Collector-Base Capacitance Calculator

✖Emitter Base Junction Area is a P-N junction formed between the heavily doped P-type material (emitter) and the lightly doped N-type material (base) of the transistor.ⓘ Emitter Base Junction Area [A]			+10% -10%
✖Charge a characteristic of a unit of matter that expresses the extent to which it has more or fewer electrons than protons.ⓘ Charge [q]			+10% -10%
✖Permittivity is a physical property that describes how much resistance a material offers to the formation of an electric field within it.ⓘ Permittivity [ε]			+10% -10%
✖Doping Density is a process in which certain impurity atoms, such as phosphorus or boron, are introduced into the semiconductor to alter its electrical properties.ⓘ Doping Density [N_b]			+10% -10%
✖The Built In Potential affects the size of the depletion region, which in turn influences the capacitance of the junction.ⓘ Built In Potential [ψ_o]			+10% -10%
✖Reverse Bias Junction refers to the condition in a semiconductor device, where the voltage applied across the junction opposes the normal flow of current through the device.ⓘ Reverse Bias Junction [V_rb]			+10% -10%

✖Collector Base Capacitance is simply the capacitance of the collector-base junction including both the flat bottom portion of the junction and the sidewalls.ⓘ Collector-Base Capacitance [C_cb]

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Formula

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Collector-Base Capacitance

Formula

`"C"_{"cb"} = "A"*sqrt(("q"*"ε"*"N"_{"b"})/(2*("ψ"_{"o"}+"V"_{"rb"})))`

Example

`"138.6693μF"="1.75cm²"*sqrt(("5mC"*"71F/m"*"26electrons/m³")/(2*("4.8V"+"2.55A")))`

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Collector-Base Capacitance Solution

STEP 0: Pre-Calculation Summary

Formula Used

Collector Base Capacitance = Emitter Base Junction Area*sqrt((Charge*Permittivity*Doping Density)/(2*(Built In Potential+Reverse Bias Junction)))
C_cb = A*sqrt((q*ε*N_b)/(2*(ψ_o+V_rb)))
This formula uses 1 Functions, 7 Variables

Functions Used

sqrt - A square root function is a function that takes a non-negative number as an input and returns the square root of the given input number., sqrt(Number)

Variables Used

Collector Base Capacitance - (Measured in Farad) - Collector Base Capacitance is simply the capacitance of the collector-base junction including both the flat bottom portion of the junction and the sidewalls.
Emitter Base Junction Area - (Measured in Square Meter) - Emitter Base Junction Area is a P-N junction formed between the heavily doped P-type material (emitter) and the lightly doped N-type material (base) of the transistor.
Charge - (Measured in Coulomb) - Charge a characteristic of a unit of matter that expresses the extent to which it has more or fewer electrons than protons.
Permittivity - (Measured in Farad per Meter) - Permittivity is a physical property that describes how much resistance a material offers to the formation of an electric field within it.
Doping Density - (Measured in Electrons per Cubic Meter) - Doping Density is a process in which certain impurity atoms, such as phosphorus or boron, are introduced into the semiconductor to alter its electrical properties.
Built In Potential - (Measured in Volt) - The Built In Potential affects the size of the depletion region, which in turn influences the capacitance of the junction.
Reverse Bias Junction - (Measured in Ampere) - Reverse Bias Junction refers to the condition in a semiconductor device, where the voltage applied across the junction opposes the normal flow of current through the device.

STEP 1: Convert Input(s) to Base Unit

Emitter Base Junction Area: 1.75 Square Centimeter --> 0.000175 Square Meter (Check conversion here)
Charge: 5 Millicoulomb --> 0.005 Coulomb (Check conversion here)
Permittivity: 71 Farad per Meter --> 71 Farad per Meter No Conversion Required
Doping Density: 26 Electrons per Cubic Meter --> 26 Electrons per Cubic Meter No Conversion Required
Built In Potential: 4.8 Volt --> 4.8 Volt No Conversion Required
Reverse Bias Junction: 2.55 Ampere --> 2.55 Ampere No Conversion Required

STEP 2: Evaluate Formula

Substituting Input Values in Formula

C_cb = A*sqrt((q*ε*N_b)/(2*(ψ_o+V_rb))) --> 0.000175*sqrt((0.005*71*26)/(2*(4.8+2.55)))

Evaluating ... ...

C_cb = 0.000138669270808881

STEP 3: Convert Result to Output's Unit

0.000138669270808881 Farad -->138.669270808881 Microfarad (Check conversion here)

FINAL ANSWER

138.669270808881 ≈ 138.6693 Microfarad <-- Collector 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 » Collector-Base Capacitance

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Created by Rahul Gupta

Chandigarh University (CU), Mohali, Punjab

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Verified by Parminder Singh

Chandigarh University (CU), Punjab

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< 11 Internal Capacitive Effects and High Frequency Model Calculators

Collector-Base Capacitance

Go Collector Base Capacitance = Emitter Base Junction Area*sqrt((Charge*Permittivity*Doping Density)/(2*(Built In Potential+Reverse Bias Junction)))

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

Collector-Base Capacitance Formula

Collector Base Capacitance = Emitter Base Junction Area*sqrt((Charge*Permittivity*Doping Density)/(2*(Built In Potential+Reverse Bias Junction)))
C_cb = A*sqrt((q*ε*N_b)/(2*(ψ_o+V_rb)))

How Does Collector-Base Capacitance Affect Transistor Performance?

The capacitance between the collector and base has implications for the transistor's high-frequency performance. It can slow down the transistor's response time at higher frequencies because it acts as a coupling or energy storage element. Manufacturers and circuit designers must consider this capacitance when operating BJTs in high-frequency circuits to ensure proper performance.

How to Calculate Collector-Base Capacitance?

Collector-Base Capacitance calculator uses Collector Base Capacitance = Emitter Base Junction Area*sqrt((Charge*Permittivity*Doping Density)/(2*(Built In Potential+Reverse Bias Junction))) to calculate the Collector Base Capacitance, The Collector-Base Capacitance formula is defined in a bipolar junction transistor (BJT) refers to the capacitance between the collector and the base terminals of the transistor. This capacitance arises due to the depletion region and the charge storage within the transistor. Collector Base Capacitance is denoted by C_cb symbol.

How to calculate Collector-Base Capacitance using this online calculator? To use this online calculator for Collector-Base Capacitance, enter Emitter Base Junction Area (A), Charge (q), Permittivity (ε), Doping Density (N_b), Built In Potential (ψ_o) & Reverse Bias Junction (V_rb) and hit the calculate button. Here is how the Collector-Base Capacitance calculation can be explained with given input values -> 1.4E+8 = 0.000175*sqrt((0.005*71*26)/(2*(4.8+2.55))).

FAQ

What is Collector-Base Capacitance?

The Collector-Base Capacitance formula is defined in a bipolar junction transistor (BJT) refers to the capacitance between the collector and the base terminals of the transistor. This capacitance arises due to the depletion region and the charge storage within the transistor and is represented as C_cb = A*sqrt((q*ε*N_b)/(2*(ψ_o+V_rb))) or Collector Base Capacitance = Emitter Base Junction Area*sqrt((Charge*Permittivity*Doping Density)/(2*(Built In Potential+Reverse Bias Junction))). Emitter Base Junction Area is a P-N junction formed between the heavily doped P-type material (emitter) and the lightly doped N-type material (base) of the transistor, Charge a characteristic of a unit of matter that expresses the extent to which it has more or fewer electrons than protons, Permittivity is a physical property that describes how much resistance a material offers to the formation of an electric field within it, Doping Density is a process in which certain impurity atoms, such as phosphorus or boron, are introduced into the semiconductor to alter its electrical properties, The Built In Potential affects the size of the depletion region, which in turn influences the capacitance of the junction & Reverse Bias Junction refers to the condition in a semiconductor device, where the voltage applied across the junction opposes the normal flow of current through the device.

How to calculate Collector-Base Capacitance?

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