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Unit 1: PN Junction - Practice Quiz

ECE226 — Analog Electronic Devices And Circuits 60 Questions
0 Correct 0 Wrong 60 Left
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1 The depletion region in a PN junction is a region that is depleted of:

Depletion region Easy
A. Covalent bonds
B. Mobile charge carriers
C. Fixed negative ions
D. Fixed positive ions

2 The width of the depletion region in a PN junction increases when the junction is:

Depletion region Easy
A. Left unbiased and heated
B. Reverse biased
C. Doped more heavily
D. Forward biased

3 The junction capacitance that dominates when a diode is reverse biased is called:

Junction capacitance Easy
A. Coupling capacitance
B. Transition capacitance
C. Storage capacitance
D. Diffusion capacitance

4 The diffusion capacitance of a PN junction is significant when the diode is:

Junction capacitance Easy
A. Forward biased
B. Reverse biased
C. In breakdown region
D. At zero bias only

5 In the diode equation , the term represents the:

Diode equation Easy
A. Peak forward current
B. Junction leakage voltage
C. Reverse saturation current
D. Breakdown current

6 In the diode equation, the thermal voltage at room temperature is approximately:

Diode equation Easy
A.
B.
C.
D.

7 The reverse saturation current of a diode approximately:

Effect of temperature on reverse saturation current Easy
A. Doubles for every rise in temperature
B. Falls to zero at high temperature
C. Remains constant with temperature
D. Halves for every rise

8 The reverse saturation current increases with temperature mainly because of increased:

Effect of temperature on reverse saturation current Easy
A. Barrier potential
B. Generation of minority carriers
C. Doping concentration
D. Width of the depletion region

9 A PN junction diode is formed by joining:

Construction and Working Easy
A. Two P-type semiconductors
B. A P-type and an N-type semiconductor
C. A metal and an insulator
D. Two N-type semiconductors

10 A silicon PN junction diode starts conducting appreciably in forward bias at about:

Construction and Working Easy
A.
B.
C.
D.

11 In the forward V-I characteristic of a diode, the current:

V-I characteristics Easy
A. Decreases as voltage increases
B. Remains zero at all voltages
C. Is constant at all voltages
D. Rises rapidly after the knee voltage

12 In the reverse bias region of a diode's V-I characteristic, the current is:

V-I characteristics Easy
A. Exactly zero always
B. Very large and increasing
C. Very small and nearly constant
D. Equal to the forward current

13 The main function of a rectifier is to convert:

Junction diode rectifiers Easy
A. DC into AC
B. Low voltage into high voltage
C. AC into DC
D. AC into higher-frequency AC

14 A rectifier circuit works by exploiting the diode's property of:

Junction diode rectifiers Easy
A. Conducting in only one direction
B. Amplifying signals
C. Generating AC voltage
D. Storing charge indefinitely

15 A half-wave rectifier conducts during:

Half wave rectifiers Easy
A. Only the negative half cycle continuously
B. Both half cycles of the AC input
C. Only one half cycle of the AC input
D. None of the AC cycle

16 The ripple frequency at the output of a half-wave rectifier fed by a supply is:

Half wave rectifiers Easy
A.
B.
C.
D.

17 The minimum number of diodes required in a bridge full-wave rectifier is:

Full wave rectifiers Easy
A. Three
B. One
C. Two
D. Four

18 The ripple frequency at the output of a full-wave rectifier fed by a supply is:

Full wave rectifiers Easy
A.
B.
C.
D.

19 The maximum theoretical efficiency of a half-wave rectifier is approximately:

Efficiency Easy
A.
B.
C.
D.

20 A Zener diode is normally operated in the:

Zener diode Easy
A. Cut-off region
B. Reverse breakdown region
C. Saturation region
D. Forward conduction region

21 In an unbiased PN junction, the width of the depletion region on the lightly doped side compared to the heavily doped side is:

Depletion region Medium
A. Larger on the heavily doped side
B. Equal on both sides
C. Zero on the lightly doped side
D. Larger on the lightly doped side

22 When forward bias is applied to a PN junction, the depletion region width:

Depletion region Medium
A. Remains constant
B. Becomes infinite
C. Decreases
D. Increases

23 The transition (depletion) capacitance of a reverse-biased PN junction varies with reverse voltage approximately as:

Junction capacitance Medium
A.
B.
C.
D.

24 Diffusion capacitance in a PN junction becomes dominant under which condition?

Junction capacitance Medium
A. Breakdown region
B. Reverse bias
C. Zero bias only
D. Forward bias

25 According to the Shockley diode equation , for a large reverse voltage the current approaches:

Diode equation Medium
A. Zero
B.
C. Infinity
D.

26 At room temperature (300 K), the thermal voltage is approximately:

Diode equation Medium
A.
B.
C.
D.

27 The reverse saturation current of a silicon diode approximately doubles for every temperature rise of:

Effect of temperature on reverse saturation current Medium
A.
B.
C.
D.

28 If the reverse saturation current of a diode is at , its approximate value at is:

Effect of temperature on reverse saturation current Medium
A.
B.
C.
D.

29 In a PN junction diode, the barrier potential exists because of:

Construction and Working Medium
A. Applied external voltage
B. Diffusion of majority carriers across the junction
C. Recombination in the neutral regions
D. Thermal generation in the bulk

30 The cut-in (knee) voltage of a silicon diode and a germanium diode respectively are approximately:

V-I characteristics Medium
A. and
B. and
C. and
D. and

31 In the forward region of a diode's V-I characteristic, the dynamic resistance at a forward current is given by:

V-I characteristics Medium
A.
B.
C.
D.

32 The main function of a rectifier circuit is to:

Junction diode rectifiers Medium
A. Convert DC into AC
B. Convert AC into pulsating DC
C. Regulate output voltage
D. Amplify an AC signal

33 For a half-wave rectifier with peak output voltage , the DC (average) output voltage is:

Half wave rectifiers Medium
A.
B.
C.
D.

34 The ripple factor of an ideal half-wave rectifier is approximately:

Half wave rectifiers Medium
A.
B.
C.
D.

35 For a full-wave rectifier with peak voltage , the DC output voltage is:

Full wave rectifiers Medium
A.
B.
C.
D.

36 In a center-tapped full-wave rectifier, the Peak Inverse Voltage (PIV) across each diode is:

Full wave rectifiers Medium
A.
B.
C.
D.

37 The maximum theoretical rectification efficiency of a full-wave rectifier is approximately:

Efficiency Medium
A.
B.
C.
D.

38 Compared to a half-wave rectifier, a full-wave rectifier has a ripple factor that is:

Efficiency Medium
A. The same
B. Higher (about )
C. Lower (about )
D. Exactly zero

39 A Zener diode used as a voltage regulator is always operated in which region?

Zener diode Medium
A. Reverse breakdown region
B. Forward conduction region
C. Saturation region
D. Cut-off region

40 The Zener breakdown mechanism (as opposed to avalanche) dominates in diodes that are:

Zener diode Medium
A. Lightly doped with a wide depletion region
B. Heavily doped with a thin depletion region
C. Forward biased strongly
D. Undoped intrinsic semiconductors

41 A silicon diode has a reverse saturation current at . Assuming ideality factor and , what forward voltage is required to produce a forward current of ?

Diode equation Hard
A. Approximately
B. Approximately
C. Approximately
D. Approximately

42 The reverse saturation current of a diode doubles for every rise in temperature. If at , what is its approximate value at ?

Effect of temperature on reverse saturation current Hard
A.
B.
C.
D.

43 For an abrupt PN junction, the transition (depletion) capacitance varies with reverse bias voltage as:

Junction capacitance Hard
A.
B.
C.
D.

44 A full-wave bridge rectifier feeds a purely resistive load with a peak secondary voltage of . Neglecting diode drops, what is the DC (average) output voltage?

Full wave rectifiers Hard
A. Approximately
B. Approximately
C. Approximately
D. Approximately

45 A half-wave rectifier delivers an RMS load current of . What is the DC component of the load current?

Half wave rectifiers Hard
A. Approximately
B. Approximately
C. Approximately
D. Approximately

46 The maximum theoretical rectification efficiency of an ideal half-wave rectifier and a full-wave rectifier are respectively:

Efficiency Hard
A. and
B. and
C. and
D. and

47 In a PN junction, the P-side doping is 10 times greater than the N-side doping (). How does the depletion width on each side compare?

Depletion region Hard
A. P-side depletion width is times the N-side width
B. Both sides have equal depletion widths
C. P-side depletion width is 10 times the N-side width
D. N-side depletion width is 10 times the P-side width

48 A Zener regulator uses a Zener with from a supply. If the load draws , what current flows through the Zener?

Zener diode Hard
A. Approximately
B. Approximately
C. Approximately
D. Approximately

49 The dynamic (AC) resistance of a diode at a forward operating current of , assuming and , is:

V-I characteristics Hard
A.
B.
C.
D.

50 In a center-tapped full-wave rectifier with peak load voltage , the Peak Inverse Voltage (PIV) across each diode is:

Full wave rectifiers Hard
A.
B.
C.
D.

51 A full-wave rectifier output has a ripple factor of (unfiltered). If a capacitor filter reduces the ripple to , the improvement factor in ripple is approximately:

Junction diode rectifiers Hard
A.
B.
C.
D.

52 A diode carries at forward voltage and at . For and , the voltage change is approximately:

Diode equation Hard
A.
B.
C.
D.

53 For a silicon diode, the forward voltage drop at constant current changes with temperature at approximately:

Effect of temperature on reverse saturation current Hard
A.
B.
C.
D.

54 For a one-sided abrupt (p+ n) junction, the depletion width is essentially determined by:

Depletion region Hard
A. The heavily-doped P-side doping concentration
B. The geometric mean of both doping levels
C. Neither doping level, only the junction area
D. The lightly-doped N-side doping concentration

55 A Zener diode has a breakdown voltage of and a dynamic resistance of . If the Zener current changes by , the change in the regulated output voltage is:

Zener diode Hard
A.
B.
C.
D.

56 Two identical silicon diodes are connected in series and forward-biased by a source through a resistor. Compared to a single diode at the same current, the total voltage drop across the pair is:

V-I characteristics Hard
A. Twice the single-diode drop
B. Half the single-diode drop
C. times the single-diode drop
D. Equal to the single-diode drop

57 The diffusion capacitance of a forward-biased diode is primarily associated with:

Junction capacitance Hard
A. The parasitic lead inductance
B. The reverse leakage current
C. The immobile ions in the depletion layer
D. Storage of minority charge carriers in the neutral regions

58 A half-wave rectifier has a load resistance of and diode forward resistance of , with . The DC output power delivered to the load is approximately:

Half wave rectifiers Hard
A.
B.
C.
D.

59 During the manufacture of a PN junction, the built-in potential barrier increases when:

Construction and Working Hard
A. The junction cross-sectional area is increased
B. Temperature is raised significantly
C. Doping concentrations on both sides are increased
D. The reverse bias is removed

60 A full-wave rectifier and a half-wave rectifier deliver the same peak current . The ratio of the DC output current of the full-wave to that of the half-wave rectifier is:

Full wave rectifiers Hard
A.
B.
C.
D.
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Unit 2