Simulations play an essential role in any design activity, from simple electronic circuit design to complex aerodynamic simulations. Simulations imitate real-world procedures in a controlled environment. This gives designers the freedom to experiment with different scenarios or combinations of the variables that control the system.

For electronic engineers, there are different simulation tools that you can use to study the behavior of your circuits. You can use SPICE, iCircuit, PartSim, Circuit Lab, NG Spice, GNUCap, Proteus, LT Spice or NI Multisim. But in this tutorial, I will show you a step-by-step guide of how you can perform circuit simulation using NI Multisim.

We will go through the circuit design processes such as schematic capture and simulation. At the end of this tutorial, you will have a standard emitter transistor amplifier configuration that gives an inversion of 180° between the input and output signals.

NI Multisim

Multisim is a robust circuit design and simulation tool suite that uses SPICE to simulate analog and digital circuits. In Multisim, you will find powerful tools such as a built-in oscilloscope, logic analyzer, multimeter, function generator, frequency counter, and logic analyzer, to mention a few. You have virtual access to any instrument that you can find in a small laboratory.

Besides performing simulations, you can design your circuits and perform all the processes that you can do in an EDA/ECAD tool. How cool is that!

Multisim User Interface

Basic Multisim User Interface

The Multisim UI consists of toolbars, a design toolbox, and a circuit window, all placed for your convenience. The program’s toolbar contains buttons for regular functions, while the instruments toolbar contains buttons for each device available on your Multisim.

Common Emitter Amplifier

You will build a BJT Common Emitter Amplifier in the following sections, as shown in the diagram below. This type of amplifier is quite common in electronics, and I thought it might be a good idea to simulate and study its behavior.

You will find this configuration in many circuits, such as audio amplifiers, basic switches for digital circuits, and analog amplifiers. Therefore, this is one of the many basic transistor configurations in electronics.

Schematic Capture

To get started with our simulation, launch Multisim and a circuit window will open on the workspace. We are now ready to place our components.

Always remember to save your file, then complete the following steps to create your circuit.

  1. Select “Place” on the toolbar then click on “Component”. This will take you to the “Select a Component” dialog box.

2. Make sure you select the “Master Database.”

3. Under Group, select “Basic” and then RESISTOR component family. This will display all the resistors in that family.

4. Next, select the resistor value you want from the list and click “OK.”

5. We need five resistors for our amplifier circuit. So, repeat steps 2-4 and place the following resistors randomly: 100 ohms, 3 kohm, 16 kohm, 1 kohm, and 200-ohm resistors.

6. Repeat steps 2-4 above but select the CAPACITOR family instead. Select the following capacitors: 2uF, 300uF, and 800nF.

7. For power, select the Sources group and choose the SIGNAL_VOLTAGE_SOURCES family. Select AC_VOLTAGE and click OK. Make sure the signal source you select has the following attributes: voltage peak-peak and frequency.

8. Finally, under the Sources group, select the POWER_SOURCES family and choose VCC and GROUND.

That’s it! We are now ready to wire up our circuit.

For simplicity’s sake, arrange the components as shown in the diagram below, rotating as needed.

Simulation

This is what we have been waiting for.

Here, we will simulate the design and view the results on a virtual oscilloscope. To set up the tools, click “Simulate” on the toolbar and then select “Instruments.” On the list that appears, choose “Oscilloscope” and place it anywhere on the design window. Next, we will connect the circuit’s input to channel A of the oscilloscope and connect the output to channel B, as shown in the diagram above. Finally, click on the “Run” button to begin the simulation .

If everything has been set up correctly, you should get the following message:

—— Checking SPICE netlist for Simulation1 – Wednesday, 11 August 2021, 3:09:41 PM ——
======= SPICE Netlist check completed, 0 error(s), 0 warning(s) =======

Output

Double click on the oscilloscope, and you will see the following traces:

Finally, adjust the voltage and time base of the oscilloscope until your waveforms are visible and distinguishable. Here, I have set the input waveform (red – channel A) to 10mV/Div and the output waveform (blue – channel B) to 200mV/Div.

Congratulations! You have completed a straightforward circuit simulation using a basic oscilloscope. In this tutorial, you discovered how to develop a simple transistor amplifier circuit and visualize its input and output waveforms. Specifically, you learned:

  • How to build a BJT Common Emitter Amplifier
  • How to simulate in Multisim
  • How to view the waveforms on a virtual oscilloscope