Questions tagged [ebers-moll]

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How to calculate Current Emitter (Ie) using Eber-Molls model on an NPN transistor

my computer science professor gave us a problem to code in python involving Ebers-Moll model for circuits where he asks us to find the current emitter (Ie). In the program we ask the user to give us ...
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87 views

Question on Ebers-Moll model

I have what should be a simple misunderstanding of a piece of text from "RF Circuit Design" by Lugwig. I am not in a class, just self-teaching. This book has been quite helpful, and I have not found ...
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93 views

T Model of a transistor

I want to redraw this circuit based om the T model. Is this T model representation correct? Where Zth is the parallel between R1 and R2 in series with C1, re = (Vt/Ie) Vt being the early voltage, Z2 ...
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98 views

Transistor current source \beta varies (AoE Ex. 2.23)

I am having trouble solving the following exercise: Exercise: If \$ \beta \$ varies from 50 to 100 for collector voltages within the output compliance range, how much will the output current vary? (...
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81 views

What part of Ebers-Moll equation shows the decrease of the collector current in saturation region

By looking at the Ebers-Moll equation for a BJT transistor: Is this formula explicitly showing why Ic starting to decrease towards zero in saturation region. Which part of the equation shows that?
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109 views

Reverse biased diode formula in Ebers-Moll model

As far as I understand in an PNP transistor the base voltage Vb is higher potential than the collector voltage. So since Vb>Vc the base collector junction is then reverse biased: But in Ebers-Moll ...
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1answer
196 views

Operation of BJT with low values of Vbe (“cutoff” region)

Many sources claim that when the base-emitter voltage becomes smaller than approximately 0.6V-0.7V, the bipolar junction transistor goes in the cutoff region and there is zero base and collector ...
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1k views

Saturation current in Ebers-Moll equations for BJT: what is it and how to measure it?

In Ebers-Moll Equations for common emitter BJT the inverse saturation current \$I_s\$ appears as a parameter. What is the saturation current \$I_s\$ exactly and how should I measure in a common ...
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2answers
170 views

Ebers–Moll model aF? Where does it come from?

I am just getting back into electronics after a long while. For the life of me I can't figure where the \$\alpha_F\$ variable in the Ebers–Moll model comes from when you are calculating \$I_C\$ or \$...
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1answer
260 views

An NPN BJT - from Spice to Ebers-Moll

Wikipedia reports a simple model for a BJT in active mode (an approximation to the Ebers-Moll model): \$I_E=-I_{ES}(e^{V_{BE}/V_T}-1)\$ (in the NPN case). Here, \$I_{ES}\$ is the Base-Emitter ...
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162 views

Which equation of the Ebers-Moll-Model is correct?

I'm confused. In different sources sometimes I find the equation \$ I_C = I_S\cdot\left(e^{\frac{U_{BE}}{U_T}}-1\right) \$ or like wikipedia \$ I_C = I_S\cdot e^{\frac{U_{BE}}{U_T}} \$ Can ...
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169 views

Collector currents of different BJT Models and Ebers-Moll

Per Horowitz&Hill book, the Ebers-Moll equation for the collector current in a BJT is: Ic = Is (e ^ (Vbe/Vt) - 1) where Ic is the collector current and Is is the saturation current. Now, I am ...
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5answers
860 views

Can you find an analytic expression for the (beta)hfe of a BJT?

I understand there are two models \$Ic=\beta Ib\$ and \$Ic=I_s exp (\frac{V_{BE}}{Vt})\$ for a bipolar junction transistor. However (correct me if I am wrong), I have not seen any textbook ...