current in the OFF state, and also wants a 0.4V threshold voltage (the Vr is defined as the Vgs at which lds O.15 HA). What is the maximum subthreshold swing the device can possess? (3pts) RS

Answer 1

leakage current in OFF state of a MOSFET= 5pA

Threshold voltage V_T = 0.4 volts

I_ds = 0.15microamp

Sub threshold swing of MOSFET is defined as the change required in gate voltage in order to cause 1 decade change in drain to source current (output current).

First we have to find out slope od log I_ds vs V_gs characteristics .

maximum sub threshold swing = 1/slope

slope= log (leakage current + drain to source current at threshold voltage ) / threshold voltage

=

log(5pA+0.154A)]/0.4volts log(0.000005/A+0.4uA)/0.4v-15.99decade/volts

Hence maximum sub threshold swing = 1/ Slope = -0.063 volts/decade