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Questions tagged [ebers-moll]

For questions about the Ebers-Moll model for bipolar junction transistors (BJTs). Always use in conjunction with the "bjt" tag.

For questions about the Ebers-Moll model for bipolar junction transistors (BJTs). Always use in conjunction with .

See Wikipedia's section on the Ebers-Moll model for more information.

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What are the limits of the Ebers-Moll model for large currents?

I learned that the Ebers-Moll equation Ic = Is(T) ∗ exp(Vbe/Vt) "predicts" the collector current to rise exponentially with the base-emitter Voltage. Experimenting with LTSpice for a LED current sink I apparently ran into the limits of the…
ChristophK
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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 current. Of course this is not completely true, since…
Tob Ernack
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Early effect in simple current mirror

By "simple current mirror" I mean the following circuit. Due to the Early effect the output current changes to some degree with output voltage. According to The Art of Electronics (3rd edition), this is because of the slight variation of…
apadana
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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?
user1245
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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 inverse saturation current. Finding it from a data sheet…
Enrico
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On the huge error between LTSPICE and Ebers-Moll when vCE=0 for a BJT

Let us assume that we have a npn BJT with parameters similar to 2N2222 in LTSPICE at T=27 C The thermal voltage at T=27C is VT=25.865 mV Let us assume that VCE=0 and VBE=0.85 V From 2N2222 in LTSPICE we have: IS=10^-14 A, VA=100 V, BETA=200,…
Aria
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The small-signal impedance looking into the emitter when base voltage is not fixed

In section 2.3.2 of the 3rd edition of The Art of Electronics, the small-signal impedance looking into the emitter, \$r_\text{e}\$, for the base held at a fixed voltage is defined as "the derivative of \$V_\text{BE}\$ with respect to…
apadana
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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 help extend the functional range. Does similar…
KFW
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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)?
RobertSzili
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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 Saturation Current). Does someone know value of this Is…
Amit
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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 the particular transistor (which depends strongly…
KMC
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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 anything inaccurate in it (yet). This is a large…
SpacemanScott
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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 \$I_B\$ using the formulas given under the…
Zack Frost
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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 someone explain which equation is used in which case? Or is…
Thomas
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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 sure different BJTs (say, 2N2222, 2N3904, BC548,...)…
Victory
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