Chapter 1

Questions
1. Define the following terms: Atom,Hole, Doping,Electron , Shells, Ionization , PN junction ,
Barrier potential , Reverse bias, Forward bias, Anode, Cathode, Crystal
2. Discuss semiconductors, conductors, and insulators and how they basically differ
3. Discuss covalent bonding in silicon
4. Describe the properties of n-type and p-type semiconductors
5. Describe how current is produced in a semiconductor

Chapter 2

Questions
6. Describe the construction, principle of operation, and analyse the voltage-current (V-I)
characteristic curve of a diode.

Solved Examples
7. Determine the voltage Vo for the network in the figure below

Solution
Initially, it would appear that the applied voltage will turn both diodes “on.” However,
if both were “on,” the 0.7-V drop across the silicon diode would not match the 0.3 V
across the germanium diode as required by the fact that the voltage across parallel elements
must be the same. The resulting action can be explained simply by realizing
that when the supply is turned on it will increase from 0 to 12 V over a period of
time—although probably measurable in milliseconds. At the instant during the rise
that 0.3 V is established across the germanium diode it will turn “on” and maintain
a level of 0.3 V. The silicon diode will never have the opportunity to capture its required
0.7 V and therefore remains in its open-circuit state. The result:

8. Determine the currents I1, I2, and ID2 for the network of the figure below.

Solution
The applied voltage (pressure) is such as to turn both diodes on, as noted by the resulting
current directions in the network of Fig. 2.37. Note the use of the abbreviated
notation for “on” diodes and that the solution is obtained through an application of
techniques applied to dc series—parallel networks.

Applying Kirchhoff’s voltage law around the indicated loop in the clockwise direction yields

9. (a) Sketch the output vo and determine the dc level of the output for the network of the
following figure.
(b) Repeat part (a) if the ideal diode is replaced by a silicon diode.
Solution
(a) In this situation the diode will conduct during the negative part of the input as
shown in Fig. 2.49, and vo will appear as shown in the same figure. For the full
period, the dc level is
Vdc= -0.318Vm= -0.318(20 V) = -6.36 V
The negative sign indicates that the polarity of the output is opposite to the defined polarity

(b) Using a silicon diode, the output has the following appearance

Problems

10. Determine the current I for each of the configurations using the approximate equivalent
model for the diode.

11. Determine Vo and ID for the following networks

(a) If silicon diodes are employed, what is the dc voltage available at the load?
(b) Determine the required PIV rating of each diode.
(c) Find the maximum current through each diode during conduction.
(d) What is the required power rating of each diode?

14. Determine vo and the required PIV rating of each diode for the configuration shown below

Chapter 3

Questions
15. Explain the construction and basic operation of npn BJT transistor.
16. Explain the difference between the structure of an npn and a pnp transistor.
17. Explain common-base, common-collector and common-emitter configurations for pnp BJT
transistor.
18. Explain how a transistor is biased and discuss the transistor currents and their
relationships.
19. Discuss the parameters and characteristics of an npn CE BJT transistor and a pnp CE BJT
transistor.
20. Discuss how a transistor is used as a voltage amplifier.
21. Discuss how a transistor is used as an electronic switch.

Solved Examples
22. Sketch an ideal family of collector curves for the circuit in the following figure for IB = 5 µA
to
25 µA in 5 µ.A increments. Assume βDC = 100 and that VCE doe not exceed breakdown.
 Solution:
Using the relationship Ic = βDC * IB, values of Ic are calculated

The resulting curves are plotted in the figure below

23. (a) For the transistor circuit shown below, what is VCE when V IN = 0 V?
(b) What minimum value of I B is required to saturate this transistor if βDC is 200?
Neglect VCE(sat)
(c) Calculate the maximum value of RB when V IN = 5 V.

Solution:
24. The LED in the following figure requires 30 mA to emit a sufficient level of light. Therefore,
the
collector current should be approximately 30 mA. For the following circuit values,
determine the amplitude of the square wave input voltage necessary to make sure that the
transistor saturates. Use double the minimum value of base current as a safety margin to
ensure saturation. V cc = 9 V, VCE(sat) = 0.3 V, Rc = 270 Ω, RB = 3.3 kΩ, and βDC = 50.

Solution:
Problems
25. A base current of 50 µA is applied to the transistor shown below and a voltage of 5V is

dropped across Rc. Determine the αDC and βDC of the transistor.

26. Determine each current in the following figure. What is the βDC ?

27. Find VCE , VBE , and VCB in both circuits shown below. Determine whether the transistors are
saturated or not.

28. A transistor amplifier has a voltage gain of 50. What is the output voltage when the input
voltage is 100 mV?
29. To achieve an output of 10 V with an input of 300 mV, what voltage gain is required?
30. A 50 mV signal is applied to the base of a properly biased transistor with re’ = 10 and Rc =
560Ω. Determine the signal voltage at the collector.
31. Determine the minimum value of IB required to saturate the transistor in the following
figure if βDC is 125 and VCE(sat) is 0.2 V.

32. Determine IC(sat) for the transistor in the following figure. What is the value of IB necessary to
produce saturation? What minimum value of VIN is necessary for saturation? Assume VCE(Sat) =
0 v.

33. The transistor in the figure below has a βDC of 50. Determine the value of RB required to
ensure saturation when VIN is 5 V. What must VIN be to cut off the transistor? Assume V CE(sat)
= 0 v.

Chapter 4

Questions
34. Explain the difference between field effect transistors (FET) and bipolar junction transistors
(BJT).
35. Explain why BJTs are bipolar devices while FETs are unipolar devices.
36. Explain why BJTs are current controlled devices while FETs are voltage controlled devices.
37. Explain why FETs are called “field effect”.
38. Compare the input impedance of BJTs, JFET and MOSFET.
39. Which type of transistors (BJTs or FETs) are particularly useful in integrated circuit chips
and why?
40. Discuss the construction and principle of operation of n-channel JFET and p-channel JFET.
41. Why must the gate-to-source voltage of an n-channel JFET always be either 0 or negative?
42. Explain ohmic area, constant-current area, and breakdown for an n-channel JFET transistor.
Verify that ID does not drop off at pinch-off and maintains the saturation level.
43. Define pinch-off voltage and cut-off voltage.
44. Describe in your own words why IG is effectively zero amperes for a JFET transistor.
45. Explain the construction and principle of operation characteristic of n-channel depletion
type MOSFET, p-channel depletion type MOSFET, n-channel enhancement type MOSFET
and p-channel enhancement type MOSFET.
46. Explain the structural difference between D-MOSFET and E-NMOSFET

Solved Examples
47. The partial data sheet for an n-channel JFET indicates that typically lDss = 9 mA and VGS(off) = -
8 V (maximum). Using these values, determine the drain current for VGS = 0V, -1 V and -4 V.
Solution:

48. For a certain D-MOSFET, lDSS = 10 mA and VGS(off) = -8 V.

49. The partial data sheet for a p-channel E-MOSFET indicates that typically lD(on) = 500 mA
(minimum) and VGS= 10 V and VGS(th) = 1 V. Determine the drain current for VGS = 5V.
Solution:

First solve for K:

Problems
50. A JFET has a specified pinch-off voltage of 5 V. When VGS = 0, what is VDS at the point where
the drain current becomes constant?
51. A certain n-channel JFET is biased such that VGS = -2 V. What is the value of VGS(off) if Vp is
specified to be 6 V? Is the device on?
52. A certain JFET data sheet gives VGS(off) = -8 V and lDSS = 10 mA. When VGS = 0, what is lD
for values of DS above pinch-off? VDD = 15 V.
53. For a certain D-MOSFET, lDSS =18 mA and VGS(off) = +10 V.
(a) Is this an n-channel or a p-channel?
(b) Calculate ID at VGS = +3 v.
(c) ) Calculate ID at VGS = -3 v.
54. The data sheet for an E-MOSFET gives lD(on) = 100 mA (minimum) and VGS= 8 V and VGS(th) = 4
V. Find ID when VGS = 6V.
Summary of Field Effect Transistors