ECE 3040 Microelectronic Circuits Quiz 4 Solutions, Quizzes of Electrical and Electronics Engineering

Download ECE 3040 Microelectronic Circuits Quiz 4 Solutions and more Quizzes Electrical and Electronics Engineering in PDF only on Docsity! ECE 3040 Microelectronic Circuits Quiz 4 June 9, 2004 Professor Leach Name Instructions. Print your name in the space above. The quiz is closed-book and closed-notes. The quiz consists of 2 problems. Honor Code Statement: I have neither given nor received help on this quiz. Initials 1. The figure shows a Zener diode regulator circuit. It is given that VB = 45V, VZ = 24V, IZ = 5mA, rz = 20Ω, and RL = 12kΩ. (a) In the large signal model of the Zener diode, what is the voltage VZ0? VZ = VZ0 + IZrz =⇒ VZ0 = VZ − IZrz = 23.9V (b) What are the values of IL and I1? IL = VZ RL = 2mA I1 = IZ + IL = 7mA (c) What is the required value of R1? R1 = VB − VZ I1 = 3kΩ (d) Calculate the power dissipated in R1, in the Zener diode, and in RL. PR1 = I 2 1R1 = 147mW PZ = VZIZ = 120mW PRL = I 2 LRL = 48mW (e) If the load current doubles, calculate the decrease in the voltage across the Zener diode. ∆IL = 2mA ∆VZ = −∆IL (rzkR1) = −39.7mV 2. (a) Draw and label a diagram that illustrates the basic construction of the n-channel enhancement- mode MOSFET. (See the notes or book for the diagram.) (b) What must done for an inversion layer to form in the MOSFET, and where is it in the device? Answer: Apply a voltage to the gate which sets up an electric field in the substrate that induces the inversion layer. The inversion layer forms directly below the gate region. (c) What is meant by the threshold voltage of a MOSFET?Answer: The gate-to-source voltage above which drain-to-source current flows. (d) Explain how the phenomenon called pinchoff relates to the current versus voltage characteristic of the MOSFET. Answer: When the device is pinched off, the drain current remains approximately constant as the drain-to-source voltage is increased. 1