Small-Signal Diffusion Capacitance of BJT Calculator

✖A device constant value is defined once and can be referenced many times throughout a program.ⓘ Device Constant [𝛕_F]			+10% -10%
✖Collector current is an amplified output current of a bipolar junction transistor.ⓘ Collector Current [I_c]			+10% -10%
✖Threshold voltage of transistor is the minimum gate to source voltage that is needed to create a conducting path between the source and drain terminals.ⓘ Threshold Voltage [V_th]			+10% -10%

✖Emitter-base capacitance is the capacitance between the emitter and the base.ⓘ Small-Signal Diffusion Capacitance of BJT [C_eb]

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Formula

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Small-Signal Diffusion Capacitance of BJT

Formula

`"C"_{"eb"} = "𝛕"_{"F"}*("I"_{"c"}/"V"_{"th"})`

Example

`"1818.182μF"="2s"*("5mA"/"5.50V")`

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Small-Signal Diffusion Capacitance of BJT Solution

STEP 0: Pre-Calculation Summary

Formula Used

Emitter-Base Capacitance = Device Constant*(Collector Current/Threshold Voltage)
C_eb = 𝛕_F*(I_c/V_th)
This formula uses 4 Variables

Variables Used

Emitter-Base Capacitance - (Measured in Farad) - Emitter-base capacitance is the capacitance between the emitter and the base.
Device Constant - (Measured in Second) - A device constant value is defined once and can be referenced many times throughout a program.
Collector Current - (Measured in Ampere) - Collector current is an amplified output current of a bipolar junction transistor.
Threshold Voltage - (Measured in Volt) - Threshold voltage of transistor is the minimum gate to source voltage that is needed to create a conducting path between the source and drain terminals.

STEP 1: Convert Input(s) to Base Unit

Device Constant: 2 Second --> 2 Second No Conversion Required
Collector Current: 5 Milliampere --> 0.005 Ampere (Check conversion here)
Threshold Voltage: 5.5 Volt --> 5.5 Volt No Conversion Required

STEP 2: Evaluate Formula

Substituting Input Values in Formula

C_eb = 𝛕_F*(I_c/V_th) --> 2*(0.005/5.5)

Evaluating ... ...

C_eb = 0.00181818181818182

STEP 3: Convert Result to Output's Unit

0.00181818181818182 Farad -->1818.18181818182 Microfarad (Check conversion here)

FINAL ANSWER

1818.18181818182 ≈ 1818.182 Microfarad <-- Emitter-Base Capacitance

(Calculation completed in 00.004 seconds)

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Home » Engineering » Electronics » BJT » Analog Electronics » Internal Capacitive Effects and High Frequency Model » Small-Signal Diffusion Capacitance of BJT

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Created by Payal Priya

Birsa Institute of Technology (BIT), Sindri

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Vishwakarma Government Engineering College (VGEC), Ahmedabad

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< 10+ Internal Capacitive Effects and High Frequency Model Calculators

Collector-Base Junction Capacitance

Go Collector-Base Junction Capacitance = Collector-Base Junction Capacitance at 0 Voltage/(1+(Reverse-Bias Voltage/Built-In Voltage))^Grading Coefficient

Transition Frequency of BJT

Go Transition Frequency = Transconductance/(2*pi*(Emitter-Base Capacitance+Collector-Base Junction Capacitance))

Concentration of Electrons Injected from Emitter to Base

Go Concentration of e- Injected from Emitter to Base = Thermal Equilibrium Concentration*e^(Base-Emitter Voltage/Thermal Voltage)

Unity-Gain Bandwidth of BJT

Go Unity-Gain Bandwidth = Transconductance/(Emitter-Base Capacitance+Collector-Base Junction Capacitance)

Small-Signal Diffusion Capacitance of BJT

Go Emitter-Base Capacitance = Device Constant*(Collector Current/Threshold Voltage)

Thermal Equilibrium Concentration of Minority Charge Carrier

Go Thermal Equilibrium Concentration = ((Intrinsic Carrier Density)^2)/Doping Concentration of Base

Small-Signal Diffusion Capacitance

Go Emitter-Base Capacitance = Device Constant*Transconductance

Stored Electron Charge in Base of BJT

Go Stored Electron Charge = Device Constant*Collector Current

Transition Frequency of BJT given Device Constant

Go Transition Frequency = 1/(2*pi*Device Constant)

Base-Emitter Junction Capacitance

Go Base–Emitter Junction Capacitance = 2*Emitter-Base Capacitance

Small-Signal Diffusion Capacitance of BJT Formula

Emitter-Base Capacitance = Device Constant*(Collector Current/Threshold Voltage)
C_eb = 𝛕_F*(I_c/V_th)

What is the difference between transition capacitance and diffusion capacitance?

Transition capacitance is basically the change of charge stored in the depletion region with respect to a change in voltage. And Diffusion capacitance is the capacitance caused due to movement of charge carriers between from anode to cathode in the forward-biased mode.

How to Calculate Small-Signal Diffusion Capacitance of BJT?

Small-Signal Diffusion Capacitance of BJT calculator uses Emitter-Base Capacitance = Device Constant*(Collector Current/Threshold Voltage) to calculate the Emitter-Base Capacitance, The Small-signal diffusion capacitance of BJT formula is defined as capacitance due to transport of charge carriers between two terminals of device, for example, diffusion of carriers from anode to cathode in forward-bias mode of diode or from emitter to base forward-biased junction for transistor. Emitter-Base Capacitance is denoted by C_eb symbol.

How to calculate Small-Signal Diffusion Capacitance of BJT using this online calculator? To use this online calculator for Small-Signal Diffusion Capacitance of BJT, enter Device Constant (𝛕_F), Collector Current (I_c) & Threshold Voltage (V_th) and hit the calculate button. Here is how the Small-Signal Diffusion Capacitance of BJT calculation can be explained with given input values -> 1.8E+9 = 2*(0.005/5.5).

FAQ

What is Small-Signal Diffusion Capacitance of BJT?

The Small-signal diffusion capacitance of BJT formula is defined as capacitance due to transport of charge carriers between two terminals of device, for example, diffusion of carriers from anode to cathode in forward-bias mode of diode or from emitter to base forward-biased junction for transistor and is represented as C_eb = 𝛕_F*(I_c/V_th) or Emitter-Base Capacitance = Device Constant*(Collector Current/Threshold Voltage). A device constant value is defined once and can be referenced many times throughout a program, Collector current is an amplified output current of a bipolar junction transistor & Threshold voltage of transistor is the minimum gate to source voltage that is needed to create a conducting path between the source and drain terminals.

How to calculate Small-Signal Diffusion Capacitance of BJT?

The Small-signal diffusion capacitance of BJT formula is defined as capacitance due to transport of charge carriers between two terminals of device, for example, diffusion of carriers from anode to cathode in forward-bias mode of diode or from emitter to base forward-biased junction for transistor is calculated using Emitter-Base Capacitance = Device Constant*(Collector Current/Threshold Voltage). To calculate Small-Signal Diffusion Capacitance of BJT, you need Device Constant (𝛕_F), Collector Current (I_c) & Threshold Voltage (V_th). With our tool, you need to enter the respective value for Device Constant, Collector Current & Threshold Voltage and hit the calculate button. You can also select the units (if any) for Input(s) and the Output as well.

How many ways are there to calculate Emitter-Base Capacitance?

In this formula, Emitter-Base Capacitance uses Device Constant, Collector Current & Threshold Voltage. We can use 1 other way(s) to calculate the same, which is/are as follows -

Emitter-Base Capacitance = Device Constant*Transconductance

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