Let's use LTspice - Check transistor characteristics with DC sweep analysis

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Design Analog Devices

Have you ever tried to use LTspice and installed it, but have been frustrated in the middle of trying to enter while looking at a reference book, or have you not obtained the desired result due to an error?

In order to solve such problems, this time, we will introduce how to perform DC Sweep analysis using a simulation file prepared in advance in a folder called "Educational".

If you are just starting LTspice, we recommend that you look at the "basics" from the list below.

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Also, if you would like to see a video on how to write a basic circuit and how to execute it, there is an on-demand seminar that does not require you to enter personal information. Detailed information about the seminar is also provided to those who fill in the questionnaire.
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Educational folder

In the article "Easy! How to draw a circuit diagram in 5 steps", I introduced how to read a JIG circuit and easily simulate a switching regulator.

This time, we will use the files prepared in the Educational folder.

Open file for DC Sweep analysis

The Educational folder can be opened in the order of My Documents → LTspiceXVII → examples → Educational.

This time, open a file called "curvetrace.asc" from within the Educational folder.

Then I was able to open the schematic for the bipolar transistor 2N222 in Figure 1.
Use this file to check DC Sweep.
DC Sweep simulates device characteristics by changing values in a DC manner.

Figure 1: Voltage value when resistance value is changed

Setting up a DC Sweep analysis

The DC Sweep analysis settings are as follows.
The red underscore in ① is the setting of the voltage V1 between the collector and the emitter.
It means to sweep V1 from 0V to 15V in 10mV steps.
Right clicking on the text will open the Edit Simulation Command (Figure 2).
By selecting 1st Source, you can check the V1 settings.

The blue underlined part in ② is the setting for the current I1 that flows through the base.
It means changing I1 from 20uA to 100uA in 20uA steps.
You can check the setting of I1 by selecting 2nd Source in Edit Simulation Command.

Confirmation of IV curve of transistor 2N222

After executing RUN, you will get an IV curve as shown in Figure 3.
You can use this file and modify it slightly to check the IV characteristics of another transistor.
Also, you can check the IV characteristics of the FET by changing the current source I1 to a voltage source.

In the Educational folder, there are simulation examples other than the DC Sweep analysis introduced this time.
I hope you will make good use of it.

At the end

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