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Collector-Base Capacitance Formula

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Collector Base Capacitance is simply the capacitance of the collector-base junction including both the flat bottom portion of the junction and the sidewalls. Check FAQs

C cb = A \cdot \sqrt{\frac{q \cdot ε \cdot N b}{2 \cdot (ψ o + V rb)}}

C_cb - Collector Base Capacitance?A - Emitter Base Junction Area?q - Charge?ε - Permittivity?N_b - Doping Density?ψ_o - Built In Potential?V_rb - Reverse Bias Junction?

Collector-Base Capacitance Example

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With units

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Here is how the Collector-Base Capacitance equation looks like with Values.

Here is how the Collector-Base Capacitance equation looks like with Units.

Here is how the Collector-Base Capacitance equation looks like.

138.6693 = 1.75 \cdot \sqrt{\frac{5 \cdot 71 \cdot 26}{2 \cdot (4.8 + 2.55)}}

138.6693μF = 1.75cm² \cdot \sqrt{\frac{5mC \cdot 71F/m \cdot 26electrons/m³}{2 \cdot (4.8V + 2.55A)}}

138.6693 = 1.75 \cdot \sqrt{\frac{5 \cdot 71 \cdot 26}{2 \cdot (4.8 + 2.55)}}

Tip: Use pencil () icon above to edit Input Values and Units.

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Collector-Base Capacitance Solution

Follow our step by step solution on how to calculate Collector-Base Capacitance?

FIRST Step Consider the formula

C cb = A \cdot \sqrt{\frac{q \cdot ε \cdot N b}{2 \cdot (ψ o + V rb)}}

Next Step Substitute values of Variables

∴

C cb = 1.75cm² \cdot \sqrt{\frac{5mC \cdot 71F/m \cdot 26electrons/m³}{2 \cdot (4.8V + 2.55A)}}

Next Step Convert Units

∴

C cb = 0.0002m² \cdot \sqrt{\frac{0.005C \cdot 71F/m \cdot 26electrons/m³}{2 \cdot (4.8V + 2.55A)}}

Next Step Prepare to Evaluate

∴

C cb = 0.0002 \cdot \sqrt{\frac{0.005 \cdot 71 \cdot 26}{2 \cdot (4.8 + 2.55)}}

Next Step Evaluate

∴

C cb = 0.000138669270808881F

Next Step Convert to Output's Unit

∴

C cb = 138.669270808881μF

LAST Step Rounding Answer

∴

C cb = 138.6693μF

Collector-Base Capacitance Formula Elements

Variables

Functions

Collector Base Capacitance

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

Symbol: C_cb

Measurement: CapacitanceUnit: μF

Note: Value should be greater than 0.

Emitter Base Junction Area

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.

Symbol: A

Measurement: AreaUnit: cm²

Note: Value should be greater than 0.

Charge

Charge a characteristic of a unit of matter that expresses the extent to which it has more or fewer electrons than protons.

Symbol: q

Measurement: Electric ChargeUnit: mC

Note: Value should be greater than 0.

Permittivity

Permittivity is a physical property that describes how much resistance a material offers to the formation of an electric field within it.

Symbol: ε

Measurement: PermittivityUnit: F/m

Note: Value should be greater than 0.

Doping Density

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.

Symbol: N_b

Measurement: Electron DensityUnit: electrons/m³

Note: Value should be greater than 0.

Built In Potential

The Built In Potential affects the size of the depletion region, which in turn influences the capacitance of the junction.

Symbol: ψ_o

Measurement: Electric PotentialUnit: V

Note: Value should be greater than 0.

Reverse Bias 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.

Symbol: V_rb

Measurement: Electric CurrentUnit: A

Note: Value should be greater than 0.

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.

Syntax: sqrt(Number)

Credits

Creator Image

Created by Rahul Gupta

Chandigarh University (CU), Mohali, Punjab

Rahul Gupta has created this Formula and 25+ more formulas!

Verifier Image

Verified by Parminder Singh

Chandigarh University (CU), Punjab

Parminder Singh has verified this Formula and 500+ more formulas!

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How to Evaluate Collector-Base Capacitance?

Collector-Base Capacitance evaluator uses Collector Base Capacitance = Emitter Base Junction Area*sqrt((Charge*Permittivity*Doping Density)/(2*(Built In Potential+Reverse Bias Junction))) to evaluate 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 evaluate Collector-Base Capacitance using this online evaluator? To use this online evaluator 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.

FAQs on Collector-Base Capacitance

What is the formula to find Collector-Base Capacitance?

The formula of Collector-Base Capacitance is expressed as Collector Base Capacitance = Emitter Base Junction Area*sqrt((Charge*Permittivity*Doping Density)/(2*(Built In Potential+Reverse Bias Junction))). Here is an example- 1.4E+8 = 0.000175*sqrt((0.005*71*26)/(2*(4.8+2.55))).

How to calculate Collector-Base Capacitance?

With Emitter Base Junction Area (A), Charge (q), Permittivity (ε), Doping Density (N_b), Built In Potential (ψ_o) & Reverse Bias Junction (V_rb) we can find Collector-Base Capacitance using the formula - Collector Base Capacitance = Emitter Base Junction Area*sqrt((Charge*Permittivity*Doping Density)/(2*(Built In Potential+Reverse Bias Junction))). This formula also uses Square Root (sqrt) function(s).

Can the Collector-Base Capacitance be negative?

No, the Collector-Base Capacitance, measured in Capacitance cannot be negative.

Which unit is used to measure Collector-Base Capacitance?

Collector-Base Capacitance is usually measured using the Microfarad[μF] for Capacitance. Farad[μF], Kilofarad[μF], Millifarad[μF] are the few other units in which Collector-Base Capacitance can be measured.

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