An NMOS transistor has a threshold voltage (Vt0) of 0.4V and a supply voltage of 1.2V. There is a proposal to lower the Vt0 by 100mV to improve transistor speed.

a. By what factor would the sub-threshold leakage increase at room temperature with Vgs = 0V. Assume n=1.5 and ɳ=0.04.

b. By what factor would the sub-threshold leakage increase at 85C. Assume Vt0 remains constant with temperature.

c. Does Vt0 remain constant with temperature? What does Vt0 really do with an increase in temperature? Does this make the sub-threshold increase with temperature better or worse?