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Common Mode Rejection Ratio of BJT Formula

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Common Mode Rejection Ratio indicates how much of the common-mode signal will appear in your measurement. Check FAQs

CMRR = \frac{2 \cdot G m \cdot R o}{\frac{ΔR c}{R c}}

CMRR - Common Mode Rejection Ratio?G_m - Transconductance?R_o - Output Resistance?ΔR_c - Change in Collector Resistance?R_c - Collector Resistance?

Common Mode Rejection Ratio of BJT Example

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Here is how the Common Mode Rejection Ratio of BJT equation looks like with Values.

Here is how the Common Mode Rejection Ratio of BJT equation looks like with Units.

Here is how the Common Mode Rejection Ratio of BJT equation looks like.

11.395 = \frac{2 \cdot 1.72 \cdot 2.12}{\frac{2.4}{3.75}}

11.395dB = \frac{2 \cdot 1.72mS \cdot 2.12kΩ}{\frac{2.4kΩ}{3.75kΩ}}

11.395 = \frac{2 \cdot 1.72 \cdot 2.12}{\frac{2.4}{3.75}}

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Common Mode Rejection Ratio of BJT Solution

Follow our step by step solution on how to calculate Common Mode Rejection Ratio of BJT?

FIRST Step Consider the formula

CMRR = \frac{2 \cdot G m \cdot R o}{\frac{ΔR c}{R c}}

Next Step Substitute values of Variables

∴

CMRR = \frac{2 \cdot 1.72mS \cdot 2.12kΩ}{\frac{2.4kΩ}{3.75kΩ}}

Next Step Convert Units

∴

CMRR = \frac{2 \cdot 0.0017S \cdot 2120Ω}{\frac{2400Ω}{3750Ω}}

Next Step Prepare to Evaluate

∴

CMRR = \frac{2 \cdot 0.0017 \cdot 2120}{\frac{2400}{3750}}

LAST Step Evaluate

∴

CMRR = 11.395dB

Common Mode Rejection Ratio of BJT Formula Elements

Variables

Common Mode Rejection Ratio

Common Mode Rejection Ratio indicates how much of the common-mode signal will appear in your measurement.

Symbol: CMRR

Measurement: NoiseUnit: dB

Note: Value can be positive or negative.

Formulas to find Common Mode Rejection Ratio

Transconductance

Transconductance is the ratio of the change in current at the output terminal to the change in the voltage at the input terminal of an active device.

Symbol: G_m

Measurement: Electric ConductanceUnit: mS

Note: Value can be positive or negative.

Formulas to find Transconductance

Output Resistance

Output resistance is the value of resistance of the network.

Symbol: R_o

Measurement: Electric ResistanceUnit: kΩ

Note: Value can be positive or negative.

Formulas to find Output Resistance

Change in Collector Resistance

Change in collector resistance is the increment or decrement in resistance passing through the collector region.

Symbol: ΔR_c

Measurement: Electric ResistanceUnit: kΩ

Note: Value can be positive or negative.

Formulas to find Change in Collector Resistance

Collector Resistance

Collector Resistance (Rc)helps to set the transistor at the "operating point" of the amplifier. The purpose of the emitter resistor Re is to prevent "thermal runaway".

Symbol: R_c

Measurement: Electric ResistanceUnit: kΩ

Note: Value can be positive or negative.

Formulas to find Collector Resistance

Other Formulas to find Common Mode Rejection Ratio

Go Common Mode Rejection Ratio

CMRR = 20 \cdot \log 10 (\frac{A d}{A cm})

Other formulas in Common Mode Rejection Ratio (CMRR) category

Go Common Mode Input Resistance of BJT Half-Circuit

R in = (β \cdot R o) \cdot (\frac{1 + (\frac{R L}{β \cdot R o})}{1 + (\frac{R L + (2 \cdot R o)}{R o})})

How to Evaluate Common Mode Rejection Ratio of BJT?

Common Mode Rejection Ratio of BJT evaluator uses Common Mode Rejection Ratio = (2*Transconductance*Output Resistance)/(Change in Collector Resistance/Collector Resistance) to evaluate the Common Mode Rejection Ratio, The Common mode rejection ratio of BJT formula is defined as a metric used to quantify the ability of the device to reject common-mode signals, i.e. those that appear simultaneously and in-phase on both inputs. Common Mode Rejection Ratio is denoted by CMRR symbol.

How to evaluate Common Mode Rejection Ratio of BJT using this online evaluator? To use this online evaluator for Common Mode Rejection Ratio of BJT, enter Transconductance (G_m), Output Resistance (R_o), Change in Collector Resistance (ΔR_c) & Collector Resistance (R_c) and hit the calculate button.

FAQs on Common Mode Rejection Ratio of BJT

What is the formula to find Common Mode Rejection Ratio of BJT?

The formula of Common Mode Rejection Ratio of BJT is expressed as Common Mode Rejection Ratio = (2*Transconductance*Output Resistance)/(Change in Collector Resistance/Collector Resistance). Here is an example- 11.395 = (2*0.00172*2120)/(2400/3750).

How to calculate Common Mode Rejection Ratio of BJT?

With Transconductance (G_m), Output Resistance (R_o), Change in Collector Resistance (ΔR_c) & Collector Resistance (R_c) we can find Common Mode Rejection Ratio of BJT using the formula - Common Mode Rejection Ratio = (2*Transconductance*Output Resistance)/(Change in Collector Resistance/Collector Resistance).

What are the other ways to Calculate Common Mode Rejection Ratio?

Here are the different ways to Calculate Common Mode Rejection Ratio-

Common Mode Rejection Ratio=20*log10(Differential Mode Gain/Common Mode Gain)

Can the Common Mode Rejection Ratio of BJT be negative?

Yes, the Common Mode Rejection Ratio of BJT, measured in Noise can be negative.

Which unit is used to measure Common Mode Rejection Ratio of BJT?

Common Mode Rejection Ratio of BJT is usually measured using the Decibel[dB] for Noise. Neper[dB], MilliDecibel[dB] are the few other units in which Common Mode Rejection Ratio of BJT can be measured.

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Common Mode Rejection Ratio of BJT Formula

​GoCommon Mode Rejection Ratio Formula

Common Mode Rejection Ratio of BJT Example

Common Mode Rejection Ratio of BJT Solution

Common Mode Rejection Ratio of BJT Formula Elements

Other Formulas to find Common Mode Rejection Ratio

Other formulas in Common Mode Rejection Ratio (CMRR) category

How to Evaluate Common Mode Rejection Ratio of BJT?

FAQs on Common Mode Rejection Ratio of BJT

Variable Name

GoCommon Mode Rejection Ratio Formula