Difference between revisions of "CircuitJS/C3/Silicon-Diode-Characteristics/English"

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Revision as of 17:11, 24 April 2024

Visual Cue Narration
slide:1 Welcome to the spoken tutorial on Silicon Diode Characteristics using CircuitJS simulator.
Slide 2:

Learning Objective

In this tutorial, we will learn about
  • Voltage-Current(V-I) characteristics of Silicon diode in forward and reverse bias.
Slide 3:

System Requirement

To record this tutorial, I am using:
  • Ubuntu Linux 20.04 OS
  • CircuitJS Application
Slide 4:

Prerequisite

To follow this tutorial, you should have a basic knowledge of
  • Electrical circuits
Slide 5:

What is a Diode?

  • Diode is a semiconductor device with two terminals.
  • These terminals control the flow of electrons in a circuit.
  • Diodes can be used as rectifiers, switches, voltage regulators etc.
Slide 6:

Diode image

Diode_Symbol.png

  • Diode is represented with this symbol.
  • The diode symbol has a triangle with a line across one vertex.
  • The vertex side of the triangle is cathode.
  • The base side of the triangle is an anode of the diode.
Slide:

Diode Biasing

The process of applying an external voltage to a p-n junction of a diode is called biasing.

There are two ways of Biasing:

  1. Forward Bias and
  2. Reverse Bias
Forward Bias

Forward_Bias_Diode.png

In forward bias,
  • The positive terminal of the power supply is connected to the P-Junction or anode of diode
  • The negative terminal of the power supply is connected to the N-junction or cathode of the diode
We will make this circuit to explain forward bias characteristics of the diode.
Show the diagram

Forward_Bias_Diode.png

For Forward bias diode circuit, we require,
  • Variable voltage (That is, 0 volts to 2 volts)
  • Diode
  • Ammeter
  • 1 Ohm resistor
  • Ground
Keep the circuit diagram on top right Let us open the CircuitJS interface.

In the menu bar, click on File and select New Blank Circuit.

Select variable voltage Click on Draw, go to Inputs and Sources, and select Add Variable voltage.

Draw the variable voltage in the working area as shown.

We require a voltage range of 0 to 2 volts.

Right click on the variable voltage component and select the Edit option.

In the Minimum voltage box, enter 0 and in the maximum voltage box, enter 2.

Click on the OK button to save the changes.

Select Diode Click on Draw, go to Active Components, and select Add Diode option.

Draw the diode in the working area.

This is the default diode available on the CircuitJS platform.

This diode has characteristics of a Silicon diode.

Connect the P-junction of the diode to the variable voltage in the circuit.

Select Ammeter Now, click on Draw, go to Outputs and Labels, and select Add Ammeter component.

Draw the ammeter in the working area as shown.

Connect the ammeter to the N-junction of the diode.

Next, we will connect a resistor to the ammeter.

Select Resistor Go to Draw, select Add resistor option.

Drag and draw the resistor in the working area as shown.

The default value of the resistor is 1 Kilo Ohm.

Use the Edit option and change the resistor value to 1 Ohm.

Select Ground Now, we need a ground component to complete the circuit.

Click on Draw, go to Inputs and Sources and select Add ground option.

Draw and connect the ground component to the resistor in the circuit as shown.

Observe the yellow dots indicating the current flow in the circuit.

On the right side, you will see a slider to change the voltage value.

Use the slider to change the variable voltage value to 0 volts as shown.

We need a graph with relevant values of voltage and current.

These values will explain the V-I characteristics of a silicon diode.

Select View in New Scope and open graph

Go to settings

Right click on the diode and select View in New Scope option.

A graph will appear at the bottom of your screen.

Increase the size of the graph by dragging the graph screen.

At the bottom left corner, you will see a Settings icon, click on it.

Change the graph

A pop-window will open.

Click on the X-Y Plot option, and check the Show V vs I box.

Click on the OK button to save the changes.

The voltage values are plotted on the X-axis represented by the green line.

The current values are plotted on the Y-axis represented by the yellow line.

FB_Observation Table.png Create a table to note down the current readings for the given voltage values.
FB_0 volts.png

Silicon_Diode Video.mp4 (do not include from 6.38 to 8.06)

At 0 volts, the ammeter shows no current flowing through the diode.

Hence, the current value for this condition is 0 Ampere.

Notice the dot in the graph, which shows the voltage and current values.

Editing

Put a red box around the changes in values

FB_0.5 volts.png

Now, we will gradually increase the variable voltage using the voltage slider.

Note the changes in voltage and current in the circuit.

For voltage value 0.5 volts, the ammeter shows negligible current flow through the diode.

We can see the dot on the graph moving along the x-axis.

FB_0.7 volts.png As we increase the voltage value to 0.7 volts, the ammeter shows an increase in the current value.

The dot in the graph moves on the Y axis which shows increase in current.

This point where the current increases is called the knee voltage.

Thus, the knee voltage for the silicon diode is 0.7 volts.

Move the slider the slowly

FB_2 volts.png

Note down the current reading for the remaining voltage values of 1 volt, 1.5 volts and 2 volts.

Notice the dot in the graph showing an increase in the current value.

Hence for input voltage above 0.7 volts, the silicon diode acts as a conductor.

Now let us see how a diode behaves in reverse bias mode.
Slide:

Reverse_Bias_Diode.png

In reverse bias,
  1. The positive terminal of the power supply is connected to the N-Junction or cathode of the diode;
  2. The negative terminal of the power supply is connected to the P-junction or anode of the diode;
Reverse_Bias_Diode.png We will create this circuit to explain reverse bias characteristics of the diode.

Go back to CircuitJs simulator.

Let us first set the variable voltage value to 0 volts using the slider.
CircuitJS Explanation Click on the RUN/Stop button on the top right corner to stop the simulation.

Click on the Reset button to erase the forward bias V-I characteristics graph.

Let us change the circuit for Reverse bias mode.

Right click on the diode and select the Swap Terminals option.

The positive end of the supply is now connected to the cathode of the diode.

And the negative end is connected to the anode of the diode.

A reverse bias diode circuit is ready.

Now, start the simulation by clicking on the RUN/Stop button again.

Since voltage is not applied to the circuit, current cannot pass through the circuit.

RB_Observation Table.png

Editing

Red box around the negative value

Let us increase the variable voltage from 0 volts to 2 volts using the slider.

Refer to the observation table for the diode connected in reverse bias mode.

Since the diode is connected in reverse bias, the voltage and current readings will be negative.

Show dot in the graph For all voltage values, the current flowing through the diode is negligible.

Notice the dot on the graph, it moves along the negative x-axis.

This indicates that there is no change in the current flowing through the diode.

Slide:

Diode Characteristics

Thus we can conclude the following;
  1. Forward bias in a diode allows current flow, enabling conduction.
  2. Reverse bias creates a barrier, limiting a negligible current passing through the diode
This brings us to the end of the tutorial. Let us summarize.
Slide Summary In this tutorial, we learnt about
  • Voltage-current(V-I), characteristics of Silicon diode in forward and reverse bias
Slide:

Assignment

As an assignment,
  • Find the knee voltage of the Germanium diode.

Hint - Double click on the diode and select 1N34 (germanium diode).

Slide :

About Spoken Tutorial project

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Acknowledgement Spoken Tutorial project was established by the Ministry of Education(MoE), Govt of India
Thank you This tutorial has been contributed by FOSSEE and Spoken Tutorial Project, IIT Bombay.

Thanks for watching.

Contributors and Content Editors

Madhurig, Nirmala Venkat

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