Unit 2 - Practice Quiz

1 What happens when a p-type semiconductor is suitably joined to an n-type semiconductor?

2 In an open-circuited p-n junction at thermal equilibrium, the Fermi level is:

3 Which of the following are the majority charge carriers in the n-region of a p-n diode?

4 The movement of charge carriers in a semiconductor under the influence of an applied electric field is called:

5 What is the typical knee voltage (cut-in voltage) for a standard Silicon p-n junction diode?

6 How does the reverse saturation current of a p-n junction diode behave with an increase in temperature?

7 The resistance offered by a diode to a steady direct current (DC) is called:

8 Which capacitance is predominantly significant when a p-n junction diode is reverse-biased?

9 The time required for a diode to switch from a forward-biased state to a reverse-biased state is known as:

10 A Zener diode is primarily used in electronic circuits as a:

11 Under which operating condition does a Light Emitting Diode (LED) emit light?

12 Which unique characteristic is exhibited by a Tunnel diode?

13 In a p-I-n diode, what does the 'I' stand for?

14 What is the primary function of a rectifier circuit?

15 How many diodes are required to construct a standard bridge full-wave rectifier?

16 What is the theoretical ripple factor of a basic half-wave rectifier?

17 A circuit that removes a specific portion of a signal waveform without distorting the remaining part is called a:

18 Which circuit is primarily used to shift the DC level of an AC output signal to a different voltage level?

19 The 1N4001 to 1N4007 series of diodes are most commonly classified as:

20 What is the primary difference among the various diodes in the 1N4001 to 1N4007 series?

21 In the energy band diagram of an open-circuited p-n junction, how does the Fermi level behave across the junction at thermal equilibrium?

22 The built-in potential of a p-n junction depends on the doping concentrations and . If the doping concentration on the p-side () is increased by a factor of 10, how does the built-in potential change at room temperature (assuming )?

23 In a forward-biased p-n junction diode, the total current across the junction is primarily governed by which of the following mechanisms?

24 A silicon diode operates at a forward voltage of . If the ideality factor , how does the forward current change if the forward voltage is increased by at room temperature ()?

25 For a silicon p-n junction diode operating at a constant forward current, what is the approximate rate of change of the forward voltage drop with respect to temperature?

26 If the reverse saturation current of a diode is at , what will be its approximate value at ?

27 A silicon diode is operating at room temperature with an ideality factor . If the DC bias current is , what is the approximate dynamic resistance of the diode?

28 Which of the following statements correctly compares the transition capacitance () and diffusion capacitance () in a p-n junction diode?

29 For an abrupt (step-graded) p-n junction, how does the transition capacitance vary with the applied reverse bias voltage (assuming is the built-in potential)?

30 When a forward-biased diode is suddenly switched to a reverse bias, a large reverse current flows for a short duration. This specific time interval, during which the stored minority charge is removed from the neutral regions, is called:

31 In a simple Zener voltage regulator circuit, what condition must be satisfied to ensure the Zener diode maintains regulation when the load current varies?

32 A Light Emitting Diode (LED) emits light due to the recombination of electrons and holes. If an LED is required to emit red light (wavelength ), what should be the approximate bandgap energy of the semiconductor material?

33 Which of the following statements best describes the utility of the heavily doped regions in a Tunnel Diode?

34 A p-I-n diode is frequently used as a radio frequency (RF) switch. What characteristic of the intrinsic layer allows it to perform this function effectively?

35 A center-tapped full-wave rectifier is supplied by a transformer with a secondary peak voltage of across each half. What is the Peak Inverse Voltage (PIV) rating required for the diodes?

36 An AC signal with a peak-to-peak voltage of (ranging from to ) is passed through a positive clamper circuit with an ideal diode. Assuming no load, what will be the approximate output voltage range?

37 In a practical clamper circuit utilizing a capacitor and a load resistor , for the clamping action to work properly without significant discharge of the capacitor, how should the time constant relate to the input signal's time period ?

38 A series positive clipper circuit is constructed using a silicon diode in series with the load. An alternating sinusoidal voltage of peak value is applied to the input. Assuming a diode forward drop of , what is the peak voltage of the resulting output waveform across the load?

39 The 1N400x series of diodes (1N4001 through 1N4007) are general-purpose rectifiers. Which of the following electrical specifications distinctly varies across the different part numbers in this family?

40 According to typical datasheets for the 1N4007 diode, the maximum average forward rectified current is . If used in a half-wave rectifier circuit delivering an average load current of , what is the most likely consequence?

41 In an open-circuited silicon p-n junction at thermal equilibrium, if the p-side is degenerately doped such that the Fermi level lies exactly at the valence band edge , and the n-side is doped at , what is the theoretical built-in potential at ? (Assume , , and )

42 A silicon diode is operated at a constant forward current. Its forward voltage is at . If the reverse saturation current doubles for every rise in temperature, what is the approximate forward voltage at ?

43 In a forward-biased step junction, the ratio of hole diffusion current to electron diffusion current crossing the depletion region is predominantly determined by which of the following?

44 At very high forward bias currents (high-level injection condition), the ideality factor of a silicon p-n junction diode approaches a specific value. What is this value and what is the underlying physical cause?

45 A silicon diode operates at () with an ideality factor . It is biased such that its forward voltage is . Assuming negligible bulk resistance, what is the exact ratio of its DC static resistance to its AC dynamic resistance ?

46 In a linearly graded p-n junction, the transition capacitance under reverse bias is proportional to . Simultaneously, the diffusion capacitance varies with forward current . Which of the following describes the value of and the dependency of on ?

47 During the reverse recovery of a p-n junction diode, the storage time is given approximately by . If a circuit is designed such that the initial reverse current is strictly limited to of the forward current , what is the relationship of to the minority carrier lifetime ?

48 A temperature-compensated voltage reference of is formed by placing a Zener diode in series with a forward-biased silicon p-n diode (which has a temperature coefficient of ). To achieve zero temperature drift for the combined unit, what must be the breakdown voltage and temperature coefficient of the Zener diode alone?

49 In the Negative Differential Resistance (NDR) region of a Tunnel diode, the current decreases as the forward bias voltage increases. Which quantum mechanical condition primarily causes this reduction in tunneling current?

50 When designing a microwave RF switch using a p-I-n diode, increasing the thickness of the intrinsic (I) region presents a specific set of trade-offs. Which of the following correctly describes the effect of a thicker I-region on switch performance?

51 In a full-wave bridge rectifier equipped with a smoothing capacitor operating at mains frequency , the load draws a steady current . If the filter capacitance is doubled, how does this affect the peak-to-peak ripple voltage and the repetitive peak surge current through the diodes?

52 An input signal is applied to a clipping circuit via a series resistor . A Zener diode (with breakdown voltage , forward voltage , and dynamic zener resistance ) is connected in parallel with the output, cathode facing the positive terminal. What is the approximate maximum positive output voltage ?

53 According to the standard 1N400X series datasheet, both the 1N4001 and 1N4007 support an average forward current of . However, the 1N4007 has a Peak Repetitive Reverse Voltage () of compared to for the 1N4001. Which specific structural modification primarily provides this higher in the 1N4007?

54 An LED is fabricated from a direct bandgap semiconductor with . The non-radiative recombination lifetime is and the radiative recombination lifetime is . What is the approximate emission wavelength and the internal quantum efficiency ? (Assume )

55 For a one-sided abrupt junction, the maximum electric field occurs at the metallurgical junction. If the donor concentration in the n-region is increased by a factor of 4, how does the magnitude of change? (Assume the built-in potential remains roughly constant for this approximation)

56 A transformer utilized in a full-wave center-tapped rectifier has a Transformer Utilization Factor (TUF) of $0.693$, whereas a bridge rectifier has a TUF of $0.812$. What is the primary analytical reason for the center-tapped configuration having a lower TUF?

57 A practical negative clamper circuit (comprising a capacitor , a diode pointing downwards to ground, and a load ) is fed with an AC input . Assuming to maintain less than tilt, what is the absolute minimum Peak Inverse Voltage (PIV) rating required for the diode, and when does it experience this voltage?

58 A silicon p-n junction diode is rapidly switched from forward bias to reverse bias. Although the diffusion capacitance is mathematically much larger than the transition capacitance during forward bias, why does NOT dictate the entire reverse recovery transient time ?

59 If the temperature of an open-circuited silicon p-n junction uniformly increases from to , how does the built-in potential barrier change analytically, assuming doping concentrations remain constant?

60 During the transition from forward to reverse bias in a p-n diode, a "snap-off" or Step Recovery Diode (SRD) exhibits an unusually short transition time compared to its storage time . What specific doping profile is engineered in an SRD to force the stored charge to concentrate tightly near the junction, enabling this behavior?