ELECTRONICS ENGINEERING EC 101 UNIT 3 (JFET AND MOSFET) LONG QUESTIONS (10 MARKS) 1. Draw the construction diagram and explain the working of P-Channel JFET. Also draw the characteristics curve and transfer characteristics. 2. Sketch the structure of P-Channel Depletion Type MOSFET and explain its principle of operation with neat diagram. Also sketch its V-I Characteristics and circuit symbols for it. 3. Describe the construction and operation of a MOSFET in Enhancement mode. Draw its characteristics and equivalent circuit of the device. 4. Draw and explain the Voltage Divider Bias Configuration of JFET. 5. Determine V GS, I D, V DS, V D, V G and V s for the circuit shown in Fig 1. Fig.:1 6. Draw the structure of an n-channel JFET and explain it s principle of operation. Also draw it s drain and transfer characteristics with the help of suitable circuit. 7. Determine the following: (i) I DQ (ii)v gsq (iii) V D (iv) V S (v) V DS (for Fig.:2) Page 1
Fig.:2 8. Explain construction and working of CMOS. 9. What is the significance of the threshold voltage V T in: (i) Depletion mode, (ii) Enhancement mode MOSFET. 10. Determine the following: (i) I DQ (ii)v gsq (iii) V D (iv) V S (v) V DS (vi)v DG (for Fig.:3) Fig.:3 Page 2
MEDIUM QUESTION (5 MARKS) 1. How an FET can be used as a voltage controlled resistor? 2. What is the major difference between a bipolar and an unipolar device? Explain with example. 3. Explain the difference between JFET and MOSFET. 4. The pinch-off voltage of a p-channel JFET is V p = 5V and the drain-to-source current I DSS = -40mA. The vaolue of drain to source Voltage V DS is such that the transistor is operating in the saturated region, the drain current I D = -15mA. Determine the gate to source voltage V GS.. 5. Explain transistor as a switch. 6. For the common source FET amplifier with source resistance R S, derive the expression for voltage gain, input impedance and output impedance. (Fig.:4) Fig.:4 7. Explain Source Follower Configuration with the help of Suitable Circuit Diagram. Also give the various features of this configuration. 8. Can a depletion type MOSFET operate in Enhancement Mode? If yes, why and how, if no, Why? 9. Draw a small signal equivalent circuit of JFET amplifier in Common Source Configuration and Show that the voltage gain is A v =. where µis the amplification factor and r d is the drain resistance. 10. An n-channel having V p =-4V and I DSS = 10mA is used in the circuit of fig.: 5 Determine I D and V DS. Page 3
Fig.:5 11. Explain CMOS as an Inverter SMALL QUESTION (2 MARKS) 1) What are the advantages of FET over BJT? 2) Write the constructional difference between Depletion type and enhancement type MOSFET. 3) Explain pinch of voltage of FET. 4) Define drain resistance of FET. 5) Define Transconductance of FET. 6) Define amplification factor of FET. 7) Define Drain to source saturation current of JFET. 8) Write Shockley s Equation. 9) Why MOSFET is also called IGFET. 10) What are the effects of SiO 2 layer in MOSFET. 11) What is meant by Gate to Source Threshold Voltage in E-MOSFET. 12) Write down the application of JFET. 13) Sketch circuit symbols for a P-Channel Depletion Type MOSFET. 14) Sketch circuit symbols for a N-Channel Depletion Type MOSFET. 15) What is the need for biasing a transistor. 16) State the various configuration of JFET amplifier. Also draw the approximate AC equivalent Circuit. 17) Which one of the following has the highest input resistance (i) n-channel JFET (ii) P-channel MOSFET. Page 4
18) Which factors make the JFET superior to BJT. 19) Give the Classification of FET. 20) What is the significance of field effect in JFET. 21) Why the thickness of depletion layer is more towards the drain and less towards the source. 22) State the application of MOSFET. Page 5