EE 3401 Electronics Homework #4

Read Chapter 3.

Section 3.1 MOSFET

Problem 3.1

a) Calculate the drain current in an NMOS transistor with parameters VTN = 0.4 V, kn’ =

120 µA/V2, W = 10 µm, L = 0.8 µm, and with applied voltages of VDS = 0.1 V and

(i) VGS = 0 V

(ii) VGS = 1 V

b) Repeat part (a) for VDS = 4 V.

Problem 3.3 The transistor characteristics iD versus VDS for an NMOS device are shown in

Figure P3.3.

a) Is this an enhancement-mode or depletion-mode device?

Problem 3.4 For an n-channel depletion-mode MOSFET, the parameters are VTN = -2.5 V and Kn

= 1.1 mA/V2.

a) Determine ID for VGS = 0; and

(i) VDS = 0.5 V

(ii) VDS = 2.5 V

(iii) VDS = 5 V

b) Repeat part (a) for VGS = 2 V.

Problem 3.5 The threshold voltage of each transistor in Figure P3.5 is VTN = 0.4 V. Determine

the region of operation of the transistor in each circuit.

Problem 3.6 The threshold voltage of each transistor in Figure P3.6 is VTP = -0.4 V. Determine

the region of operation of the transistor in each circuit.

Problem 3.9 An n-channel enhancement-mode MOSFET has parameters VTN = 0.4 V, W = 20

µm, L = 0.8 µm, tox = 200x10-8 cm, µn = 650 cm2/V, and oxide permittivity of 3.9 x 3.38 x 10-14

F/cm.

a) Calculate the conduction parameter Kn

b) Determine the drain current when VGS = VDS = 2 V

c) With VGS = 2 V, what value of VDS puts the device at the edge of saturation?

Problem 3.17 Calculate the drain current in a PMOS transistor with parameters VTP = -0.5 V, kp’

= 50 µA/V2, W = 12 µm, L = 0.8 µm, and with applied voltages of VSG = 2 V and

(i) VSD = 0.2 V

(ii) VSD = 0.8 V

(iii) VSD = 1.2 V

(iv) VSD = 2.2 V

(v) VSD = 3.2 V

Problem 3.20 For an NMOS enhancement-mode transistor, the parameters are: VTN = 1.2 V, Kn

= 0.2 mA//V2, and λ = 0.01 V-1. Calculate the output resistance ro for VGS = 2.0 V and for VGS =

4.0 V. What is the value of VA?

Section 3.2 Transistor DC analysis

Problem 3.26 In the circuit in Figure P3.26, the transistor parameters are VTN = 0.8 V and Kn =

0.5 mA/V2. Calculate VGS, ID, and VDS.

Problem 3.30 Consider the circuit in Figure P3.30. The transistor parameters are VTP = - 0.8 V

and Kp = 0.5 mA/V2. Determine ID, VSG, and VSD.

Problem 3.31 For the circuit in Figure P3.31, the transistor parameters are VTP = - 0.8 V and Kp =

200 µA/V2. Determine VS and VSD.

Problem 3.34 The transistor parameters for the transistor in Figure P3.34 are VTN = 0.4 V, kn’ =

120 µA/V2, and W/L = 50.

a) Determine VGS such that ID = 0.35 mA

b) Determine VDS and VDS(sat)

Problem 3.37 The parameters of the transistors in Figures P3.37

(a) and (b) are Kn = 0.5 mA/V2, VTN = 1.2 V, and λ = 0.

Determine VGS and VDS for each transistor when

(i) IQ = 50 µA

(ii) IQ = 1 mA

Problem 3.38 For the circuit in Figure P3.38, the transistor parameters are VTN = 0.6 V and Kn =

200 µA/V2. Determine VS and VD.

Section 3.3 MOSFET Switch and Amplifier

Problem 3.50 Consider the circuit in Figure P3.50. The circuit parameters are VDD = 3 V and RD

= 30 kΩ. The transistor parameters are VTN = 0.4 V and kn’ = 120 µA/V2.

a) Determine the transistor width-to-length ratio such that VO = 0.08 V when VI = 2.6 V

b) Repeat part a) for VI = 3 V.