Questions tagged [ebers-moll]
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14
questions
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1answer
43 views
How do you use an LED's log V/I curve to force an exponential current change in the LED for a linear voltage change?
The info needed to make log and exponential converters with silicon is widely available. The saturation current, intrinsic resistances, and the Ebers-Moll equation are sufficient. A few other numbers ...
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1answer
59 views
Do Ebers-Moll model cover all working modes of BJTs?
I mean the normal working modes (cutoff, forward/reverse active, saturation).
Or an other form of the question: Do Ebers-Moll cover the whole working domain of BJT (in potential and current values)?
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0answers
46 views
What is value of Reverse Saturation Current (Is) for BC547B NPN transistor
I am trying to evaluate Ebers Moll equation for estimating collector current for a given V_BE at DC conditions. The datasheet of BC547B (which I am using) does not mention the Is (i.e. Reverse ...
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2answers
192 views
How to use Ebers-Moll equation to calculate collector current?
The Ebers-Moll equation is given by:$$I_C = I_S(T) * (e^{V_{BE}/V_T})$$
where \$V_T\$ = \$kT/q\$ = 25.3mV at room temperature. In TAOE (2.3.1), it mentioned
\$I_S(T)\$ is the saturation current of ...
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1answer
150 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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1answer
207 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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0answers
161 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
252 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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1answer
2k 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
201 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
377 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 ...
1
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1answer
186 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 ...
1
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1answer
239 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
1k 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 ...
