# How to draw diode characteristics using LtSpice

#### Draw diode characteristics

A diode is a specialized electronic component with two electrodes called the anode and the cathode. Most diodes are made with semiconductor materials such as silicon, germanium, or selenium. Diodes can be used as rectifiers, signal limiters, voltage regulators, switches, signal modulators, signal mixers, signal De-modulators, and oscillators.

The fundamental property of a diode is its tendency to conduct electric current in only one direction. When the cathode is negatively charged relative to the anode at a voltage greater than a certain minimum called forward break over, then current flows through the diode. If the cathode is positive with respect to the anode, is at the same voltage as the anode, or is negative by an amount less than the forward break over voltage, then the diode does not conduct current. The forward break over voltage is approximately six-tenths of a volt (0.6 V) for silicon devices, 0.3 V for germanium devices, and 1 V for selenium devices.

#### What are the characteristics of Diode

PN junction diode is symbolically represented as shown in the figure. The direction of the arrow is the direction of conventional current flow (under forward bias. The process of applying an external voltage is called as “biasing”. There are two ways in which we can bias a PN junction diode.

1.Forward Bias

2.Reverse Bias

#### Forward Bias

Forward biasing a PN junction diode is very simple. You just need to take a battery whose values can be varied from (o to V volts), connect its positive terminal to the p-side of PN junction diode and then connect the negative terminal of the battery to the n-side of the PN junction diode.

Now let’s see how to plot the forward characteristics of a diode using LTSpice. The first step is to draw the circuit diagram. The diagram should have a voltage source (Vext), a diode and a  resistance.

Drawing the circuit

Draw a voltage source – Open LTspice and select the new schematic button to draw a new circuit.
Click on the component symbol and select a voltage source (for details description refer …..). place it in the required position. See the below screenshot.

Add a resistor to the diagram by selecting and dragging it to the required position.

Now we need to join the components together to build a circuit. Select the wire component from the top menu and join the components. Don’t forget to add a ground to your circuit.

Next step is to specify values for your components. Right-click on the resistance and provide the required values. In our experiment let’s take it as 1k.

Now pick the diode by right-clicking on the diode symbol. Select the option “pick new diode” and select the required diode from the pop-up list.

Now the final step to select your voltage source. Let’s applying 1vDC. Refer the below screenshot.

Now finally we need to run our circuit to see the output. In order to do this, we need to click on the run button on the top menu. Select the “DC sweep tab from the popup menu. Now provide the required values

1. Voltage source V1 –
2. Type of sweep – linear
3. Start value =0
4. Stop value = 1
5. Increment- 5 Millivolt.

Click OK button.

Now you will have a screen with two windows. One is a graph and the other is a circuit.

We need to plot the characteristics. To find the current, click on the diode symbol.

The final output is as shown above.