25896_Electronics Notes Final

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Transcript of 25896_Electronics Notes Final

Chas Keithan Electronics Notes Chapter 1 1) An ideal voltage source has zero internal resistance. 2) A real voltage source has a small internal resistance. 3) If a load resistance is 100 , a stiff voltage source has a resistance of less than 1 . 4) An ideal current source has infinite internal resistance. 5) A real current source has a large internal resistance. 6) If a load resistance is 100 , a stiff current source has a resistance of more than 10 k. 7) The Thevenin voltage is the same as the open-load voltage. 8) The Thevenin resistance is equal in value to the internal resistance of a Norton circuit. 9) To get the Thevenin voltage, you have to open the load resistor. 10) To get the Norton current, you have to short the load resistor. 11) The Norton current is sometimes called the shorted-load current. 12) A solder bridge may produce a short. 13) A cold-solder joint usually produces an open. 14) An open resistor has zero current through it. 15) A shorted resistor has zero voltage across it. 16) An ideal voltage source and an internal resistance are examples of the second approximation. 17) Treating a connecting wire as a conductor with zero resistance is an example of the ideal approximation. 18) The voltage out of an ideal voltage source is constant. 19) The current out of an ideal current source is constant. 20) Thevenins theorem replaces a complicated circuit facing a load by an ideal voltage source and series resistor. 21) Nortons theorem replaces a complicated circuit facing a load by an ideal current source and parallel resistor. 22) One way to short a device is with a solder bridge. 23) Derivations are produced by mathematics. Chapter 2 1) The nucleus of a copper atom contains how many protons? 29.

2) The net charge of a neutral copper atom is 0. 3) Assume the valence electron is removed from a copper atom. The net charge of the atom becomes + 1. 4) The valence electron of a copper atom experiences what kind of attraction toward the nucleus? Weak. 5) How many valence electrons does a silicon atom have? 4. 6) Which is the most widely used semiconductor? Silicon. 7) How many protons does the nucleus of a silicon atom contain? 14. 8) Silicon atoms combine into an orderly pattern called a crystal. 9) An intrinsic semiconductor has some holes in it at room temperature. What causes these holes? Thermal energy. 10) When an electron is moved to a higher orbit level, its energy level with respect to the nucleus increases. 11) The merging of a free electron and a hole is called recombination. 12) At room temperature an intrinsic silicon crystal acts approximately like an insulator. 13) The amount of time between the creation of a hole and its disappearance is called lifetime. 14) The valence electron of a conductor can also be called a free electron. 15) A conductor has how many types of flow? 1. 16) A semiconductor has how many types of flow? 2. 17) When a voltage is applied to a semiconductor, holes will flow none of the above. 18) For semiconductor material, its valence orbit is saturated when it contains 8 electrons. 19) In an intrinsic semiconductor, the number of holes equals the number of free electrons. 20) Absolute zero temperature equals -273C. 21) At absolute zero temperature an intrinsic semiconductor has no holes or free electrons. 22) At room temperature an intrinsic semiconductor has a few free electrons and holes. 23) The number of free electrons and holes in an intrinsic semiconductor decreases when the temperature decreases. 24) The flow of valence electrons to the right means that holes are flowing to the left. 25) Holes act like positive charges. 26) Trivalent atoms have how many valence electrons? 3. 27) An acceptor atom has how many valence electrons? 3. 28) If you wanted to produce an n-type semiconductor, which of these would you use? Donor atoms. 29) Electrons are the minority carriers in which type of semiconductor? P-type.

30) How many free electrons does a p-type semiconductor contain? Only those produced by thermal energy. 31) Silver is the best conductor. How many valence electrons do you think it has? 1. 32) Suppose an intrinsic semiconductor has 1 billion free electrons at room temperature. If the temperature drops to 0C, how many holes are there? Fewer than 1 billion. 33) An external voltage source is applied to a p-type semiconductor. If the left end of the crystal is positive, which way dot the majority carriers flow? Right. 34) Which of the following doesnt fit in the group? Conductor. 35) Which of the following is approximately equal t room temperature? 25C. 36) How many electrons are there in the valence orbit of a silicon atom within a crystal? 8. 37) Negative ions are atoms that have gained an electron. 38) Which of the following describes an n-type semiconductor? Neutral. 39) A p-type semiconductor contains holes and negative ions. 40) Which of the following describes a p-type semiconductor? Neutral. 41) As compared to a germanium diode, a silicon diodes reverse saturation current is lower. 42) What causes the depletion layer? Recombination. 43) What is the barrier potential of a silicon diode at room temperature? .7V. 44) When comparing the energy gap of germanium and silicon atoms, a silicon atoms energy gap is higher. 45) In a silicon diode the reverse current is usually very small. 46) While maintaining a constant temperature, a silicon diode has its reverse-bias voltage increased. The diodes saturation current will remain the same. 47) The voltage where avalanche occurs is called the breakdown voltage. 48) The energy hill of diodes pn junction will decrease when the diode is forward biased. 49) When the reverse voltage decreases from 10 to 5 V, the depletion layer becomes smaller. 50) When a diode is forward-biased, the recombination of electrons and holes may produce heat, light and radiation. 51) A reverse voltage of 10 V is across a diode. What is the voltage across the depletion layer? 10 V. 52) The energy gap in a silicon atom is the distance between the valence band and the conduction band. 53) The reverse saturation current doubles when the junction temperature increases 10C. 54) The surface-leakage current doubles when the reverse voltage increases 100%. Chapter 3 1) When the graph of current versus voltage is a straight line, the device is referred to as linear.

2) What kind of device is a resistor? Linear. 3) What kind of device is a diode? Nonlinear. 4) How is a non-conducting diode biased? Reverse. 5) When the diode current is large, the bias is forward. 6) The knee voltage of a diode is approximately equal to the barrier potential. 7) The reverse current consists of minority-carrier current and surface-leakage current. 8) How much voltage is there across the second approximation of a silicon diode when it is forward biased? .7 V. 9) How much current is there through the second approximation of a silicon diode when it is reverse biased? 0. 10) How much forward diode voltage is there with the ideal-diode approximation? 0. 11) The bulk resistance of a 1N4001 is .23 . 12) If the bulk resistance is zero, the graph above the knee becomes vertical. 13) The ideal diode is usually adequate when troubleshooting. 14) The second approximation works well when troubleshooting, load resistance is high, and/or source voltage is high. 15) The only time you have to use the third approximation is when load resistance is low. Chapter 4 1) If N1 / N2 = 4, and the primary voltage is 120 V, what is the secondary voltage? 30 V. 2) In a step-down transformer, which is larger? Primary voltage. 3) A transformer has a turns ratio of 2:1. What is the peak secondary voltage if 115 V rms is applied to the primary winding? 81.3 V. 4) With a half-wave rectified voltage across the load resistor, load current flows for what part of a cycle? 180. 5) Suppose line voltage may be as low as 105 V rms or as high as 125 V rms in a half-wave rectifier. With a 5:1 step-down transformer, the minimum peak load voltage is closest to 29.7 V. 6) The voltage out of a bridge rectifier is a full-wave signal. 7) If the line voltage is 115 V rms, a turns ratio of 5:1 means the rms secondary voltage is closest to 23 V. 8) What is the peak load voltage in a full-wave rectifier if the secondary voltage is 20 V rms? 14.1 V. 9) We want a peak load voltage of 40 V out of a bridge rectifier. What is the approximate rms value of secondary voltage? 28.3 V. 10) With a full-wave rectified voltage across the load resistor, load current flows for what part of a cycle? 360.

11) What is the peak load voltage out of a bridge rectifier for a secondary voltage of 12.6 V rms? (Use second approximation.) 16.4 V. 12) If line frequency is 60 Hz, the output frequency of a half-wave rectifier is 60 Hz. 13) If line frequency is 60 Hz, the output frequency of a bridge rectifier is 120 Hz. 14) With the same secondary voltage and filter, which has the most ripple? Half-wave rectifier. 15) With the same secondary voltage and filter, which produces the least load voltage? Full-wave rectifier. 16) If the filtered load current is 10 mA, which of the following has a diode current of 10 mA? Half-wave rectifier. 17) If the load current is 5 mA and the filter capacitance is 1000 F, what is the peak -to-peak ripple out of a bridge rectifier? 41.7 mV. 18) The diodes in a bridge rectifier each have a maximum dc current rating of 2 A. This means the dc load current can have a maximum value of 4 A. 19) What is the PIV across each diode of a bridge rectifier with a secondary voltage of 20 V rms? 28.3 V. 20) If the secondary voltage increases in a bridge rectifier with a capacitor-input filter, the load voltage will increase. 21) If the filter capacitance is increased, the ripple will decrease. 22) A circuit that removes positive or negative parts of a waveform is called a clipper. 23) A circuit that adds a positive or negative dc voltage to an input sine-wave is called a clamper. 24) For a clamper circuit to op