Discrete Semiconductor Devices and Circuits

Rectifying Diodes

19 questions By Tony R. Kuphaldt

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Question 7 of 19

Complete the following table of values for this diode circuit, assuming a typical forward voltage drop of 0.72 volts for the diode:

Reveal answer

Notes:
Have your students explain all their steps and calculations for solving this problem, so that you and their classmates can examine their problem-solving processes in an open and constructive forum.
Question 8 of 19

Predict how all component voltages and currents in this circuit will be affected as a result of the following faults. Consider each fault independently (i.e. one at a time, no multiple faults):

Diode D₁ fails open:

Diode D₁ fails shorted:

Resistor R₁ fails open:

Solder bridge (short) past resistor R₁:

For each of these conditions, explain why the resulting effects will occur.

Reveal answer

Diode D₁ fails open: No current in circuit, no voltage across R₁, full source voltage across D₁.

Diode D₁ fails shorted: Increased current in circuit, full source voltage across R₁, little voltage across D₁.

Resistor R₁ fails open: No current in circuit, no voltage across D₁, full source voltage across R₁.

Solder bridge (short) past resistor R₁: Large current in circuit, no voltage across R₁, full source voltage across D₁, D₁ will most likely overheat and fail.

Notes:
The purpose of this question is to approach the domain of circuit troubleshooting from a perspective of knowing what the fault is, rather than only knowing what the symptoms are. Although this is not necessarily a realistic perspective, it helps students build the foundational knowledge necessary to diagnose a faulted circuit from empirical data. Questions such as this should be followed (eventually) by other questions asking students to identify likely faults based on measurements.
Question 9 of 19

Predict how all component voltages and currents in this circuit will be affected as a result of the following faults. Consider each fault independently (i.e. one at a time, no multiple faults):

Diode D₁ fails open:

Diode D₁ fails shorted:

Resistor R₁ fails open:

Resistor R₂ fails open:

For each of these conditions, explain why the resulting effects will occur.

Reveal answer

Diode D₁ fails open: No current in circuit, no voltage across R₁, no voltage across R₂, full source voltage across D₁.

Diode D₁ fails shorted: Increased current in circuit, increased voltage across R₁, increased voltage across R₂, little voltage across D₁.

Resistor R₁ fails open: No current in circuit, no voltage across D₁, full source voltage across R₁, no voltage across R₂.

Resistor R₂ fails open: No current in circuit, no voltage across D₁, no voltage across R₁, full source voltage across R₂.

Notes:
The purpose of this question is to approach the domain of circuit troubleshooting from a perspective of knowing what the fault is, rather than only knowing what the symptoms are. Although this is not necessarily a realistic perspective, it helps students build the foundational knowledge necessary to diagnose a faulted circuit from empirical data. Questions such as this should be followed (eventually) by other questions asking students to identify likely faults based on measurements.