Finding Output Voltage, Resistance Drop & Current in a Circuit w/ Zener Diode

In summary: What if you apply a small reverse bias voltage? What if the diode is forward biased? When you learn about Zener diodes you will learn that they have two properties: forward bias and reverse bias. In forward bias the diode is shorted and in reverse bias the diode is open. What is most important to understand is how these two properties change the I-V characteristics of a Zener diode. In forward bias the diode is shorted and the I-V characteristic is like a straight line. When you apply a large reverse bias voltage the diode will start to break down and the I-V characteristic will start to show a curve. This is called the V-I characteristic
  • #1
ranju
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In the given circuit we have to find the output voltage , the voltage drop across resistance RL (RL = 10KΩ) and the current through the zener diode having zener voltage VZ = 50V

By this question I want to be clear about the way to solve circuits with zener diode...please explain the reasoning.. I have studied that in forward bias , zener diode is shorted..in reverse it is open.. but how to apply it... please explain somewahat in this problem..!:confused:
 

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  • #2
ranju said:
In the given circuit we have to find the output voltage , the voltage drop across resistance RL (RL = 10KΩ) and the current through the zener diode having zener voltage VZ = 50V

By this question I want to be clear about the way to solve circuits with zener diode...please explain the reasoning.. I have studied that in forward bias , zener diode is shorted..in reverse it is open.. but how to apply it... please explain somewahat in this problem..!:confused:

No, in reverse bias a Zener diode is not open. Can you show us the V-I characteristic curve of a typical Zener diode? When you read about Zener diodes on wikipedia.org, what does it say? How does avalanche breakdown come into play?
 
  • #3
See first of all I would like you to give me the way how you would solve the circuit I gave...so that I can be somewhat clear...
 
  • #4
ranju said:
See first of all I would like you to give me the way how you would solve the circuit I gave...so that I can be somewhat clear...

No, that's not how the PF works. We require that you show some effort of your own, before we can provide tutorial help. Especially since the wikipedia entry is fairly clear and instructive.

Please read that article, and see if you can answer your question yourself. Post your work on the solution, and ask specific questions if you still have them.
 
  • #5
bur what I want to be clear about is not there in wikipedia..I am familiar with that theory but not getting how to apply...! here the diode is in reverse bias..but how to move on further...
I am actually not getting this thing.. I really need your help..
 
  • #6
ranju said:
bur what I want to be clear about is not there in wikipedia..I am familiar with that theory but not getting how to apply...! here the diode is in reverse bias..but how to move on further...
I am actually not getting this thing.. I really need your help..

What are you not understanding about the V-I characteristic of a Zener diode? What do those curves look like? How can you use that curve to determine the voltages and currents in the circuit that you drew?
 
  • #7
What berkman said.

You need to look at and understand the I-V characteristics of a Zener diode.

When you first learn about diodes you are usually taught that a forward biased diode is like a short circuit and a reverse biased diode is like an open circuit. However that is a very simplistic model. You now need to learn about more accurate models.

For example what happens if you apply a large reverse bias voltage? Does a reverse biased diode always behave like an open circuit?
 

FAQ: Finding Output Voltage, Resistance Drop & Current in a Circuit w/ Zener Diode

What is a Zener diode and how does it work?

A Zener diode is a type of semiconductor device that allows current to flow in the reverse direction when a certain voltage threshold is reached. This voltage threshold, known as the Zener voltage, is determined by the doping level of the diode. When the Zener diode is reverse biased, it acts as a voltage regulator, maintaining a constant voltage across its terminals.

How do I calculate the output voltage of a circuit with a Zener diode?

To calculate the output voltage of a circuit with a Zener diode, you will need to know the input voltage, the Zener voltage, and the load resistance. The output voltage can be calculated using the formula Vout = Vin - Vz, where Vin is the input voltage and Vz is the Zener voltage. It is important to note that the output voltage will be regulated to the Zener voltage as long as the input voltage is greater than the Zener voltage.

How do I calculate the resistance drop across a Zener diode?

The resistance drop across a Zener diode can be calculated using Ohm's law, which states that resistance (R) is equal to voltage (V) divided by current (I). In this case, the voltage (V) would be the difference between the input voltage and the Zener voltage, and the current (I) would be the total current flowing through the circuit.

What is the current flowing through a Zener diode in a circuit?

The current flowing through a Zener diode in a circuit can be calculated using Ohm's law. In this case, the voltage (V) would be the difference between the input voltage and the Zener voltage, and the resistance (R) would be the load resistance in the circuit. It is important to note that the current flowing through the Zener diode will depend on the load resistance and the Zener voltage.

How does the load resistance affect the output voltage and current in a circuit with a Zener diode?

The load resistance plays a crucial role in determining the output voltage and current in a circuit with a Zener diode. A higher load resistance will result in a larger voltage drop across the Zener diode, leading to a lower output voltage and a higher current. On the other hand, a lower load resistance will result in a smaller voltage drop and a higher output voltage, but a lower current. It is important to choose the appropriate load resistance to ensure the Zener diode operates within its specified parameters.

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