Unit 3: Diode Voltage Quest - Practice Quiz

1 What does forward biasing a PN junction diode mean?

2 What happens to the depletion-region width when a PN junction diode is forward biased?

3 What happens to the barrier potential of a PN junction under forward bias?

4 Which charge carriers mainly contribute to current in a forward-biased PN junction diode?

5 What is the typical cut-in voltage of a silicon diode?

6 What is the typical cut-in voltage of a germanium diode?

7 What is another common name for the cut-in voltage of a diode?

8 How does forward current change after the diode voltage exceeds the knee voltage?

9 Which axis normally represents diode current on a voltage-current characteristic graph?

10 Which axis normally represents diode voltage on a voltage-current characteristic graph?

11 In which quadrant is the forward-bias characteristic of a diode usually plotted?

12 How does an ideal diode behave when it is forward biased?

13 What is the forward-voltage drop across an ideal conducting diode?

14 Before the forward voltage reaches the knee voltage, the diode current is generally:

15 Which instrument is connected in series to measure the forward current of a diode?

16 Which instrument is connected across a diode to measure its forward voltage?

17 Why is a resistor commonly connected in series with a forward-biased diode?

18 The static forward resistance of a diode at an operating point is calculated using which expression?

19 A diode has a forward voltage of and a forward current of . What is its static forward resistance?

20 What does the nonlinear shape of a diode's forward characteristic indicate?

21 A silicon PN junction diode is forward biased. At which voltage does its current typically begin to increase significantly?

22 For a silicon diode operating near its knee voltage, what is the most likely effect of increasing the forward voltage from to ?

23 The forward current of a diode changes from to when its forward voltage changes from to . What is its approximate dc or small-signal resistance over this interval?

24 A diode has a forward voltage of and carries a current of . What power is dissipated in the diode?

25 When the temperature of a silicon diode increases, how does its forward characteristic generally change at a fixed forward current?

26 A source is connected in series with a resistor and a silicon diode modeled with a constant forward drop of . What is the approximate diode current?

27 On a forward-bias characteristic curve, the current changes from to while the voltage changes from to . What is the approximate slope ?

28 Which feature best identifies the knee region of a PN junction diode's forward characteristic?

29 Compared with a silicon diode, a germanium diode generally shows which forward-bias characteristic?

30 Using the diode equation with the same saturation current and ideality factor, the forward voltage increases from to at room temperature. Approximately how does the current change for ?

31 For a forward-biased diode, which region of the characteristic is most accurately modeled by an approximately constant voltage drop?

32 If the forward voltage of a diode is plotted on the horizontal axis and forward current on the vertical axis, what does a steep curve indicate?

33 For a diode with ideality factor at room temperature, approximately what forward-voltage increase is required to increase the current by a factor of ten?

34 A measured diode characteristic shows a nearly straight line with a nonzero slope after the knee region. What does the slope mainly represent?

35 At room temperature, a diode carries and has ideality factor . Using , what is its approximate dynamic resistance?

36 A forward-biased diode has a current of at and at . Which conclusion is most reasonable at room temperature?

37 A diode and a resistor are connected to a dc source. If the source voltage increases while the diode remains in forward conduction, what primarily limits the increase in diode current?

38 For a forward-biased silicon diode, the current is at . If the temperature rises while the current is held constant, what happens to the forward voltage?

39 A diode's forward characteristic is initially almost horizontal and then becomes steep. What physical interpretation best matches the steep portion?

40 A load line intersects a diode's forward - characteristic at and . What does this intersection represent?

41 At , a diode carries at and at . Assuming the Shockley model and negligible series resistance, what is the ideality factor ? Use .

42 A diode at carries at . If and the term is negligible, what is its reverse saturation current?

43 A forward-biased diode operates at with at . Neglecting series resistance and assuming , what is its small-signal resistance?

44 A diode with and is biased at . Its voltage is changed by and then by relative to the bias point. What is the ratio of the upward current change to the magnitude of the downward current change?

45 A diode with and is connected in series with across a supply. At , which operating point most closely satisfies both the diode equation and the load line?

46 At , a diode with has measured terminal voltages of at and at . Assuming a constant series resistance, estimate that resistance.

47 A diode carries a fixed current at with a forward voltage of . Its saturation current doubles for every rise, while remains constant. According to the Shockley model, what is the forward voltage at ? Use at .

48 The straight-line region of a diode's forward characteristic plotted as versus has a slope of per decade at . What ideality factor does this imply?

49 A practical diode has , series resistance , and a bias current of at . What is its terminal small-signal conductance?

50 A diode with is biased at through a resistor. At , what is the small-signal change in diode current per volt of supply variation, assuming no diode series resistance?

51 For a diode with , , and , what current flows at a small forward voltage of when the full Shockley equation is used?

52 A diode operates at and with at . Neglecting series resistance, which pair gives its DC resistance and small-signal resistance, respectively?

53 At , the forward current of a PN diode doubles whenever its voltage increases by approximately over a certain low-current range. Which interpretation is most consistent with this observation?

54 For a diode described by , the measured values of are at and at . At , determine and .

55 Two parallel diodes have equal ideality factors and temperatures but saturation currents satisfying . If their total forward current is and series resistances are negligible, how is the current shared?

56 Two parallel diodes each initially carry at the same voltage. Their ideality factors are and . At , the common voltage is increased by . Neglecting series resistance, what is the new total current?

57 A diode's terminal voltage rises by as its current increases from to . If its series resistance is , what ideality factor is implied at ?

58 A diode has and an uncertain saturation current as high as . At , what is the maximum applied forward voltage that guarantees the Shockley current does not exceed ? Neglect series resistance.

59 An ideal diode with and is biased at . A zero-average sinusoidal voltage is superimposed. Neglecting relative to forward current, what is the resulting average current?

60 A diode carries at both and . Its ideality factor is , while changes from at to at . Using and , respectively, what is the forward-voltage change?