How to get started?
Here we adopt a different approach compared to other textbooks. We will not introduce you first to the most common diode circuits, and we will not explain how they work and make all relevant calculations. The idea is that you can make this analysis yourself after going through this section. It contains a lot of assessments that build up in complexity and that should allow you to gain more understanding in diode circuits.
Diodes  Level 1
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OK, let’s start. In the first level, you have to estimate when the diode(s) will conduct in the given circuit. Use the second diode model, so a small knee voltage is needed to drive a current through the diode. Ignore the breakdown voltage, i.e. you may assume it is infinitely high.
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Question 1 of 10
1. Question
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Hint
Estimate in which direction the current will flow. Next, determine whether the diode allows a nonzero current in that direction.

Question 2 of 10
2. Question
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Hint
Ask yourself if it matters that there are two resistors here. See also the hint on the previous question.

Question 3 of 10
3. Question
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Hint
This is a tricky situation. Do you see that the two diodes are in series? Remember that components in series carry the same current

Question 4 of 10
4. Question
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Hint
The basic question is still the same: in what direction does the voltage source ‘push’ the current, and does the diode conduct current in that direction?

Question 5 of 10
5. Question
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Question 6 of 10
6. Question
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Hint
Remember that a current flows from the positive end of the power supply to the negative end. As a consequence, it is impossible that both diodes conduct.

Question 7 of 10
7. Question
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Hint
Try to find a path for the current. There is only one possibility!

Question 8 of 10
8. Question
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Question 9 of 10
9. Question
The DC source generates a voltage higher than the diode’s knee voltage. Which of the statements below are true?
Correct
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Hint
Note that voltage source can also ‘sink’ a current, meaning that they receive power.

Question 10 of 10
10. Question
The DC source generates a voltage higher than the diode’s knee voltage. Which of the statements below are true?
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Diodes  Level 2
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In the next level, you will have to predict the influence of changing parameters in the circuit, e.g. what will happen if a certain resistor value increases. Again, use the second diode model. So, if the diode conducts, the voltage across the diode equals the knee voltage. If it does not conduct, the voltage is below the knee voltage.
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Question 1 of 10
1. Question
Assume that the input voltage v_{in} is sufficiently high to turn on the diode.
What happens to the currents and the voltages if v_{in} increases?Correct
Incorrect
Hint
What do you know about the voltage across a conducting diode?
And what’s the relation between the current through the diode and the current through the resistor? 
Question 2 of 10
2. Question
The same circuit as in the previous challenge, but now v_{in} remains constant (and still sufficiently high to turn on the diode).
What happens to the currents and the voltages if the resistor value decreases?Correct
Incorrect
Hint
Apply Ohm’s law to the resistor.

Question 3 of 10
3. Question
Still the same circuit, but now v_{in} is too low to turn on the diode.
What happens to the currents and the voltages if v_{in} decreases?Correct
Incorrect
Hint
What can you tell about the current? So, what’s the resistor’s voltage?

Question 4 of 10
4. Question
Assume that the input voltage v_{in} is sufficiently high to turn on the diode.
What happens to the currents and the voltages if v_{in} increases?Correct
Incorrect
Hint
What do you know about the voltage across a conducting diode?

Question 5 of 10
5. Question
Same circuit, but with v_{in} constant and still sufficiently high to turn on the diode.
What happens to the currents if R_{1} increases?Correct
Incorrect
Hint
First think what happens to the voltages and then apply Ohm’s law.

Question 6 of 10
6. Question
Still the same circuit, but now v_{in} is too low to turn on the diode.
What happens to the currents and the voltages if v_{in} decreases?Correct
Incorrect
Hint
Since the diode does not conduct, you can omit it. What’s left is a simple voltage divider.

Question 7 of 10
7. Question
Correct
Incorrect
Hint
First answer this question: What will the diode do?

Question 8 of 10
8. Question
Assume that the input voltage v_{in} is sufficiently high to turn on the diode.
What happens to the currents and the voltages if the diode’s knee voltage decreases (same v_{in})?Correct
Incorrect
Hint
Resistor R_{1} is in parallel with the diode, so it has the same voltage.

Question 9 of 10
9. Question
Assume that the input voltage v_{in} is sufficiently low to turn on the diode.
What happens to the current if the voltage of the DC source at the right increases?Correct
Incorrect
Hint
First find out what happens to the voltage across the resistor.

Question 10 of 10
10. Question
Assume that the input voltage v_{in} is sufficiently low to turn on the diode.
What happens to the currents and the voltages if the voltage of the DC source in the middle increases?
Correct
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Hint
To find out what happens to the diode current, first find out what happens to the currents through the resistors.
Diodes  Level 3
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Now we turn to numerical examples. The circuits in this level contain components with known values. Your task is to calculate the voltages and currents for these components. Assume a knee voltage of 1V.
Note: use a decimal point (not a comma) if your result contains a fractional part, e.g. V = 7.5 V.
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Question 1 of 10
1. Question
First estimate whether or not the diode conducts and then determine the voltage across each component.
Assume a knee voltage of 1 V (in all challenges).
For the diode, a positive voltage corresponds to forward bias, a negative voltage corresponds to reverse bias.
Enter positive values for all other voltages. The voltage across the voltage source is (5) V. The voltage across the diode is (1) V. The voltage across the resistor is (4) V.
Correct
Incorrect
Hint
Assume a conducting diode.
Apply KVL to find all voltages. 
Question 2 of 10
2. Question
 TheÂ current through the resistor is (40) mA. TheÂ current through the diode is (40) mA. TheÂ current through the voltage source is (40) mA.
Correct
Incorrect
Hint
One loop. One current. Apply Ohm’s law.

Question 3 of 10
3. Question
First estimate whether or not the diode conducts and then determine the voltage across each component.
For the diode, a positive voltage corresponds to forward bias. The voltage across the resistor is (0) V. The voltage across the diode is (3) V.
Correct
Incorrect
Hint
Assume a nonconducting diode. What’s the current through the resistor then? And its voltage?

Question 4 of 10
4. Question
First estimate whether or not the diode conducts and then determine the voltage across each component.
 The voltage across the diode is (1) V. The voltage across the upper resistor is (3) V. The voltage across the lower resistor is (3) V.
Correct
Incorrect
Hint
The two resistors are equal, and have the same current, so what can you tell about the resistors’ voltages?

Question 5 of 10
5. Question
First estimate whether or not the diode conducts and then determine the voltage across each component.
 The voltage across the diode is (1) V. The voltage across the right resistor is (1) V. The voltage across the left resistor is (4) V.
Correct
Incorrect
Hint
The right resistor is in parallel with the diode, so they have the same voltage.
Apply KVL to find the other resistor’s voltage. 
Question 6 of 10
6. Question
 TheÂ current through the right resistor is (4) mA. TheÂ current through the left resistor is (16) mA. TheÂ current through the diode is (12) mA.
Correct
Incorrect
Hint
Apply Ohm’s Law to the resistors, and KCL for the diode.

Question 7 of 10
7. Question
First estimate whether or not the diode conducts and then determine the voltage across each component.
 The voltage across the upper resistor is (2) V. The voltage across the lower resistor is (8) V. The voltage across the diode is (8) V.
Correct
Incorrect
Hint
If the diode is off, what’s left is a voltage divider.

Question 8 of 10
8. Question
 TheÂ current through the upper resistor is (10) mA. TheÂ current through the lower resistor is (10) mA. TheÂ current through the diode is (0) mA.
Correct
Incorrect
Hint
This should be easy now.

Question 9 of 10
9. Question
First estimate whether or not the diode conducts and then determine the voltage across each component.
 The voltage across the diode is (1) V. The voltage across the lower resistor is (0) V. The voltage across the upper resistor is (5) V.
Correct
The voltage across the rightmost resistor is 0 V, because the diode voltage and the voltage across the rightmost voltage source cancel out. Applying KVL in the right loop (counterclockwise) yields: 1 V (source) + 1 V (diode) = 0 V (resistor).
Incorrect
The voltage across the rightmost resistor is 0 V, because the diode voltage and the voltage across the rightmost voltage source cancel out. Applying KVL in the right loop (counterclockwise) yields: 1 V (source) + 1 V (diode) = 0 V (resistor).

Question 10 of 10
10. Question
 TheÂ current through the upper resistor is (100) mA. TheÂ current through the lower resistor is (0) mA. TheÂ current through the diode is (100) mA.
Correct
Incorrect
Hint
Same as before: Ohm’s Law for the resistors and KCL for the diode.
Diodes  Level 4
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Still some numerical challenges in this level, now with increased complexity. Only voltages are asked for now. Currents can be found by applying Ohm’s Law and KCL.
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Question 1 of 6
1. Question
First find out which diodes conduct then determine the voltage across each component.
Assume a knee voltage of 1 V (in all challenges).
For the diode, a positive voltage corresponds to forward bias. The voltage across the upper diode is (1) V. The voltage across the lower diode is (1) V. The voltage across the resistor is (4) V.
Correct
Incorrect
Hint
Assume conducting diodes.
Apply KVL to find the resistor voltage. 
Question 2 of 6
2. Question
 The voltage across each diode is (1) V. The voltage across the upper resistor is (1.5) V. The voltage across the lower resistor is (7.5) V.
Correct
Incorrect
Hint
Diodes in series are all off, or all on.
One way to find the resistor voltages is to first calculate the current by applying KVL to the loop. 
Question 3 of 6
3. Question
First find out which diodes conduct then determine the voltage across each component.
For the diode, a positive voltage corresponds to forward bias. The voltage across the right diode (D2) is (1) V. The voltage across the left diode (D1) is (1) V. The voltage across the resistor is (4) V.
Correct
Incorrect
Hint
The two diodes are in parallel, so the absolute values of their voltages are equal.
Take care of the polarity. 
Question 4 of 6
4. Question
First find out which diodes conduct then determine the voltage across each component.
For the diode, a positive voltage corresponds to forward bias.
Enter positive values for all other voltages.
Watch out! The questions are not in a logical order. The voltage across the resistor is (2) V. The voltage across the left diode (D1) is (1) V. The voltage across the right diode (D2) is (5) V.
Correct
Incorrect
Hint
Start solving the loop with the conducting diode.
Then apply KVL to the other loop. 
Question 5 of 6
5. Question
First find out which diodes conduct then determine the voltage across each component.
For the diode, a positive voltage corresponds to forward bias.
Watch out! The questions are not in a logical order. The voltage across the upper left diode (D1) is (1) V. The voltage across the upper right diode (D2) is (14) V. The voltage across the lower left diode (D3) is (14) V. The voltage across the lower right diode (D4) is (1) V. The voltage across the resistor is (13) V.
Correct
Incorrect
Hint
Sorry. You’re on your own now.

Question 6 of 6
6. Question
 If the switch is open, the current through the resistor is (20) mA. If the switch is closed, the current through the resistor is (30) mA.
Correct
If the switch is closed, the rightmost diode will conduct. As a result, there is only 1 V across the two other diodes. This is not sufficient to make them conduct (they need 2 V in total).
Incorrect
If the switch is closed, the rightmost diode will conduct. As a result, there is only 1 V across the two other diodes. This is not sufficient to make them conduct (they need 2 V in total).
About mistakes
A little note on mistakes. Yes, mistakes are important. If you know that you made a mistake, you have learned something, and that’s what this course wants to help you with. In the following example, a mistake is made. Sometimes it is indeed not so obvious to predict whether or not a diode will conduct. You could start with an assumption, and then check whether the result makes sense.
What makes no sense?
 A negative current through the diode. A diode voltage below the knee voltage goes together with zero current.
 A diode voltage higher than the knee voltage. If there is a current, then the diode voltage equals the knee voltage.
Diodes  Level 5
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Solve the next challenges. In some cases, you will have to make a mistake.
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Question 1 of 5
1. Question
 The voltage across the 100 ohm resistor is (1) V. The voltage across the 50 ohm resistor is (0.5) V. The voltage across the diode is (0.5) V. The current through the 100 ohm resistor is (10) mA. The current through the 50 ohm resistor is (10) mA. The current through the diode is (0) mA.
Correct
Incorrect
Hint
We know that the diode does not conduct.

Question 2 of 5
2. Question
Now, make a mistake on purpose, and assume a conducting diode.
Calculate the current through the diode. Take care of the sign. The current through the diode is (1.33) mA. (Enter a number with 3 digits.)
Correct
Incorrect
Hint
First find the voltages across the resistors. Then apply Ohm’s Law to them. Finally apply KCL to find the diode’s current.

Question 3 of 5
3. Question
So, the previous result was not possible: Diodes have no negative currents.
The assumption of a conducting diode was wrong.
Assume a nonconducting diode and determine all currents. The current through the 1 kohm resistor is (1) mA. The current through the 3 kohm resistor is (1) mA. The current through the diode is (0) mA.
Correct
Incorrect
Hint
If the diode does not conduct, you can think away the middle branch. What’s left is a simple voltage divider.

Question 4 of 5
4. Question
 The voltage across the 100 ohm resistor is (1) V. The voltage across the 400 ohm resistor is (4) V. The voltage across the 500 ohm resistor is (0) V. The voltage across the left diode (D1) is (1) V. The voltage across the right diode (D2) is (5) V.
Correct
Incorrect
Hint
First solve the loop with the conducting diode. Then do the other loop.

Question 5 of 5
5. Question
 The voltage across the 100 ohm resistor is (8) V. The voltage across the left diode (D1) is (1) V. The voltage across the right diode (D2) is (2) V.
Correct
Incorrect
Hint
Take care of the polarities here. A negative voltage for a diode means reverse bias.
For resistors, fill in a positive voltage, but make sure you know in which direction the current flows.
Node analysis
In some cases it might be needed to derive and solve an equation in order to find all voltages and currents. In this book, node analysis will be used mostly, as in the example below.
Here are the steps:
 Label the voltage at the upper node v_{o}. Remember that this refers to the voltage at this node relative to ground.
 The voltage at the node to which the diode’s cathode is attached is then v_{o}1V, due to the 1V voltage drop across the diode.
 Estimate the direction of all currents entering and leaving the upper node. Note that it is not crucial to make correct estimates, since another direction will be reflected in your equation.
 Set up the equation by applying KCL in the upper node. In essence you apply Ohm’s Law to each resistor. Make sure you fill in the correct voltages.
 Now solve the equation for v_{o}. (Up to you.)
Diodes  Level 6
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You might need pen and paper now, to write down the equations…
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Question 1 of 2
1. Question
 The voltage across the right resistor (750 ohm) is (3) V. The voltage across the upper resistor (250 ohm) is (3) V. The voltage across the middle resistor (250 ohm) is (2) V. The voltage across the diode is (1) V. The current through the right resistor (750 ohm) is (4) mA. The current through the upper resistor (250 ohm) is (12) mA. The current through the middle resistor (250 ohm) is (8) mA. The current through the diode is (8) mA.
Correct
Incorrect
Hint
Solve the equation in the previous example first.

Question 2 of 2
2. Question
 The voltage across the lower resistor (300 ohm) is (2) V. The voltage across the upper left resistor (900 ohm) is (7) V. The voltage across the upper right resistor (900 ohm) is (1) V. The voltage across the diodeÂ is (1)V.
Correct
Incorrect
Hint
Look again at the example in Figure 2.17.
The voltage at the upper right node is a numerical value, if you assume that the diode is on.
Diodes  Level 7a
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The goal of the next level is to find the relation between some input voltage and some output voltage. We will adopt a threestep approach. First, assume that the diode is on, and find a formula that expresses the output voltage as a function of the input voltage. Second, do the same thing, but now you assume that the diode is off. Third, combine both results. The input voltage at which both formula’s yield the same result is called the threshold voltage, and it is the voltage at which the diode starts or stops conducting.
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Question 1 of 9
1. Question
Suppose the diode conducts (knee voltage = 1V).
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (1). The value of B is (1) V. The value of C is (1).
Correct
Incorrect
Hint
Apply KVL in the loop.

Question 2 of 9
2. Question
Now suppose the diode does not conduct.
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive. The value of A is (0). The value of B is (0) V. The value of C is (1).
Correct
Incorrect
Hint
What is the current through the resistor if the diode is off? And its voltage?

Question 3 of 9
3. Question
Which graph reflects the relation between the input voltage v_{in} and the output voltage v_{out}?
And what is the value of the threshold voltage V_{T}?Correct
Incorrect
Hint
The dashed lines represent the solutions of the two previous steps. Find out first when the diode conducts (for large negative or for large positive input voltages?).
In order to find the threshold voltage V_{T}, find the intersection between the two lines. Their equations are already found in the previous two questions. 
Question 4 of 9
4. Question
Suppose the diodes conduct (knee voltage = 1V).
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (0). The value of B is (2) V. The value of C is (1).
Correct
Incorrect
Hint
This should be easy.

Question 5 of 9
5. Question
Now suppose the diodes do not conduct.
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (1). The value of B is (0) V. The value of C is (1).
Correct
Incorrect
Hint
What is the current through the resistor if the diode is off? And its voltage? Now apply KVL.

Question 6 of 9
6. Question
Which graph reflects the relation between the input voltage v_{in} and the output voltage v_{out}?
And what is the value of the threshold voltage V_{T}?Correct
Incorrect
Hint
The dashed lines represent the solutions of the two previous steps. Find out first when the diode conducts (for large negative or for large positive input voltages?).
In order to find the threshold voltage V_{T}, find the intersection between the two lines. Their equations are already found in the previous two questions. 
Question 7 of 9
7. Question
Suppose the diode conducts (knee voltage = 1V).
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (1). The value of B is (1) V. The value of C is (2).
Correct
Incorrect
Hint
You can do this in one step if you combine KVL with the voltage division formula.

Question 8 of 9
8. Question
Now suppose the diode does not conduct.
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (0). The value of B is (0) V. The value of C is (1).
Correct
Incorrect
Hint
What is the current through the resistor if the diode is off? And its voltage?

Question 9 of 9
9. Question
Which graph reflects the relation between the input voltage v_{in} and the output voltage v_{out}?
And what is the value of the threshold voltage V_{T}?Correct
Incorrect
Hint
The dashed lines represent the solutions of the two previous steps. Find out first when the diode conducts (for large negative or for large positive input voltages?).
In order to find the threshold voltage V_{T}, find the intersection between the two lines. Their equations are already found in the previous two questions.
Diodes  Level 7b
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A bit harder…
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Question 1 of 9
1. Question
Suppose the diode conducts (knee voltage = 1V).
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (0). The value of B is (1) V. The value of C is (1).
Correct
Incorrect
Hint
The 200 ohm resistor is in parallel with the diode, so they have the same voltage.

Question 2 of 9
2. Question
Now suppose the diode does not conduct.
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive. The value of A is (2). The value of B is (0) V. The value of C is (3).
Correct
Incorrect
Hint
If the diode is off, what’s left is a voltage divider.

Question 3 of 9
3. Question
Which graph reflects the relation between the input voltage v_{in} and the output voltage v_{out}?
And what is the value of the threshold voltage V_{T}?Correct
Incorrect
Hint
The dashed lines represent the solutions of the two previous steps. Find out first when the diode conducts (for large negative or for large positive input voltages?).
In order to find the threshold voltage V_{T}, find the intersection between the two lines. Their equations are already found in the previous two questions. 
Question 4 of 9
4. Question
Suppose the diodes conduct (knee voltage = 1V).
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (0). The value of B is (1) V. The value of C is (1).
Correct
Incorrect
Hint
Take care of the sign (and the diode’s polarity).

Question 5 of 9
5. Question
Now suppose the diodes do not conduct.
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (4). The value of B is (0) V. The value of C is (5).
Correct
Incorrect
Hint
If the diode is off, what’s left is a voltage divider, and the diode is parallel with one of the resistors.

Question 6 of 9
6. Question
Which graph reflects the relation between the input voltage v_{in} and the output voltage v_{out}?
And what is the value of the threshold voltage V_{T}?Correct
Incorrect
Hint
The dashed lines represent the solutions of the two previous steps. Find out first when the diode conducts (for large negative or for large positive input voltages?).
In order to find the threshold voltage V_{T}, find the intersection between the two lines. Their equations are already found in the previous two questions. 
Question 7 of 9
7. Question
Suppose the diode conducts (knee voltage = 1V).
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (1). The value of B is (1) V. The value of C is (1).
Correct
Incorrect
Hint
Apply KVL in the outer loop.

Question 8 of 9
8. Question
Now suppose the diode does not conduct.
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (4). The value of B is (0) V. The value of C is (7).
Correct
Incorrect
Hint
If the diode is off, what’s left is a voltage divider.

Question 9 of 9
9. Question
Which graph reflects the relation between the input voltage v_{in} and the output voltage v_{out}?
And what is the value of the threshold voltage V_{T}?Correct
Incorrect
Hint
The dashed lines represent the solutions of the two previous steps. Find out first when the diode conducts (for large negative or for large positive input voltages?).
In order to find the threshold voltage V_{T}, find the intersection between the two lines. Their equations are already found in the previous two questions.
Diodes  Level 7c
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Question 1 of 9
1. Question
Suppose the diode conducts (knee voltage = 1V).
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (0). The value of B is (2) V. The value of C is (1).
Correct
Incorrect
Hint
Apply KVL in the right loop.

Question 2 of 9
2. Question
Now suppose the diode does not conduct.
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive. The value of A is (3). The value of B is (0) V. The value of C is (4).
Correct
Incorrect
Hint
If the diode is off, what’s left is a voltage divider.

Question 3 of 9
3. Question
Which graph reflects the relation between the input voltage v_{in} and the output voltage v_{out}?
And what is the value of the threshold voltage V_{T}?Correct
Incorrect
Hint
The dashed lines represent the solutions of the two previous steps. Find out first when the diode conducts (for large negative or for large positive input voltages?).
In order to find the threshold voltage V_{T}, find the intersection between the two lines. Their equations are already found in the previous two questions. 
Question 4 of 9
4. Question
Suppose the diodes conduct (knee voltage = 1V).
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (3). The value of B is (3) V. The value of C is (7).
Correct
Incorrect
Hint
Node analysis is needed now. See Level 6 for equivalent challenges.

Question 5 of 9
5. Question
Now suppose the diodes do not conduct.
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (3). The value of B is (0) V. The value of C is (4).
Correct
Incorrect
Hint
If the diode is off, what’s left is a voltage divider.

Question 6 of 9
6. Question
Which graph reflects the relation between the input voltage v_{in} and the output voltage v_{out}?
And what is the value of the threshold voltage V_{T}?Correct
Incorrect
Hint
The dashed lines represent the solutions of the two previous steps. Find out first when the diode conducts (for large negative or for large positive input voltages?).
In order to find the threshold voltage V_{T}, find the intersection between the two lines. Their equations are already found in the previous two questions. 
Question 7 of 9
7. Question
Suppose the diode conducts (knee voltage = 1V).
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (1). The value of B is (5) V. The value of C is (6).
Correct
Incorrect
Hint
Again node analysis is needed, as in Level 6.

Question 8 of 9
8. Question
Now suppose the diode does not conduct.
What is then the relation between the input voltage v_{in} and the output voltage v_{out}?
The formula takes the form v_{out}=(A.v_{in}+B)/C.
Find the values for A, B and C.
Some guidelines:
– Find the smallest values for A, B and C.
– C is always positive.
– Take care of the sign. The value of A is (0). The value of B is (0) V. The value of C is (1).
Correct
Incorrect
Hint
This should be easy.

Question 9 of 9
9. Question
Which graph reflects the relation between the input voltage v_{in} and the output voltage v_{out}?
And what is the value of the threshold voltage V_{T}?Correct
Incorrect
Hint
The dashed lines represent the solutions of the two previous steps. Find out first when the diode conducts (for large negative or for large positive input voltages?).
In order to find the threshold voltage V_{T}, find the intersection between the two lines. Their equations are already found in the previous two questions.
Why is there only quiz about diodes. What about transistors and other stuffs.
Because this site is workinprogress.
Transistors and other stuff is not ready yet.
Great online course!
Small remark, nothing major.. At diodes, level 3, question 2, the answer counts 7,5 as incorrect while the correct answer is 7.5 (notice the comma).
And actually, you ask the voltage across the upper resistor twice in the same question.
Oops.
Now it should be OK.
Indeed, you have to use the decimal point notation.
I added a note in the instructions.
Thanks.
Very good online course and exercises. Help me a lot with the diode!
Perfect exercises. Hope we see these EXACT questions on the exam! Thanks prof.
Hmm, I NEVER ask EXACTLY the same questions, but I often ask ALMOST the same question.
You’re welcome.
It’s easier and more efficient to learn in this systematic and progressive way. Excellent tool! Can’t wait to see more chapters in this form! I think it will help us review past knowledge and prepare well for the exam, haha~
Diodes level 2: question 10. I can’t see why the current throug the diode will increase, I thought it wouldn’t change at all…
If the DC source voltage increases, the voltage at the diode’s cathode will also increase.
As a result, the current through both resistors will increase, so also the current through the diode (obeying KCL).
I thought the current trough both resistors would increase with the same amount, leaving the current throug the diode unchanged.
But even in that case the current through the diode would increase, since the diode current is the sum of the two resistor currents.
Ok, I think I get it. Is it true that current through the diode is sum of resistors current only when voltagesource in the middle is 7V or higher?
Thank you for your help!
Not necessarily. It depends on the value of both v_{in} and the DC source, and these are not known.
I think what you mean is that the current through the diode is the sum of resistors current only when the diode is on.
For level 7a ,question number 4, after applying kvl i get Vo= Vin – 2 which is wrong. could you please give me correct equation?
is it simply the total voltage across two diodes?
Indeed.
What you’ve calculated is the voltage across the resistor.
Correct equations will always be given after you have answered the question.
Thank you
Diodes lvl 3: question 9
I can’t see why the voltage across the lower resistor is 0…
The voltage across the rightmost resistor is 0 V, because the diode voltage and the voltage across the rightmost voltage source cancel out. Applying KVL in the right loop (counterclockwise) yields: 1 V (source) + 1 V (diode) = 0 V (resistor).
Wouldnt it be handy to show up the diodic model sometimes? With hints and faults?
Dear Joren.
This might indeed be handy, but please help me on this. Can you suggest for which question(s) this might be useful?
Hints are already included in most questions. If more or other hints are needed, tell me again for which questions.
What do you mean with faults?
Level 7a: question 7: I think B has to be 1. If not, can you explain me why it is +1?
B is +1. Probably the polarity of your voltage across the diode is wrong.
Note that the current goes counterclockwise if the diode conducts.
Level 7c: Are you sure the answers to the last two questions are correct?
Well, I checked it again, and find the same results.
What did you find (and why)?
In 7c question 7, why is it a=1, b=5, c=6; I tought it would be 1, 5, 5?
Well, the answer is correct though (c=6).
I can’t tell where you made a mistake.
Apply node analysis in the upper node, and label it (Vout + 1V).
Can you maybe consider, when we click on an image to open it in a new tab.
Because now when you click an image and you’re in the middle of a quiz, you have to do the quiz all over again, because you need to go back to the page. (reload it)
That would be quite difficult to achieve.
I am using a plugin for the quiz, and I can’t change the code.
Perhaps you could click with the mouse’s right button and indicate to open in a new tab?
At question 7 of diodes: I think it would be a little easier to have a drawing of the circuit at the question of the graphic, cause I forget every time how my diode is situated
Good suggestion. I’ve made the changes.
Level 7c , question 7. Why is is the value of B equal 5 in place of 1?? I really don’t understand. Can you please explain, or see if I made a mistake? Thanks
See level 6. You can solve this by setting up an equation using node analysis.
Perhaps you could show me your first equation.
in section 7.a there is the equation vout=(A.vin+B)/C. what values do A, B and C stand for?
These are the values you have to calculate!
yes but what do they represent? for example A= current through the diode
Ah ok, well they do not represent some physical quantity. You could say that A/C is an amplification factor (that often is smaller than 1 though) and that B/C is a voltage.
then i do not understand how it works, is there a simple explanation somewhere for the calculation?
There’s no strict methodology to find A, B and C.
The goal is to find the relation between v_{in} and v_{out}, and to put that relation in a specific format.
E.g. if you find that v_{out} = v_{in}/2, than A would be 1, B = 0 and C = 2.
oke thank you
Diodes – Level 5
Question (2)
Hello,
I am having a difficult time to identify in which direction the current flows! and also what is the purpose of the 3v in the middle?
Thank you!! ðŸ˜€
If there is a current through the diode, it should be a forward current, so in the direction of the arrow in the symbol.
There is not a specific purpose for the 3V source.
Level 5 Question 5, I don’t know why the voltage across 100ohm resistor is 8v because I found 6v from my calculation.
Take care of the polarities. When applying KVL, the voltages of the 8V source and the 1V source ADD UP!