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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

Continue reading Negative Feedback to compensate for Beta Variation in BJTs.

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

Continue reading Reading a Datasheet for our DC Transistor model parameters.

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

Continue reading Thevenin and Norton equivalent sources.

Linearity and our pencil and paper models for Electronics.

Independent Sources

Our goal now is to come up with a way to create simple models of electronic circuits. From the discussion last time “Design, Models, and Simulations“, we understand our model will be very simplified and therefore inaccurate. However, it will be good enough for our first shot before going to the trouble

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Field Effect Transistor Theory – Part 3

Depletion Mode IGFET symbols

In part 2 I finished up the description of the JFET. Tonight I will describe the operation of an Insulated Gate Field Effect Transistor (IGFET). Most often an IGFET is called a MOSFET because of the materials used in it, Metal Oxide Silicon FET. For those of you that have

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Field Effect Transistor Theory – Part 2

JFET symbols

In Part 1 we introduced a conceptual diagram of the construction of a JFET and talked about what happens if the gate voltages is changed in comparison to the source while the drain to source voltage is kept at a low value. Today we are going to start out talking about what

Continue reading Field Effect Transistor Theory – Part 2

Theory Vs. Reality: First Comes the Assumpton Then It All Goes to Hell

This is a post where I could think of a lot of very funny names and titles, but when it came down to the actually writing one I chose the term I most often use in professional life. “First comes the Assumption Then It all Goes to Hell”. Very often the calculations and number crunching

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Field Effect Transistor Theory – Part 1

JFET symbols

As we continue to work through the Desulfator circuit we only have one device left that we have yet to talk about and that is the MOSFET. A MOSFET is a type of Field Effect Transistor (FET). Tonight we are going to point the ship toward understanding it, but to understand the

Continue reading Field Effect Transistor Theory – Part 1

Drawing the Schematic for the Desulfator in Kicad.

The Desulfator Schematic in KiCad

HAPPY NEW YEAR! Usually this time of year I think about what I accomplished in the last year and also where I want to go in the next one. I have been so busy this season that I really have not given it as much thought as usual. However,

Continue reading Drawing the Schematic for the Desulfator in Kicad.