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Several Announcements and another Qucs Video.

Qucs video Part 5

This post is an announcement of several things. As usual I am going to change direction for awhile for several reasons. First the Big Announcement. Create-and-make is the featured website for this week on an outstanding Website for the Electrical Engineering Community, EEWeb.com, A link to the feature and the

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Qucs – Documentation, the Net List, and the Component Library

Title screen of the new video.

I hope by now I have many of you interested in using Qucs for simulating electronics circuits. This is another blog wrapped around a video I have posted. I still do have my “love – hate” relationship with simulations. You can do a lot very quickly with simulations,

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Using Qucs with a Non-linear Model of a Transistor.

The opening screen to the new video.

Tonight I posted a new video. The video shows how to find the parameter values for a non-linear model of the transistor. This is the best possible model. However, remember it is just a model and there is significant manufacturing tolerances in transistors. The simple model we

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Bipolar Junction Transistor DC Biasing Calculations Example.

The model of the circuit we are biasing.

It is Number Crunching Time! Tonight we set the DC Bias of the circuit shown in the first diagram. Once we do that we will run several Qucs simulations of the circuit with the numbers we calculate. We will do those simulations with different values for

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Negative Feedback to compensate for Beta Variation in BJTs.

Negative FB Biasing.

In the last post, “Using the Transistor Model – Our first circuit“, the wide tolerance of β (hFE) in the transistor specifications is making life complicated. “Complicate our life will ya!” We will fix the problem by complicating the circuit to reduce the complications. Seriously, we will add several more resistors

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Using the Transistor D.C. Model – Our first circuit.

The first circuit we will analyse.

In the post “The Basic DC Model for a NPN Bipolar Junction Transistor” we came up with a generic model for a transistor and in the last post “Reading a Datasheet for our DC Transistor Model Parameters” we assigned values to the parts of the model based on

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Reading a Datasheet for our DC Transistor model parameters.

The model for the active region

We have created the form of our DC model for our transistor in the last post, “The Basic DC Model for a NPN Transistor“. However, there are lots of unknown values that we need to determine to build a model for the actual transistor we are going to

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The Basic DC model for an NPN Bipolar Junction Transistor

Modified Current Definitions for our NPN Transistor Model Discussion

There are two ways to create a model. One method is to know how the pieces are parts inside the device operate and use these principles to add all the pieces and parts and their interactions together to develop a “white box” model. The opposite

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Circuit simulation software – Qucs

A Simple model in Qucs

I spent a fairly large about of time trying to find some simulation software to meet the needs of this blog and the readers of this blog. Some of the criteria I used in the search were:

Free or very low cost: Most of us do not have hundreds

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Thevenin and Norton equivalent sources.

Thevenin equivalent source.

Now that we have talked a little about ideal sources it is time to get real. Yeah, I really do mean that. We are going to talk a little about real sources and modelling those. The first one I am going to talk about is the Thevenin model shown in the

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