Description
Exercise 9.1
Assume that the subthreshold current of a MOSFET is given by
over the range 0 ≤ VGS ≤ 1 volt and where the factor 2.1 takes into account the effect of interface states. Assume that 106 identical transistors on a chip are all biased at the same
VGS and at VDD = 5 V.
- Calculate the total current that must be supplied to the chip at VGS = 0.5,0.7, and
0.9 V.
- Calculate the total power dissipated in the chip for the same VGS
Exercise 9.2
A silicon MOSFET has parameters Na = 4 × 1016 cm−3,tox = 12 nm = 120 4 × 1010 cm−2, and ϕms = −0.5 V. The transistor is biased at VGS = 1.25 V and VSB = 0. (a) Calculate ∆L for (i) ∆VDS = 1 V, (ii) ∆VDS = 2 V, and (iii) ∆VDS = 4 V.
(b) Determine the minimum channel length L such that ∆L/L = 0.12 for VGS = 1.25 V and ∆VDS = 4 V.
Exercise 9.3
Consider an n-channel silicon MOSFET. The parameters are
10, and VT = 0.35 V. The applied drain-to-source voltage is VDS = 1.5 V.
(a) For VGS = 0.8 V, find ( i ) the ideal drain current, (ii) the drain current if λ =
0.02 V−1, and (iii) the output resistance for λ = 0.02 V−1. (b) Repeat part (a) for VGS = 1.25 V.
Exercise 9.4
- What is subthreshold conduction? Sketch a drain current versus gate voltage plotthat shows the subthreshold current for the transistor biased in the saturation region.
- What is channel length modulation? Sketch an I–V curve that shows the channellength modulation effect.
- What is velocity saturation and what is its effect on the I–V relation of a MOSFET?
- Sketch the space charge region in the channel of a short-channel MOSFET andshow the charge-sharing effect. Why does the threshold voltage decrease in a short-channel NMOS device?
Exercise 9.5
For a uniformly doped n++p+n bipolar transistor in thermal equilibrium,
- sketch the energy-band diagram
- sketch the electric field through the device
- repeat parts (a) and (b) for the transistor biased in the forward-active region.
Exercise 9.6
What is Early effect? How to minimize it?
Exercise 9.7
- From fabrication point of view, why is Si the most commonly used material insemiconductor industry nowadays?
- After this course, what did you learn about semiconductors?
